I'd like to make a new topic, did a quick search but there is not a similar one...
So I think it's quite useful to have all the voltage multipliers posted here...
As I wrote in the Valvy topic, here --> http://www.diystompboxes.com/smfforum/index.php?topic=63479.msg597319#msg597319
I wanted to try this circuit here --> http://w1.859.telia.com/~u85920178/power/vconv_01.htm
with 4 trannies and a low number of caps and diodes...
It works, altough I didn't put this circuit in a tube pedal like the valvy yet, I built it successfully, now I got 49.8V from the 14V I got from my unregulated wall wart - did I tell you I finally got a DMM?! ;D
I believe it will find a good use in a tube project!!!
Here it is, mine has just a stage less to get that 48V
(http://w1.859.telia.com/~u85920178/power/vconv_comp.gif)
Nice! Well done - and I'm eager to see what you marry it up to (hint: try powering your Valvy's plates from it - no more gain but a massive boost!).
And you finally got a DMM!
http://www.cosmicrays.org/muon-%^&*roft-walton-calculation.php
http://www.diystompboxes.com/smfforum/index.php?topic=73905.0
http://www.diystompboxes.com/smfforum/index.php?topic=73808.0
http://www.diystompboxes.com/smfforum/index.php?topic=70582.0
http://dustbunny.physics.indiana.edu/~paul/cwbase/
http://www.techlib.com/files/voltmult.pdf
Yes Rick, I think my next Valvy will have this one inside...
(http://www.aronnelson.com/gallery/main.php?g2_view=core.DownloadItem&g2_itemId=38663&g2_serialNumber=1)
That looks like a great, cheap solution (though I don't know what the trannies cost). I am going to have two tube projects going on soon, so it will be interesting to see what power solution will work best.
I bought the trannies @ Banzai online store - 0.14 euro each, so 0.56 euro of trannies...
;D
LOL!!! I've seen some of your work and the sheer number of projects I'm amazed that you NOW have a DMM ;D
By the way, the power booster...nice. Any idea how much current it will supply?
Quote from: punkin
;D
LOL!!! I've seen some of your work and the sheer number of projects I'm amazed that you NOW have a DMM ;D
Yeah, Just because I found one at Porta Portese from a chinese...4 euro and that's it!
Luckily I didn't need one before, and even now it's not mymain tool, but you know it's useful in situations like that!!!
I an be sure that this multiplier works and how much voltage I do get!!!
Quote from: punkin
By the way, the power booster...nice. Any idea how much current it will supply?
Actually you can read all at the link I posted above...
Hello everybody...Found this googling around and thought it would be helpful to someone...
regulated high voltage power supply that runs from a 9V battery (http://www.galacticelectronics.com/HighVoltBatterySupply.HTML)
Quote from: Renegadrian on March 19, 2009, 12:12:23 PM
Hello everybody...Found this googling around and thought it would be helpful to someone...
regulated high voltage power supply that runs from a 9V battery (http://www.galacticelectronics.com/HighVoltBatterySupply.HTML)
Output 400v to 1000v !!!!!!!!
I can't get this thing to work. The 50hz oscillations explained on the page aren't happening. What could be wrong? The schematic on the page looks to me like it's connected differently from the component overlay and pcb. Which of these is right?
which schem you mean???
Renegadrian, I mean the schematic on the page you pasted in your first post. But never mind, they are the same - I just interpreted it wrong. But still, I can't get it to work :( Are the negative treminals of the 10u caps connected together? Mine are.
Yes, Jouni, if you downloaded the full zip file you have the pcb, where you can clearly see a line that connects the emitters of the 547/557 and the - of the 10µF caps. If it doesn't work, that's not the reason...
here is the section from a paia kit that makes 45v from a 15v dc and uses a cmos hex inverter and is used in the paia kit to power a 12ax7 tube ....
(http://i13.photobucket.com/albums/a300/mr_sevs/chargepump.jpg)
cheers
Polish anyone?! What is written here??? Does it work with 12V AC, not DC? Can it be useful for our projects?!
(http://www.port80h.com.pl/img/em80_zasilacz.jpg)
Taken from HERE (http://72.14.221.132/translate_c?hl=it&ie=UTF-8&sl=pl&tl=en&u=http://www.port80h.com.pl/articles.php%3Flng%3Dpl%26pg%3D82&usg=ALkJrhh8Z-K1XTqhyBcrNQ-eMfG9AFXzHA)
AC.
Quote from: snap on March 26, 2009, 05:18:28 PM
AC.
Yeah the inputs are AC, it would probably take an in-phase and an out-of phase input from a NPN/PNP complementary output pair like the one Adriano linked to in the first post.
Quote from: Ripthorn on February 07, 2009, 12:28:19 PM
That looks like a great, cheap solution (though I don't know what the trannies cost). I am going to have two tube projects going on soon, so it will be interesting to see what power solution will work best.
I'm sure the electros are more than the trannies. Does this handle higher current demands than a charge pump?
I've been gathering the parts (and the guts) for this SPMS: http://www.ledsales.com.au/kits/nixie_supply.pdf
I just finished breadboarding and testing it. I'm able to dial in voltages from 99 volts to 199 volts with the trimpot. 8)
After a while of running with no smoke/fumes/flames I decided to hook it up to my Sub Zero PP tube amp (http://www.diystompboxes.com/smfforum/index.php?topic=74786.0), the two work perfectly together, I'm really pleased. Under load the SPMS dropped from 195 volts to 185 volts. There's no sign of sag or compression.
I've made a document with the schematic, pinouts for the semiconductors and the part number for the inductor I used:
(http://i210.photobucket.com/albums/bb292/frequencycentral/NixieSMPS.jpg)
Cool project--and it doesn't even need a heat sink!
Well, while looking at a project on "the other forum" I found this schem. It is the switching power supply for the blackstar ht dual pedal and gets upwards of 300V to drive 12a_7's, etc. Check it out, it looks very simple yet functional. I haven't priced parts for it yet, however.
Edit, it's not letting me post the whole thing, the ... should be the "other" forum, add that to http://....org/members/bajaman/Baja/Blackstar/Blackstar%20HT%20power%20supply.png.
Quote from: Ripthorn on March 31, 2009, 09:39:16 AM
Well, while looking at a project on "the other forum" I found this schem. It is the switching power supply for the blackstar ht dual pedal and gets upwards of 300V to drive 12a_7's, etc. Check it out, it looks very simple yet functional. I haven't priced parts for it yet, however.
http://....org/members/bajaman/Baja/Blackstar/Blackstar%20HT%20power%20supply.png (//http:///members/bajaman/Baja/Blackstar/Blackstar%20HT%20power%20supply.png)
I'm getting a dead link.
yeah you have to add the domain by yourself...
lol...
I have a blackstar pedal and have had a look at the voltage multiplier circuit and it looks to work the same way as most smps with a mosfet switching the inductor to generate the HV. I have not traced it out myself, i would like to see this schematic but haven't a clue what " the other forum" in the link is, can anyone help , :icon_smile:
free stompboxes.org without that space
I found this while looking around today. It uses the 555 timer in a similar configuration to the Nixie tube driver. Instead of being just a boost converter, it is a flyback boost converter. It isn't really adjustable, but its something different to look at.
http://www.supertex.com/pdf/app_notes/AN-H36.pdf
I came across this information on flyback smps and thought i would post it in case anyone wants to know about these HV psu's
http://www.dos4ever.com/flyback/flyback.html
I've been using the nixie tube design for a long time and get 298v no load and 270v under load. There are two key points to remember; 1. The lower the 'on' resistance of the MOSFET, the higher the voltage. 2. Current handling and (therefore) output voltage are highly dependent upon the inductor. I wind my own on ferrite rod, which measure 150mH and take about 10 minutes to make.
The diode HAS to be a fast recovery type - a 1N4xxx will not work in this circuit.
Also, the 2.2uF cap is better replaced by a larger value - I've always used 47uF, but it depends what you're hanging off the end. I also use a 2.5k trimmer for VR1.
An interesting aspect of the design is that the ripple is ultrasonic, so as long as the input is well smoothed you get much reduced hum compared to conventional PSU designs. I use 12v, 4A switched-mode laptop PSUs. This circuit generates high peak loads on the supply and for best results use a minimum of 2A, 12v DC.
The shocks off this are the same as any high voltage supply - don't think that because it's fed from 12v it's any kinder - the output from this really smarts!
Quote from: Mick Bailey on April 01, 2009, 02:06:08 PM
I've been using the nixie tube design for a long time and get 298v no load and 270v under load. There are two key points to remember; 1. The lower the 'on' resistance of the MOSFET, the higher the voltage. 2. Current handling and (therefore) output voltage are highly dependent upon the inductor. I wind my own on ferrite rod, which measure 150mH and take about 10 minutes to make.
The diode HAS to be a fast recovery type - a 1N4xxx will not work in this circuit.
Also, the 2.2uF cap is better replaced by a larger value - I've always used 47uF, but it depends what you're hanging off the end. I also use a 2.5k trimmer for VR1.
An interesting aspect of the design is that the ripple is ultrasonic, so as long as the input is well smoothed you get much reduced hum compared to conventional PSU designs. I use 12v, 4A switched-mode laptop PSUs. This circuit generates high peak loads on the supply and for best results use a minimum of 2A, 12v DC.
The shocks off this are the same as any high voltage supply - don't think that because it's fed from 12v it's any kinder - the output from this really smarts!
Hi Mick
Thanks for the info. Can you tell me what specifically what you have changed in the circuit re the lower the 'on' resistance of the MOSFET to get the voltages you mentioned? A bigger than 2.2uf cap will just give a smoother voltage right? Whats the benefit of using a 2K5 trimmer instead of 1K - just easier to tweak the right voltage?
I can second your comment about respecting the HV output of this circuit, having given my thumb a little belt of 200 volts! Ouch!
This is from my "Sub Zero" thread:
Quote from: frequencycentral on March 30, 2009, 07:44:36 PM
Another thing about the SMPS, I've been leaving it running for hours hooked up to the amp. I went back to it yesterday to find it humming slightly at 195 volts, I turned it down to 190 volts and the hum went away. I don't seem to be able to get it back after hours of running at slighly lower voltage, which is a good thing!
I've noted what Mick Bailey said:
Quote from: Mick Bailey on April 01, 2009, 02:06:08 PM
This circuit generates high peak loads on the supply and for best results use a minimum of 2A, 12v DC.
I was actually running mine (plus two submini tubes) off a 12v 500ma adapter (which actually gives out around 700ma). Today I hooked the Sub Zero up to a 12 volts / 1.5 amp bench supply. I noted immediately that I was able to dial in much higher voltages - up to 230v. I'm guessing that even higher is possible by reducing the 470R resistor. So the hum I mentioned in that quote above was the SMPS loading the supply. It seems that the higher the voltage output the higher the current draw. After 5 minutes of running at 230v either the inductor or the IRF740 burned out (not sure which, though I'm guessing the inductor, as the IRF740 is rated at 400v. Maybe the inductor burned out and took the IRF740 with it, both got really hot). I replaced them both and am now running at 195v without any hum from the bench supply. It seems that I need to upgrade my inductor - any ideas?
EDIT: Do you guys think I should start a seperate nixie SMPS thread, as a few of us are working on this so we could compare notes, and I don't want to hijack this thread?
A separate Nixie thread would probably be a good idea. Interesting what you noted, though. I wonder if maybe you fed too much current through your inductor.
The comment about the MOSFET 'on' resistance is if you decide to experiment with different types. It needs to be below 0.5 Ohm, otherwise the circuit drops off in efficiency but make sure the voltage and current rating are adequate. The IRF740 is fine, but really does need heatsinking for valve audio projects. Note that the tab is at input voltage (12v) so it needs insulating if you decide to use the case as a heatsink.
My inductors are made as follows -
You need a 1" length of 3/8" diameter ferrite rod. I cut mine off longer lengths by nicking round the rod (use a Dremel cutting disk, saw or file) and snapping it off sharply. Use a drill chuck or vice to hold the short end.
Have ready a slightly longer piece of heatshrink tubing that is an easy fit over the rod (about 1/2" inside diameter is fine).
Take a length of 24 SWG enamelled wire and after leaving about 2" as a tail place a narrow piece of masking tape to hold it in place while you wind the wire round the rod to the other end and back. Hold this end with a small piece of tape and heatshrink the lot. The idea is you get two layers of turns on the rod. Note that I'm in England and SWG is different from AWG.
This results in a reliable inductor that runs cool and has low resistance.
My ferrite comes from stocks pulled from old transistor radios over the years - it always seems to be 3/8".
The bigger trimmer was determined by experiment to arrive at a higher voltage that would still adjust down if required.
Increasing the 2.2uF cap was purely to get rid of excessive sag on power chords. I found that bass response also improved, but this is down to what you're running off the supply.
I can say that I've found this circuit to be infallible, but the inductor has to have the current handling capacity and optimum value in order to get the output current and voltage required.
When you take a look at how the circuit operates the 12v is being shorted to ground through the inductor and the series resistance of the MOSFET, so you can appreciate the need for a fairly robust inductor. The small inductors usually recommended for Nixie supplies will not work for valve projects.
Thanks Mick,
some great info there on the inductor. Im about to start ordering some components for the psu to have a go building one. One question i have on winding your own inductors is how do you measure the uH value. (not sure if my DVM does H, i will have to have a look)
Well I don't really fancy rolling my own inductor, so I'm on the search for a suitable replacement. The one I used was this one:
Rapid part number: 88-1630 MIN RADIAL INDUCTOR 100UH RC, 11mm x 6.5mm (Low current) £0.47
http://www.rapidonline.com/productinfo.aspx?&tier1=Electronic+Components&tier2=Inductors+And+Chokes&tier3=Leaded+Inductors&tier4=Low+current+radial+lead+inductors&moduleno=64730&catref=88-1630&kw=88-1630
I have found that it's suitable for voltages up to ~190v, and I would estimate that at those voltages it draws ~400ma. The data shet say it handles up to 1.5 amp, so I don't know why mine burnt out.....?
----------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------
I've been looking at this One:
Rapid part number: 88-1003 HIGH CURRENT BOBBIN INDUCT 5.4A 100UH RC
It's way more expensive at £2.64, and physically larger at 14mm x 26.4mm, but would be unlikely to go into meltdown as it handles up to 5.4 amps.
http://www.rapidonline.com/productinfo.aspx?tier1=Electronic+Components&tier2=Inductors+And+Chokes&tier3=Leaded+Inductors&tier4=High+current+inductors&moduleno=72640
----------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------
Just looking at gut shots of the Nano head and the JJS Class A, they both seem to use something like this:
Rapid part number: 88-2883 77A SUPPRESSION COIL 100UH RC (11mm x 26mm) £0.52
http://www.rapidonline.com/Electronic-Components/Inductors-And-Chokes/Leaded-Inductors/High-current-leaded-suppression-chokes/79278/kw/
.....which is actually a choke. Hmm so what's the diff between a choke and an inductor?
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I'm pretty happy withe the SMPS I have right now using the first inductor I linked to, as the maximum voltage output (and it's current draw) suit the tubes I'm planning to use it with. But I reckon it would be cool to make a super small SMPS powered amp with a full size dual triode (12AU7 say) and a full size pentode (EL84?) running at ~250 volts, so it would be nic to develop this nixie SMPS to do the job.
A choke is just another kind of inductor. A choke is usually a term for an inductor that filters out something you don't want, like RF noise.
These are the inductors ive ordered from rs they work out at about £0.95 each, i will be experimenting as soon as all the bits turn up.
http://uk.rs-online.com/web/search/searchBrowseAction.html?method=getProduct&R=3963493
Quote from: Ice-9 on April 02, 2009, 06:13:43 PM
Thanks Mick,
some great info there on the inductor. Im about to start ordering some components for the psu to have a go building one. One question i have on winding your own inductors is how do you measure the uH value. (not sure if my DVM does H, i will have to have a look)
I originally used a very simple circuit with a scope http://images.google.co.uk/imgres?imgurl=http://www.edn-europe.com/cmsimages/0507/64f1.jpg&imgrefurl=http://www.edn-europe.com/cheapandeasyinductancetesterusesfewcomponents%2Barticle%2B1480%2BEurope.html&usg=__tXlNxZ34KPTWnRgqtnlE8IRViX0=&h=444&w=588&sz=38&hl=en&start=16&um=1&tbnid=37t2pg7dckHUgM:&tbnh=102&tbnw=135&prev=/images%3Fq%3Dsimple%2Binductor%2Bmeasurement%26hl%3Den%26safe%3Doff%26sa%3DN%26um%3D1 (http://images.google.co.uk/imgres?imgurl=http://www.edn-europe.com/cmsimages/0507/64f1.jpg&imgrefurl=http://www.edn-europe.com/cheapandeasyinductancetesterusesfewcomponents%2Barticle%2B1480%2BEurope.html&usg=__tXlNxZ34KPTWnRgqtnlE8IRViX0=&h=444&w=588&sz=38&hl=en&start=16&um=1&tbnid=37t2pg7dckHUgM:&tbnh=102&tbnw=135&prev=/images%3Fq%3Dsimple%2Binductor%2Bmeasurement%26hl%3Den%26safe%3Doff%26sa%3DN%26um%3D1)
This is very accurate, reliable and easy to build. I then bought an LCR meter from Hong Kong - about £7 plus postage. I like the meter, but I like the scope method even better as it is more accurate and has a greater range.
Sorry, I just noticed in my earlier post I said 150mH, Should be 150uH
Rick
Re: Rapid part number: 88-2883 77A SUPPRESSION COIL 100UH RC (11mm x 26mm) £0.52
This would be my choice - I've got some of these in 150uH but have not tried them yet. Current handling and DC resistance seem good and I chose these as the best commercial match to my own DIY inductors. The circuit is sensitive to inductance dependent upon load and it's worth getting a few values due to the low cost/high postage ratio and playing about with them.
BTW, I've found that 100uH causes heavy current draw without increasing the output voltage and causes excessive load on the MOSFET. Very high open circuit voltages can be achieved by increasing the inductance even more, but the impedance then increases and therefore the on-load voltage reduces. I've built a lot of these circuits and now always use 150uH
Thanks Mick, I'll order some of those in different values. You appear to be our resident expert on the nixie SMPS - it's good to have your input, and it's given me plenty of inspiration to continue expermenting with it.
I'm also very curious as to what you use your SMPS's to power???
I use these mainly in hi-fi valve pre-amps. The high voltage gives more headroom and the current capability gives better output swing to drive the power tubes. I started using this idea due to the relatively high cost of suitable power transformers in the UK and to improve signal to noise characteristics. It also meant a real saving on space.
I've also built quite a few pedal-based guitar pre-amps that are straight lifts of classic amp circuits. These don't tend to work very well at low voltages 'as-is' and often need modifying for (say) 30v operation. When you've got up to 300v to play with you can get the necessary dynamics back to capture at least some of the original sound.
BTW, I first saw these circuits in the '70s in an electronics magazine to power a small-to-medium florescent tube for camping. I still have one of these somewhere as an experiment from my youth, built on a piece of bent aluminium sheet. It worked superbly when powered from a small motorcycle battery. It used a pair of transistors in free-running astable mode instead of a 555 and with no regulation/feedback to limit the voltage. If you disconnected the load the voltage shot up and fried the switching transistor.
Wonder when the SMPS idea was first used for guitar pedals?.....................
After a bit of a disater (was decorating house and accidently threw out most of my electronics paperwork) I'm getting back on track , this is the HV SMPS i'm working on at the moment and its a design using the MAX1771, it should supply about 220V at 50ma.
I have most of the components needed but am waiting on a couple to arrive so i thought i'd start the pcb making. Ther following pics are of the schematic, PCB and PCB overlay. I hope to complete and test the circuit early next week.
The next update to the circuit is going to be a saftey device. If you check the schematic pin 4 of the max chip is tied to ground, but if its switched to Vcc then the chip will shut down preventing the HV getting to the output. I will be putting a push to make switch and a resistor in there so that when the base of the enclosure is removed it will disable the HV. I have a few other things to work on with this but would like to post what i have so far.
I also have the pcb files for printing if anyone wants them i can post them up. The size of the pcb is about 30mm x 35mm
(http://i90.photobucket.com/albums/k243/lenny1dog/schematic.jpg)
(http://i90.photobucket.com/albums/k243/lenny1dog/overlay.jpg)
(http://i90.photobucket.com/albums/k243/lenny1dog/pcb.jpg)
So Mick, Rick and Mick, do you guys use multi turn potentiometers for your VR1? That seems to be a good idea, but I am wondering if it is worth it.
Hi Brian, I have went for the multiturn pot in this for two reasons, firstly i think it will be more accurate to dial in the voltages and secondly they seem a lot solider than the single turn trim.
these are the ones i got http://uk.rs-online.com/web/search/searchBrowseAction.html?method=searchProducts&searchTerm=521+9798
I use standard cermet pots with no problems at all, the only reason being that I have plenty of them. You can also temporarily wire in a pot, set the on-load voltage then read off the value and replace the pot with a fixed-value voltage divider. In most cases you'll find that the pot is set to its maximum travel anyhow.
you could always take out the VR and have the voltage at a set level. In the schematic i have posted above you can keep R3 value at 10K, put a link in for VR1 and adjust the value of R2, a simple equation for this is
R2= (6.7 * Vout) Kohms
R2=(6.7 * 220)
R2= 1474 or 1M5
So for 300v output, (remember you would need to change the ratings of other components as i have only put in max ratings of 250v for some caps
R2=(6.7 * 300)
R2=2010 or 2M
the full equation is R2=R3 * (vout\1.5)
Hi
a couple of comments...
A 555 is a very efficient oscillator for these things. The bipolar version can source up to 200mA (!). Another option would be an LM386 set up as an oscillator.
The fellow who used an 8 ohm:1 kohm transformer is a genius. That should give about a 10-fold increase in voltage (square root of 1000/8 minus losses).
An astable 555 will output about 7 V p-p from a 9.5V supply, and that can be boosted to about 60 or 70V p-p by the transformer. From there you only need 2 charge pumps (voltage "doublers") to get to a usable voltage (somewhere between 120 to 200 V DC at 2 or 3 mA). I *think* that's enough to run a few 12AX7s. Of course, you'll want a decent 9V battery (preferably NiMH), as power consumption will be quite high (This is true of all these designs).
I notice that the first design used 220uF caps. That seems excessive and expensive, especially for the last stages where the current is only a mA or two. Above 50 V, my calculations indicate that you only need 5 to 10uF of storage. You'll lose a tiny amount of efficiency, but save $$$.
cheers
NB the frequency response of those audio transformers is very limited (due to their small core, capacitances, etc). It will need to run at about 1kHz to be effective. Unfortuantely, that'll spray some electro-magnetic noise around at a mid-audio frequency. Some shielding, especially over the transformer, might be called for.
did you guys ever consider something like this?
(http://www.aronnelson.com/gallery/main.php?g2_view=core.DownloadItem&g2_itemId=3778&g2_serialNumber=2)
it's the little driver that you need for backlighting on displayes. with 5 volt in ( the regulator is soldered on the back in the pic) I get 70Volt AC out. efter rectideing I get 100volt dc..
the teleplug is for size reference
j
Okay, I am way interested in that. Is the max input voltage 5V? And where would you go about getting one and roughly what does it cost?
Quote from: Ripthorn on April 08, 2009, 01:51:18 PM
Okay, I am way interested in that. Is the max input voltage 5V? And where would you go about getting one and roughly what does it cost?
+1! Tell us more.....
+ another 1, defo tell more, how much current can it deliver ?
It seems we're all interested...Yeah, tell us more!!! :icon_wink:
THIS ONE (http://www.micro-examples.com/public/microex-navig/doc/150-p16f84-single-nixie-clock) seems pretty easy to build...
Quote from: frequencycentral on April 08, 2009, 01:57:45 PM
Quote from: Ripthorn on April 08, 2009, 01:51:18 PM
Okay, I am way interested in that. Is the max input voltage 5V? And where would you go about getting one and roughly what does it cost?
+1! Tell us more.....
you can find them at most of the big electronics component companies..for example www.elfa.se search for part number 75-559-49 or electroluminence panel voltage converter. they usualy want 3-5volt dc in and you buy them according to how much current you need. often you find them under opto/display/backlight in the catalogues.
cost is around 10 euro
j
Hi
about a year ago I looked at luminescent panel drivers.
All of the reasonably priced ones had firly low current capacity. *maybe* enough to drive a 12AX7 stright into a JFET buffer with a couple of megohms of impedance, but maybe not, too.
For a while (since 2003) there's been a 12V wallwart-powered 12AX7 pre-amp kit available here in Oz. http://www.siliconchip.com.au/cms/A_30804/article.html (http://www.siliconchip.com.au/cms/A_30804/article.html)
I bought the article way back, and if I recall correctly, it used a DC to AC converter chip and a step-up transformer (switching?) so that the final size of the box was quite small.
I still think you could do a lot with an astable 555, 1k:8 transformer and a bridge (about 100V DC without a charge pump stage). All in about 2 inches by one inch of PCB.
cheers
http://www.tube-tester.com/sites/nixie/nww/nixie-watch.htm
Wow, this thread has turned up some wonderful ideas and links
That is one well wound inductor, It would probabally take longer for me to wind that than it would to learn to play the entire collectoion of beatles song.
That inductor is a piece of art in its own right.
Iv'e been working on this PSU now for a while and the rest of the components have arrived so i have made up the PSU. I'm powering the lot from a wall wart AC adapter and it should work with an input anywhere from 9v-18v, I'm getting 230v out of it as the picture shows.
This is a PSU for a project i'm working on and has +/- 15v DC to power opamp circuits, 12v Dc at 1A to power tube heaters and 230v Dc to power the valve plates all built in, The PCB also houses the footswitch led and jacks. I will do some testing under load and may try to get about 270v on the output by changing the feedback potential divider top resistor to about 2M instead of the 1M5 i have there now. (I will do the maths first).
Anyway here are some pics now showing what i have so far.
(http://i90.photobucket.com/albums/k243/lenny1dog/230f.jpg)
A pic from the top of the PCB showing most components
(http://i90.photobucket.com/albums/k243/lenny1dog/230v.jpg)
With meter connected showing the 230v output
(http://i90.photobucket.com/albums/k243/lenny1dog/230b.jpg)
Showing the bottom of PCB with inductor and PWM chip
(http://i90.photobucket.com/albums/k243/lenny1dog/230bclose.jpg)
Showing the inductor and stuff up a bit closer.
Mick that looks excellent, and that SMD MAX1771 is tiny! The inductor looks like it will handle the ma too.
Rick the inductor is rated at 2A so should be ok. I now need to be testing with some valves but it will be a few days before i can do that.
My only switched inductor power supply experiment so far has been a simplified version of the one frequencycentral posted, but with a BS170 ( :icon_eek: ) as the MOSFET. Small changes in the circuit can make big changes at the output. I over-volted the output cap for the split-second it took the voltmeter to show what was going on! Luckily, no explosions. :)
The thing I noticed though is the switching frequency spewed all over the place. I could just hold my scope probe near (1-2cm) the inductor and get large (many mV) current spikes. I think that may be a good argument for using shielded inductors/transformers.
For comparison purposes, the near-field HF radiation was not much better with a %^&*roft-Walton supply, which was somewhat surprising (but may have had something to do with long leads on the breadboard acting as antennae).
The best lesson I learned from these experiments is that if you have multiple high frequency oscillators in close proximity, it's nearly impossible to avoid problems. In the future, all my projects will have a single HF clock source.
Quote from: earthtonesaudio on April 15, 2009, 07:44:22 AM
The thing I noticed though is the switching frequency spewed all over the place. I could just hold my scope probe near (1-2cm) the inductor and get large (many mV) current spikes. I think that may be a good argument for using shielded inductors/transformers.
Shielding would help but the problem this would pose is shielding the inductor would drop the efficiency, by how much i'm not sure.
Yet another proposal for a 'not so high' high power supply for our tubes project ? Be carefull, it is NOT tested yet... just want your opinion on the design and components values (And as usual be carefull with high voltage...)
I was preparing my next parts orders and thought it would be nice to experiments with higher voltage tube experimentations ;) I plan to get the high voltage from a 12V AC / 1A EHX power adapter. I would like to be able to power up to 3 X12AX7 tubes in the 230V areas... with good filtering and with being isolated from power supply (thus the 12V EHX power adapter)
I took the inspiration from http://www.electricwestern.com/diytubes.html (http://www.electricwestern.com/diytubes.html) and from our king of the tubes (Frequency Central) designs ;)
Here is what I would like to try. Any comments ? I am not sure if I really need the inductor/ caps filtering on the LM317 part of the schematic
http://www.aronnelson.com/gallery/main.php/v/darkness_fx/Tube+Power+Supply.png.html (http://www.aronnelson.com/gallery/main.php/v/darkness_fx/Tube+Power+Supply.png.html)
Thanks ! :)
You flatter me sir! I'm no expert on transformers and power supplies, but it does strike me that you could simplify the heater supply by using a 7806 instead of the LM317. 6 volts is within the tolerance of the heaters, and you'll eliminate the trimmer, which could eventually fail or drift. One less thing to worry about! For my dual 6111 pedals I'm running the heaters at 6 volts (ok - two in series from 12 volts), it's fine. Though I understand why you might want the precision of 6.3v exactly.
You're welcome Rick ! It's always a pleasure to read from your tube projects ! :)
I was also thinking of just using the LM7806 for the power supply... but I was fearing that it would shorten up the tube life... but don't know how much :icon_razz: ??? Indeed, powering up/off the unit might be more harmefull for the tube life than the 0,3V difference ??? In first instance I might just try the LM7806 instaed of the LM317.
Thanks !
I don't think it should shorten their lives, it's within the spec. As I understand it, it's only heater voltages higher than the rated spec that will shorten their lives - in the long run. I can personally confirm that you can put 12 volts through the heater of a 6111 (oops) without killing it. They are tough little @#$%ers after all, designed to be shot up to 30,000ft in missiles......!!
Quote from: Darkness, Darkness on May 25, 2009, 05:53:31 PM
Yet another proposal for a 'not so high' high power supply for our tubes project ? Be carefull, it is NOT tested yet... just want your opinion on the design and components values (And as usual be carefull with high voltage...)
I was preparing my next parts orders and thought it would be nice to experiments with higher voltage tube experimentations ;) I plan to get the high voltage from a 12V AC / 1A EHX power adapter. I would like to be able to power up to 3 X12AX7 tubes in the 230V areas... with good filtering and with being isolated from power supply (thus the 12V EHX power adapter)
I took the inspiration from http://www.electricwestern.com/diytubes.html (http://www.electricwestern.com/diytubes.html) and from our king of the tubes (Frequency Central) designs ;)
Here is what I would like to try. Any comments ? I am not sure if I really need the inductor/ caps filtering on the LM317 part of the schematic
http://www.aronnelson.com/gallery/main.php/v/darkness_fx/Tube+Power+Supply.png.html (http://www.aronnelson.com/gallery/main.php/v/darkness_fx/Tube+Power+Supply.png.html)
Thanks ! :)
There have been a number of power supply schematics around the net recently, using a power transformer in reverse to obtain high voltage.
Please be aware that, unless the transformer is chosen very carefully, this format can be a recipe for Fire.
While
audio transformers can usually be used in either direction, power transformers are usually designed differently, depending on intended use as either step-up or step-down. When AC is connected to a winding that was originally designed as a step-down secondary, core saturation will often occur. When core saturation happens, the winding will no longer appear as an inductor. The input current will increase and the power will be dissipated in the DC resistance of the winding. The winding will begin to heat up, even if there is no load on the other winding. The heating can happen at quite low currents supplied by an AC plugpack. Some transformers have a thermal fuse built in to the mains (original primary) winding, but, when the original secondary is being used as a primary, the thermal fuse can not give any protection. If ambient room temperature is already high, the transformer can, over a number of hours, become hot enough to cause combustion.
The other, less serious, disadvantage of this practice is that, when core saturation occurs, the output waveform from the high voltage winding will be clipped and will therefore contain harmonics which will interfere with other circuitry, sometimes worse than a switch mode supply.
Guess you guys may have seen this, but weber has been selling this trafo for a while:
https://taweber.powweb.com/store/pdlptsch.jpg
specifically designed for tube pedals... not cheap though at $20
Google "Royer mxl2001 mod"
Look at the power supply section.
Can be adjusted and changed.
I have posted about this in the past IIRC.
Thanks for the feedback guys ! That's very interesting :)
I really like the idea of the Weber transformer specially desigend for that purpose 8)
So here is an update of the design (I have delete the previous version) http://www.aronnelson.com/gallery/main.php/v/darkness_fx/Tube+Power+Supply+3.png.html (http://www.aronnelson.com/gallery/main.php/v/darkness_fx/Tube+Power+Supply+3.png.html) If you have remarks...
At the moment size/cost is not an issue for me on this project (still working on Marshall like tube preamp ;D). I would prefer to use transformer solution as it seems less complex to build and should allow higher voltage and maybe a few more mA to power a few more preamp valves
Thx again !
Quote from: objectx on May 26, 2009, 11:33:39 AM
Guess you guys may have seen this, but weber has been selling this trafo for a while:
https://taweber.powweb.com/store/pdlptsch.jpg
specifically designed for tube pedals... not cheap though at $20
Thanks for posting that 8) I hadn't seen it before.
Quote from: Darkness, Darkness on May 26, 2009, 01:51:56 PM
I really like the idea of the Weber transformer specially desigend for that purpose 8)
So here is an update of the design (I have delete the previous version) http://www.aronnelson.com/gallery/main.php/v/darkness_fx/Tube+Power+Supply+3.png.html (http://www.aronnelson.com/gallery/main.php/v/darkness_fx/Tube+Power+Supply+3.png.html) If you have remarks...
That looks neat and simple. It should work well.
Could a voltage multiplier like these be used to turn a Valvy into an amplifier since more voltage on the plates means more boost?
Quote from: bassmannate on May 26, 2009, 09:21:54 PM
Could a voltage multiplier like these be used to turn a Valvy into an amplifier since more voltage on the plates means more boost?
Yup: http://www.diystompboxes.com/smfforum/index.php?topic=73317.0
Quote from: Darkness, Darkness on May 26, 2009, 01:51:56 PM
Thanks for the feedback guys ! That's very interesting :)
I really like the idea of the Weber transformer specially desigend for that purpose 8)
So here is an update of the design (I have delete the previous version) http://www.aronnelson.com/gallery/main.php/v/darkness_fx/Tube+Power+Supply+3.png.html (http://www.aronnelson.com/gallery/main.php/v/darkness_fx/Tube+Power+Supply+3.png.html) If you have remarks...
At the moment size/cost is not an issue for me on this project (still working on Marshall like tube preamp ;D). I would prefer to use transformer solution as it seems less complex to build and should allow higher voltage and maybe a few more mA to power a few more preamp valves
Thx again !
There is not much details on weber website about the characteristics of this transformer, but I wander if I should not have to power the heaters separately (=not from the same EHX 12VAC 1A power supply) :
-> if output is 260VAC 40 mA, then the transformer is 10VA. Then, if I am not wrong, the 12VAC input would then draw around 870mA... Am I right ? In that case there is not enough mA left for powering 3 tubes heaters from that power supply as I intend to, and I have to adapt the input fuse value too
Quote from: Darkness, Darkness on May 27, 2009, 06:55:50 AM
-> if output is 260VAC 40 mA, then the transformer is 10VA. Then, if I am not wrong, the 12VAC input would then draw around 870mA... Am I right ? In that case there is not enough mA left for powering 3 tubes heaters from that power supply as I intend to, and I have to adapt the input fuse value too
The quoted 40mA is the
maximum that the secondary can supply, however, it will supply only what is drawn from it by the load. Each half of a 12AX7 will probably be drawing less than 2mA, therefore the total load on the secondary with 3 x 12AX7 will be 12mA, a total of 3.12VA or a primary current of 260mA.
Unfortunately, the heaters and the 6V linear regulator will consume more than 11VA because linear regulators are very inefficient. I don't understand why you want to regulate to 6V (or 6.3V) when the 12AX7 is designed for 12.6V heater supply. Alternatively, if you really want to run the heaters at 6V, you will need either a 12VAC 2A adaptor or use a switching regulator such as the LM2575T-ADJ for the 6V supply instead of the linear regulator.
Thanks a lot ClinchFX :)
You're right about the heaters at 12V... For the heaters I was still stuck with my 6111 tube tests...12AX7 have different heaters value :icon_redface:
Quote from: Darkness, Darkness on May 28, 2009, 06:10:10 AM
Thanks a lot ClinchFX :)
You're right about the heaters at 12V... For the heaters I was still stuck with my 6111 tube tests...12AX7 have different heaters value :icon_redface:
Thanks. Re-reading my post, I apologize if I sounded like a smartass. I didn't mean it that way. At times I become very involved in the technicalities and forget to be human :-[
I'm just glad to help.
Peter.
No matter ;) You've been very helpfull. Thanks again :)
Fabien.
I found this over at AX84 forum, thought it may be useful to some folks:
PDF: http://ricktone.rickcampbell.org/cgi-bin/getimg.cgi/PedalPowerSupplyLayout.pdf
Link to thread: http://www.ax84.com/bbs/index.php?id=385353
The linked two transformer supply is missing bleeder/balance resistors, also you need to be mindful of the first and second VA ratings of the transformer. Fred N. used a supply like that for a project that has been on the web for some time IIRC.
Did you google the Royer mxl2001 mod yet?
Quote from: Gus on May 31, 2009, 10:12:53 AM
Did you google the Royer mxl2001 mod yet?
Tkanks Gus. I had a few difficulty to get the schematic but it is all the more interesting as I would like to try these on of these days tube mod for mics :)
If someone is intesrested (you should!) here is the article PDF link http://www.diyfactory.com/projects/royerproject/royermod_2.pdf (http://www.diyfactory.com/projects/royerproject/royermod_2.pdf)
This power supply, proving 95VDC is interesting for the subminis. For my current tube project (Marshall preamp clone), I still prefer the Weber transformer idea, because it provides almost out of the box higher voltage, closer to the voltage of the Marshall preamp
Ok, question time:
I'm running the nixie SMPS that I posted on page 1 of this thread. I've got it hooked up to a small amp, basically a Firefly using a 6112 and a 7327. The two tubes' heaters are in series, so that's 300ma current draw. I'm using a 12 volt regulated wallwart that's rated at 500ma, but I know by experimenting that in reality it gives out more like 700ma. The more voltage you ask of the SMPS, the more current it draws. I've been 'soak testing' it all afternoon, I've left it on and keep coming back to it to check it's not on fire (!). You can tweak the trim pot just back from where it starts to hum because it's asking for more ma than the wallwart can give. Periodically, I have to tweak it back, as half an hour later it will be humming when it wasn't before. I started out at 206 volts, now I'm down to 186 volts. So what's happening here? It seems to me that the longer I run it for the lower the voltage it will supply, though it seems to have bottomed out at 186 volts. I realise that I could use a higher rated wallwart and teh problem would go away, I just want to understand what's going on.
Anyone?
Unless you have a heat dissipation problem the output should remain constant. My own amps don't drop voltage at all, but I had to both heatsink and fan cool the switching transistor as well as run the PSU off a 4A supply. If your transistor is not overheating, check that the wallwart power supply is not suffering from thermal overload.
I have the IRF740 screwed to a big aluminium heatsink 3" x 4" with vents - far too big for the build I'm planning. I'll try another (more thermally conductive?) heatsink. What sort of heatsinks do you use Mick, size and material? Also, my SMPS is still on breadboard, so is it possible that the capacitance of the breadboard itself is causing issues. I'll also try a higher rated bench supply, just to check that it's not thermally overloading my wallwart. The storage cap I'm using is the 2.2uf specifed in the nixie SMPS schematic, I notice you use 47uf. While I don't think this is the source of the problem, I should use a bigger cap to smooth things out I guess.
Hi
QuoteI have the IRF740 screwed to a big aluminium heatsink
What type of heat transfer compound/washer are you using? MOSFETs are unique in that they conduct less when hot (unlike BJTs that suffer thermal runaway).
Uou probably know this, but I'll state it for the new folk: it's often the thermal resistance at just one junction that causes the problems. Heat transfer is only as good as the weakest link. (Thermal resistances are just like series electrical resistances - one high resistance ruins conduction through all of the low resistances.)
cheers
Brett, I'm a noob regarding heat dissipation. I just screwed the IFR740 to a big aluminium heatsink. :icon_redface:
What do I nned to do to get this right? Transfer compound? Washer? Not quite sue about what to do re . "it's often the thermal resistance at just one junction that causes the problems" - any enlightenment greatly appreciated!
Hey Rick, your solder is not high thermal resistance (as we know) but if heat is anything like electricity, when you match up your mosfet to your heatsink, you could have an impedance mismatch, which minimizes heat transfer. You could get something like Arctic Silver thermal compound which is really good stuff (I have both the compound and the epoxy and both work great). I used it for mounting my regulators in my submini amp to the chassis and it works much smoother now (and the chassis only gets mildly warm as opposed to the heatsinks which got blazing hot). Hope that helps.
Really interesting reading here. Ill be picking up the parts for the Nixie psu tomorrow. Ive been trying to make a small tube amp for a while now but with only 48v dc not had much luck. About connecting two transformers like FC posted on pg4, is that safe? Ive got two identical transformers 240v primaries and the secondaries are multitapped for 12,15,17.5,20,24,27.5,30 volts (30VA) 1amp. Is it possible to connect them together to get higher voltage?
Hi
Quotebut if heat is anything like electricity
Yep, heat transfer is very much like electricity transfer (and good electricity conductors, such as metal, are usually good heat conductors). Your problem might be that air is a really bad conductor (of heat and electricity). That's why your computer has a fan - to overcome the poor conduction of air by adding lots of convection. In your case, you're not putting a fan in your device, so you need to excluse as much air as possible from between your MOSFET and the heatsink. A thermally-conductive grease or thermally conductive plastic/rubber washer does the trick.
cheers
PS the maths are easy. Thermal resistances (degrees Celcius (C) or Kelvin(K)/W) can be treated like series resistances (volts/amp). If your MOSFET has 1C/W resistance(from the junction to the metal backing) and the heatsink is 10C/W (fairly big) and the junction 20C/W (fairly bad), then the total resistance is 31 C/W. Generally, you want the juction to be less than 100 C hotter than the surrounding air (Si melts at 150C). So, in this case, the MOSFET and heatsink can safely dissipate 100C/31 C/W = 3.3W. But if you install a better junction (5 C/W instead of 20 C/W), the total resistance is 1+5+10 = 16 C/W, the total dissipation can be 100 C/16 C/W = 6 W (amost twice as much). Because junctions are often poor conductors (high thermal resistance), it's usually best to improve it before you go replacing a smallish heatsink (10 to 20 C/w) with a monster (2 C/W). Also, adequate ventiation of the box (slots/openings etc) really helps keep the air cool, allowing for smaller heatsinks and poorer junctions.
Heres a pcb for the nixie psu. "NOT VERIFIED" please cast your eyes over it.
(http://www.diystompboxes.com/Users/johngray/Desktop/nixie%20psu.JPG)
Crap that didnt work let me try again. NOT VERIFIED(http://www.diystompboxes.com/Users/johngray/Desktop/nixie%20psu.JPG)
dam it didnt work again
Quote from: JOHNO on August 13, 2009, 06:00:26 AM
Really interesting reading here. Ill be picking up the parts for the Nixie psu tomorrow. Ive been trying to make a small tube amp for a while now but with only 48v dc not had much luck. About connecting two transformers like FC posted on pg4, is that safe? Ive got two identical transformers 240v primaries and the secondaries are multitapped for 12,15,17.5,20,24,27.5,30 volts (30VA) 1amp. Is it possible to connect them together to get higher voltage?
It is possible to get more than 240VAC on your HT line, but I would highly warn against it. Say for example your first transformer is pulling 10mA at your 24V tap. You connect that tap to your 12V secondary of the other transformer. In theory, that should give you 480VAC on the other side of your second transformer. Sounds good, right? The problem is that you can very easily blow the second transformer doing this because you are using a higher-than-rated secondary voltage, which is really stressing the core and windings on both sides of the transformer. Not only that, but you are also transferring twice the power, which means you may very easily get the first transformer in on the blowing up action. So, it is possible, but I don't recommend doing it.
Actually, with a multi-tap transformer like you just said, it should be safe as long as you don't exceed the power rating. My above explanation is primarily for single-secondary transformers. So in your case, yes you can, just be very careful about how much power is getting through each winding. You never want ti to exceed 30W, period.
I uploaded the PCB in the gallery. search for "nixie psu". I made some of the pads pretty large so as to suit a wide range of caps and inductors. ITS NOT VERIFIED. So you guys should check it closely for mistakes before you build on it. Hope its useful.
Opps just realized that the layout is reversed. Hmmm or is it? You guys will figure it out.
I use solid copper heatsinks bent from 16 gauge sheet with thermal compound used for PC processors. without a heatsink the MOSFET gets hot, voltage drops and it eventually dies.
The test for your heatsink is to run the PSU until you see the voltage drop, switch it off then feel if the transistor is hot. Should run just warm to the touch if all is well.
OK the PCB is verified. Getting 105 to 303 volts dc for the Nixie psu. Running it at 12 volts 500ma. The only thing that has me worried at the moment is that the circuit kind of whistles or buzzes. Anyone else experienced this? Only have it connected to the multimeter at the moment.
OK, I found a small heatsink on an old PC graphics card, I've scraped all the thermal compound onto the back of my IRF740 and attached it to the heatsink, and will do extended testing today,
Quote from: JOHNO on August 14, 2009, 12:33:28 AM
OK the PCB is verified. Getting 105 to 303 volts dc for the Nixie psu. Running it at 12 volts 500ma. The only thing that has me worried at the moment is that the circuit kind of whistles or buzzes. Anyone else experienced this? Only have it connected to the multimeter at the moment.
It whistles and buzzes? Weird. And it's not powering anything? Mine hums if I ask too much of it, but that's through the speaker.
Quote from: earthtonesaudio on February 07, 2009, 10:54:26 AM
http://www.cosmicrays.org/muon-%^&*roft-walton-calculation.php
http://www.diystompboxes.com/smfforum/index.php?topic=73905.0
http://www.diystompboxes.com/smfforum/index.php?topic=73808.0
http://www.diystompboxes.com/smfforum/index.php?topic=70582.0
http://dustbunny.physics.indiana.edu/~paul/cwbase/
http://www.techlib.com/files/voltmult.pdf
I just realized that the first and most important link in this post was screwed up by the forum's "bad word censor" software.
The part that says "%^&*roft" should be spelled "c o c k roft" (no spaces) as in the Nobel Prize winner. Pssh. :icon_rolleyes:
There were a number of tubes made for car radios which operated off 12 V filament and plate supplies. One of the more interesting was the 12K5 which was a space-charge grid tetrode (control grid operated at +12 V, input on the screen). The 12K5 was matched to an 800 ohm output impedance (so 600 ohm transformers would work) and has a 9000 micromho transconductance and a 40 mW output power.
There was a whole series of these tubes (about two dozen different types) with a maximum plate voltage rating of 30 V although a few were rated at 16 volts. The car radios all had germanium output transistor power stages, so no vibrator or transformer was needed. Many functions were represented including dual triodes, pentodes, diode-pentodes and diode-triodes.
This allows you to use tubes with only a 12 V supply for both filament and plate.
A verified layout for the Nixie SMPS, I just built and tested it today. It's putting out 313 volts without a load. I haven't added the snubber yet, I want to experiment with that part. The snubber is made up of the 2.2K resistor and the 100pF cap in the Nixie schematic. I've an idea that changing the snubber values slightly will keep the B+ higher, so I thought I'd build the main part and hook it up to my breadboard to test different filterings. I used two 100uF caps instead of the 330uF, mainly to save on space.
Here's the link to the original file again: http://www.ledsales.com.au/kits/nixie_supply.pdf
(http://i210.photobucket.com/albums/bb292/frequencycentral/555SMPS.gif)
(http://i210.photobucket.com/albums/bb292/frequencycentral/000_0002-2.jpg)
(http://i210.photobucket.com/albums/bb292/frequencycentral/000_0003-3.jpg)
Very nice!
Thats looking really good Rick, and 313v as well. Were did you get that inductor i think i will build this SMPS to try with one of my 12ax7 designs.
Quote from: Ice-9 on October 30, 2009, 05:05:15 PM
Thats looking really good Rick, and 313v as well. Were did you get that inductor i think i will build this SMPS to try with one of my 12ax7 designs.
Thanks guys. The inductor is this one: http://www.rapidonline.com/Electronic-Components/Inductors-And-Chokes/Leaded-Inductors/High-current-leaded-suppression-chokes/79278/kw/
The SMPS is for my next amp. I've got some 12AX7 and 12AU7 left over from my Valvecaster builds last year, and I bought a bulk lot of Fender Reverb Transformers (for my Murder Ones), so I thought I'd try a SE amp with 'proper big tubes' and a SMPS.
Just for fun, I connected the SMPS to a 9 volt battery today - and got 254 volts! I titter'd me t!ts off! Completely useless to consider a 9 volt battery powered tube amp though.
Quote from: frequencycentral on October 30, 2009, 05:15:48 PM
Just for fun, I connected the SMPS to a 9 volt battery today - and got 254 volts! I titter'd me t!ts off!
LOL! :D
Quote from: frequencycentral on October 30, 2009, 05:15:48 PM
Just for fun, I connected the SMPS to a 9 volt battery today - and got 254 volts! I titter'd me t!ts off! Completely useless to consider a 9 volt battery powered tube amp though.
Yeah ! but to get 254v from a 9v battery is just something you have to try just to see it for real. Lol
Here's a variation on the 555 SMPS with the addition of a negative charge pump section. Probably of interest to only one person on the planet (me), but developed so I can play with negative grid biasing my 5902 beam pentodes. Verified today on the breadboard. The red stars indicate where it is possible to tap off -11.5 volts and -22 volts, possibly useful for negative grid biasing other tube types.
(http://i210.photobucket.com/albums/bb292/frequencycentral/555SMPSNegative33.jpg)
Does this require a heatsink for the FET?
Quote from: earthtonesaudio on November 02, 2009, 07:34:22 AM
Does this require a heatsink for the FET?
Yeah, the IRF740 gets pretty hot. Without thermal dissipation it would eventually burn out I believe. I used the simplified version (ie without the negative charge pump) in my Superfly, there are pics of the heatsink I used in that thread: http://www.diystompboxes.com/smfforum/index.php?topic=78302.0
Hello Rick,
why did you move the 2K2/100p to the other side of the 1N4004?
Maarten
Quote from: maarten on November 04, 2009, 11:00:58 AM
Hello Rick,
why did you move the 2K2/100p to the other side of the 1N4004?
Maarten
Bummer! My mistake, I'll correct the layout and schematic...... :icon_confused:
It looks like a snubber circuit to me which goes in parallel with the FET's drain and source terminals. Or in this case, because you've got voltage-mode control, it goes from the drain to ground. These can increase efficiency in the FET by 20-30%, sometimes more with excessively ringing circuits!
Quote from: frequencycentral on November 04, 2009, 12:52:13 PM
Quote from: maarten on November 04, 2009, 11:00:58 AM
Hello Rick,
why did you move the 2K2/100p to the other side of the 1N4004?
Maarten
Bummer! My mistake, I'll correct the layout and schematic...... :icon_confused:
Ok, both the layout and schematic (above) are now corrected. You may need to refresh your browser to see them. Oops. :icon_redface:
thanks for sharing !
i'm curious,
how many mA this supply can output ?
^
^
Not sure how to measure for how many ma it puts out. :-[
I was thinking that it should be possible to double the ma output by dupilcating the IRF740, snubber, inductor, diode and reservoir cap. ie two parallel SMPS running from the same 555. Obviously the current draw would be significantly higher, but using each of the parallel outputs to drive one dual triode (in a two dual triode design) should give significantly higher voltages and increased performance before saturation of the inductors occurs.
Neat design, but I do wonder why you've connected the negative grid biasing circuit to the gate of the mosfet. As long as there is virtually no load on the negative rail you will be fine else it will reduce the efficiency of the mosfet because the gate isn't driven hard enough. Wouldn't it be better to connect the negative charge pump to the drain of the mosfet?
Quote from: frequencycentral on November 07, 2009, 04:52:33 AM
^
^
Not sure how to measure for how many ma it puts out. :-[
I was thinking that it should be possible to double the ma output by dupilcating the IRF740, snubber, inductor, diode and reservoir cap. ie two parallel SMPS running from the same 555. Obviously the current draw would be significantly higher, but using each of the parallel outputs to drive one dual triode (in a two dual triode design) should give significantly higher voltages and increased performance before saturation of the inductors occurs.
You would have to sync the two oscillators to prevent beat frequencies from occurring. Just being 30 Hz off is enough to give you audible noise..
Also, I'm not sure how well a direct duty cycle supply will handle being paralleled. Current mode supplies are good at this because both can sense when the load has changed and will adjust accordingly. Direct duty cycle control OTOH just knows that more current = more duty cycle. One of the supplies may be able to try to pull too much current and fail. It may not be a problem with what you're trying to do but it's something to be aware of with simple switchers like these.
Quote from: g. on November 05, 2009, 05:24:24 AM
thanks for sharing !
i'm curious,
how many mA this supply can output ?
Nixie PS max. 10ma
just for one or two 12a*7
i found this one : here http://www.unitechelectronics.com/NE-555.htm (http://www.unitechelectronics.com/NE-555.htm)
(http://www.unitechelectronics.com/NE-555-FIGURE24A.gif)
QuoteA simple circuit to power a NEON lamp. Primarily used to test neons where safety is a requirement.
The R1 - R2 - C1 circuit determines the NE-555 to oscillate producing a voltage at Pin 3 driving
the small 8 ohm transformer's primary windings, the secondary windings are 1K ohms. It works.
This results in a ratio of 125 times gain, however we all know that's not going to fly. Losses ??
The theoretical voltage of 500 Volts AC passing through R3 10K dropping to around 180V AC
thus striking the gas within the neon and lighting it. This circuit was designed for pocket use.
Is it possible to obtain like 400-422v with this system? I would use it to build a tube dual rectifier preamp - 4 12AX7s.
i don't think so...
best is to use the EH toroidal transformer
Quote from: manis404 on November 12, 2009, 12:42:47 PM
Is it possible to obtain like 400-422v with this system? I would use it to build a tube dual rectifier preamp - 4 12AX7s.
Depends greatly on the load. I saw a circuit very similar to this one produce greater than 1kV (measured with an electric field meter), but then the 10Mohm input of a digital multimeter dropped it down to something like 300V.
Hi pals!
I'm following this thread a time ago because i'm interested in building a tube miniamp for bedroom practice.. but something hangs me out. I don't fully understand which is the amperage rating of this or other nixie supply units... Let's say if I power the whole thing from 1A 220 / 12v transformer, it would deliver 1A or it will shrink to the 10ma rating posted pages ago?. Could I use this nixie smps to power a SE tube power amp?
Hope you can help me
Sebastian.-
why not only use a 12v/2A transformer and connect it to a normal recticifier (for filaments) and to a voltage multiplier circuit? you can easly power a small amp from it without problems, and it won't take much space if you know how to project a pcb.
Yes! After watching carefully this proyect (http://www.jjs.at/electronic/class_a_subminiature.html) I found out that I could feed the heathers by other means than using precious mA from the SMPS. thanks for the answer!
Quote from: juancra on November 14, 2009, 10:15:52 PM
Hi pals!
I'm following this thread a time ago because i'm interested in building a tube miniamp for bedroom practice.. but something hangs me out. I don't fully understand which is the amperage rating of this or other nixie supply units... Let's say if I power the whole thing from 1A 220 / 12v transformer, it would deliver 1A or it will shrink to the 10ma rating posted pages ago?. Could I use this nixie smps to power a SE tube power amp?
Hope you can help me
Sebastian.-
You cant get more power out of your wall wart then you put into it.... A 12V 1A transformer can supply 12 watts of power.
Multiply voltage by current to get power. At an ideal 100% efficiency voltage conversion, you should be able to get any voltage + current rating that when multiplied together equal 12 watts.... So You could get 48 volts, 250mA, 6V 2A,120V 100mA...
So you see, at high voltages you get very little current but it's still the same power. Of course, nothing is 100% efficient at power conversion, so you lose a decent amount of available watts in the process.
If you are making a tube amp with this you are limited by the amount of current the wall wart can supply, the amperage + voltage rating of your switching power supply.
I believe it was said 300V 100ma, so multipy those two together and you get 30 Watts. That doesnt mean you can make a 30 watt amplifier out of it, though... amplifiers use up current in many more ways than just straight out the speaker (especially tube, with their filaments) If you want the full available output power, then you would need your 12v wall wart to be... 30 watts / 12V = 2.5A. 12V 2.5A Wall wart.
EDIT: Oops, it was 10ma. Thats 300V x 0.01A = 3Watts. Not enough to power a decent tube amplifier unless it is like a <1Watt... sorry. You need to do your homework on your amp and calculate an estimate for power waste + speaker out, decide on your minimum power supply specs - and then find something above those (you don't want your amp barely getting by, you want some margin of safety)
Yeah.. I don't think that this is viable for an all tube amp... All of this came by because I found, on a local store, an amount of nos tubes and wanted to build a cheap test bed to run tests on them.. but think I'll buy a commercial power trans instead =)
Thanks for the info!
I successfully built the 555 smps - I used the verified layout from Rick, then I tried to do a Vero version too...
Ended up to be a close copy of the perf one...Should work!
(http://www.aronnelson.com/gallery/main.php?g2_view=core.DownloadItem&g2_itemId=42214&g2_serialNumber=1)
And does the vero layout work? I´m waiting for deliveries of the mosfets and want to make one too !
IT IS VERIFIED!
Cool ! :) I'll make one next week and report back. Ciao
Hi Renegadrian
The parts came, I used your layout and it works : from 120 V to 270 V (without load) !
Have anyone allready used this power supply in a pedal, I´m thinking of the Real McTube .
Ciao
Glad it worked out fine - I told ya!!! :icon_wink:
As promised, I made the real McTube with Renegadrian´s layouted power supply. A perfect couple !
yes! pics please!!!
Hi Renegadrian,
When I come home this evening I'll send you some pictures. Don't expect too much though, I built the Real McTube on a (real) piece of breadboard.
It's really cool that I can dial in the voltage as given in the schematic. Yeah that SMPS is really flexible. The SMPS doesn't get hot, not even warm after 2 hours.
I did some listening at low levels : through my Laney VC30 and (in my workplace) a Vox plugg-in. Fuzzy distortion with a tube-depth. Again at low level.
I tried it with 2 valves an old China ECC83 and a Sovtek ECC83 WA. The difference was noticable, so further testing and listening ahead !
I made a vero for the MAX1771 Charge Pump, i've spaced it out a bit more as I think it might be a bit more sensitive to stray capacitance than others on vero... (or is the opposite right and I shoulda made it smaller... will probably make a smaller one later anyway) only one way to find out though! Unverified as of yet.
(http://i898.photobucket.com/albums/ac182/Scruffie_Crow/MAX1771SMPS.gif?t=1277109529)
(All thanks go to Rick Holt & Nick The Designer)
Here's (as promised) a picture of my preliminary build Real McTube. Fully functional, waiting for a box.
(http://i47.tinypic.com/mtxqgj.jpg)
With the MAX1771 smps you may want to use high amperage rated inductors such as these from Rapid: http://www.rapidonline.com/Electronic-Components/Inductors-And-Chokes/Leaded-Inductors/High-current-leaded-suppression-chokes/79278/kw/
Also worth uprating the reservoir caps voltage capability if you plan to tweak the smps in anyway - I was getting 500v out of mine at one point. Banzai sell some quite small 350v 4.7uF caps: http://www.banzaimusic.com/Roederstein-EKA-4-7uF-350V.html
You can tweak up the maximum available voltage by screwing around with the trimmer and it's two resistors, I ended up using 180k/1k trimmer/1k instead of 1M/5k trimmer/10k.
Good luck with building onto veroboard - that's a lot of copper strips to act as aeriels. In the MAX1771 thread Nick Desmith posted:
Quote from: nickds1 on April 12, 2010, 09:59:37 AM
You are actually quite lucky it worked on a proto board - MAX1771s are pretty sensitive to stray capacitance and you may have a few unexpected high frequency artifacts in there
I found the 1771 smps to work on breadboard but was highly unstable. On perf it works very well IMO. Better still would be a PCB with large ground plane. Nick Desmith on his PCB layout:
QuoteYou can see the shadow of the ground plane on the underside and note that several vias in parallel have been used to connect Rsense to the ground plane - each via can typically handle a few 100 mA, and as up to 2A can flow through Rsense we need to provide a good low impedance path to ground.
translated from HERE (http://www.cavva.hiponet.it/index.php?option=com_content&view=article&id=40:alimentatore-step-up-per-nixie&catid=2:articoli&Itemid=4)
A power supply to feed nixie tubes and PIC. It goes at 12V and it will charge up to 180V.
max current is 11mA. this schem uses the MAX771.
resistors must be 1/4W 1%. The mosfet doesn't get hot so heatsink is not needed.
220uH must be max 100mA.
(obviously the PIC part is not needed for our circuits, so it can be deleted)
http://www.cavva.hiponet.it/schemi%20elettronici/alimentatore%20nixie.jpg (http://www.cavva.hiponet.it/schemi%20elettronici/alimentatore%20nixie.jpg)
http://www.electricstuff.co.uk/nixpsu.html (http://www.electricstuff.co.uk/nixpsu.html)
http://www.desmith.net/NMdS/Electronics/NixiePSU.html
I read the articles on the use of the MAX1771 in an SMPS . Seems like a good idea to make a SMPS that I could use for a HOTBOX ...
However it's an expensive chip compared to the NE555 I'm currently using in my SMPS. On top of that : the availability in Europe is low.
Reading through this article http://www.desmith.net/NMdS/Electronics/NixiePSU.html I saw that the writer also mentions the following chip : MC34063 as a possibility to use in his SMPS .
I found the MC34063 (complete MC34063ACN, producer ST Microelectronics ) at the RS internet store under stock NR 355-2706 for 0,82 €/pce. Moreover it's in stock !
Has anybody tried this? Or should we try it ?..
I'll buy new glasses...I swear...
RS stock item NR 516-5095 made by ON Semiconductor part NR MC34063AP1G : 0,51 €/pce !
I believe that's the one specified !
Question as in previous message.
PS I'm in no way affiliated with RS, their website was handy
Quote from: Renegadrian on February 07, 2009, 10:44:28 AM
I'd like to make a new topic, did a quick search but there is not a similar one...
So I think it's quite useful to have all the voltage multipliers posted here...
As I wrote in the Valvy topic, here --> http://www.diystompboxes.com/smfforum/index.php?topic=63479.msg597319#msg597319
I wanted to try this circuit here --> http://w1.859.telia.com/~u85920178/power/vconv_01.htm
with 4 trannies and a low number of caps and diodes...
It works, altough I didn't put this circuit in a tube pedal like the valvy yet, I built it successfully, now I got 49.8V from the 14V I got from my unregulated wall wart - did I tell you I finally got a DMM?! ;D
I believe it will find a good use in a tube project!!!
Here it is, mine has just a stage less to get that 48V
(http://w1.859.telia.com/~u85920178/power/vconv_comp.gif)
the link seems to have gone 404, but here is the layout...
(http://img682.imageshack.us/img682/2861/vconv48layout.gif)
and the one I made...Yellow lines are on the top side.
(http://img697.imageshack.us/img697/1779/vconv48.gif)
By the way, harry's page has moved, but it is still available, I just found it:
SM0VPO's page, voltage converter (http://www.sm0vpo.com/power/vconv_01.htm) has a bit more info on the circuit.
So if I am understanding the logic of a voltage multiplier correctly,
1. For each voltage doubling stage, there is a halving of current.
2. The maximum input voltage from the wall wart is 12v. Is this the wart's peak output, or RMS output?
Thank you.
Hi,
does anybody has vero layout for the SM0VPO circuit ? Renegadrian maybe ? I've looked into your Aaron's gallery section, but didn't find it.
Thanks
Ciao
No vero on that one, the perf is quite easy and I did it that way...Ciao a te!!! :icon_wink:
Hi,
i'm experimenting with some of your voltage multipliers schematics; i have a question: it is possibile to obtain 'only' 50V with the nixie psu thing (the one with the 555 inside) ? As these are my first tries with simil HV, i'm a little bit scared to go and jump onto the 100V and more train....
Also, i've tried to feed my valvecaster with the pconv voltage multiplier (the renegadrian's one with BC557 and 547); i am using a 7812 for the tube, and i pick 18V at first couple of diodes, send it to the 7812 for the tube and then pick the 48V (last diodes stage) and send it to the tube anode... But... i am getting a lot of noise... is it regulare to pick two different voltages from that kind of circuit ?
Thanks !!!
Have a nice time
Quote
i'm experimenting with some of your voltage multipliers schematics; i have a question: it is possibile to obtain 'only' 50V with the nixie psu thing (the one with the 555 inside) ? As these are my first tries with simil HV, i'm a little bit scared to go and jump onto the 100V and more train....
I read that the minimum voltage should be 100v more or less, up to 200 when maxed. I'd say go for it, it requires little precautions after all...
Quote
Also, i've tried to feed my valvecaster with the pconv voltage multiplier (the renegadrian's one with BC557 and 547); i am using a 7812 for the tube, and i pick 18V at first couple of diodes, send it to the 7812 for the tube and then pick the 48V (last diodes stage) and send it to the tube anode... But... i am getting a lot of noise... is it regulare to pick two different voltages from that kind of circuit ?
I think it should work with two exits, but I never tried myself...sorry I cannot be more helpful on that one...did you try to filter it somehow?!
'Nother charge pump for the collection. I believe this one is more efficient (~70%) that the MAX and 555 circuits, but the output is unregulated so the output resistance is around 6k. However, even when charged up to 80V you can touch the output and feel nothing, so it appears to be shock-less! Switches at about 300kHz.
(http://i81.photobucket.com/albums/j207/merlinblencowe/DM160/MiniInverter.jpg)
That's awesome. :icon_cool:
Quote from: merlinb on October 05, 2010, 05:20:27 AM
'Nother charge pump for the collection. I believe this one is more efficient (~70%) that the MAX and 555 circuits, but the output is unregulated so the output resistance is around 6k. However, even when charged up to 80V you can touch the output and feel nothing, so it appears to be shock-less! Switches at about 300kHz.
(http://i81.photobucket.com/albums/j207/merlinblencowe/DM160/MiniInverter.jpg)
To me, shockless means no current and a crappy supply :P. I liked the little HV SMPS's with adjustable voltage rails. At about 120V you get a little tingle. At about 250V, it's more like an angry ant bite :icon_lol:.
Quote from: Cliff Schecht on October 07, 2010, 02:08:49 AM
To me, shockless means no current and a crappy supply :P. I liked the little HV SMPS's with adjustable voltage rails.
Thanks for the technical appraisal. (Still trying to find "crappy" in my scientific dictionary...)
adj. crappy: Vulgar Slang
1. Accessible to those who have only previously dealt with 9 volts.
2. Safe.
3. Do-able.
:icon_lol:
The little tube amp I'm working on for PAiA runs on only 170V DC after FW rectifier but would still probably give you quite a zap. Haven't actually tried to get shocked by that amp though..
(http://dl.dropbox.com/u/967492/Slim%20PCB.gif)
(http://dl.dropbox.com/u/967492/Slim%20PnP.gif)
Hey guys a quick update on my SMPS build, just finised a nixi smps with 555 (well i used a 556 bc i didn't have a 555... imagine that). The only thing i've changed is: inductor - 220uH and output cap filtering cap is 4.7uF/450v. I've managed to sqeez 300v with 100k/1w load. My fet is running cold so every thing seems to be in place (it's running for about 3 hours). Thank you guys for sharing the schematic ;)
Best regards,
Gabriel Tudoran
Analog Sound
Hey guys a new schematic for a SMPS (i don't know if it's already posted). 270-300V @ output with 100mV ripple, it runs @ ~100kHz and you can put out max. 10mA (you can make some math yourself if you like other values - just look at the datasheet and you have all the formulas for this IC).
(http://dl.dropbox.com/u/15275178/Pictures/SMPS-2.JPG)
Best regards,
Gabriel Tudoran
Analog Sound
LE: The Ipk=544 mA so use a Inductor and a Diode that will handle at least 10% over this value.
this one is pretty impressive !
120V from 12v ac !!!
(http://www.sugardas.lt/~igoramps/tomato_preamp.jpg)
http://www.sugardas.lt/~igoramps/tomato_preamp.htm (http://www.sugardas.lt/~igoramps/tomato_preamp.htm)
Yeah it is easier if you have 12V AC - you can use the C0CKROFT WALTON and get very high voltages with just a bunch of regular components! this one seems smart too! I guess I have to buy a 12V AC wall wart!
Or can I hack a DC one and get rid of the rect. bridge!? I guess there's AC just before it, am I right?!
Quote from: Renegadrian on January 31, 2011, 08:20:54 AM
Or can I hack a DC one and get rid of the rect. bridge!? I guess there's AC just before it, am I right?!
yes !
40106 is another cheap IC that can be used to multiply voltage - here is a VERO LAYOUT (http://www.aronnelson.com/gallery/main.php/v/Renegadrian/40106+voltage+multiplier.gif.html) I made - verified, it works so good with a valvy!!! :icon_cool:
Quote from: Renegadrian on February 02, 2011, 07:04:24 PM
40106 is another cheap IC that can be used to multiply voltage - here is a VERO LAYOUT (http://www.aronnelson.com/gallery/main.php/v/Renegadrian/40106+voltage+multiplier.gif.html) I made - verified, it works so good with a valvy!!! :icon_cool:
Hi can you point me the schem of this one ?
(http://thumbnails37.imagebam.com/11791/758432117905684.gif) (http://www.imagebam.com/image/758432117905684)
Thanks !
only small caps with this one, can be a really small B+ provider, i 've some 40106, will test it shortly, and 2,5 mA are enough for some circuits
My lil' NIXE SMSP with a redesigned pcb and some Oscope shoots with DC ripple (the load was 4 triodes).
(http://dl.dropbox.com/u/15275178/Pictures/CIMG1867.JPG)
(http://dl.dropbox.com/u/15275178/Pictures/CIMG1876.JPG)
(http://dl.dropbox.com/u/15275178/Pictures/ripple.JPG)
Best regards,
Gabriel Tudoran
Analog Sound
I was wondering, at what voltage does the 12AU7 begin to go from "starved plate" to non-starved plate. I want to make a supply, but I was wondering if there is a low voltage that works, or does the sound change linearly with an increase in voltage? I know all tubes are different, but I have a number of multipliers with 80V as the B+ voltage. What voltage do tube amps use? Do they use the maximum voltage?
thanks,
Curious Geroge
Voltages running inside an amp are usually between 250 and 350. Usually anodes of a standard double triode get 250-280 if memory serves well...
yeah thats about right as far as I know. depends on what amp too. 240 is a good ball park for 12ax7 it seems. You can go down to 125 or lower and still get good sound though. Less voltage causes more clipping which is good in our case. the tone suffers at low voltage and the clipping is fizzy and doesnt sustain as well as it could in my opinion. 80 volts could be very cool though. Cascading two tubes together at 80v would make a heck of a overdrive :icon_mrgreen:
Quote from: BarnyardBill on February 08, 2011, 01:25:01 PM
I was wondering, at what voltage does the 12AU7 begin to go from "starved plate" to non-starved plate.
There's no exact point. As you say, there is a gradual change. However, in working with cascodes I have observed that most preamp valves show a more rapid increase in gm when you get to... you guessed it, 80V! For this reason I assume 80V to be the 'transistion zone', at least for the ECC81/2/3.
thanks for all the help, I think I'm ready to order some parts for the multiplier now. I didn't realize how much I have gotten used to the valvey until I switched it off. Since I only have a solid state Peavy Amp, the valvecaster really shines through. I might make one and just set in on top of my amp since I leave it on all the time anyway.
-Bill
I wanna yank the step-up transformer out of my supply (it only steps up to 104V). I was wondering, can I sub a IRF730 for the 740? It's 5.5A, 400V, 1Ohm on resistance, where the 740 is showing 10A, 400V, 0.5Ohm. It's mainly the voltage handling we're after, correct? Does 1/2 ohm on-resistance matter much in these multipliers? And, I assume even the 5.5A rating is still way over-safe for these. I have a couple 730's I don't have anything else to do with, and they both have neat little heat sink clip-ons.
Quote from: Earthscum on February 19, 2011, 02:41:06 AM
I wanna yank the step-up transformer out of my supply (it only steps up to 104V). I was wondering, can I sub a IRF730 for the 740? It's 5.5A, 400V, 1Ohm on resistance, where the 740 is showing 10A, 400V, 0.5Ohm. It's mainly the voltage handling we're after, correct? Does 1/2 ohm on-resistance matter much in these multipliers? And, I assume even the 5.5A rating is still way over-safe for these. I have a couple 730's I don't have anything else to do with, and they both have neat little heat sink clip-ons.
You can use 730 but you may find that it will be a little more hot (less resistance = less voltage drop across channel => less power to dissipate). You wanna do a flyback SMPS? if so you will need a Xformer that will support the switching freq. (a ferrite core wich will go up to 30-40kHz). But if you don't wanna do a flyback why do you wanna complicate things with xformers... use a small inductor and that shoud be it.
Best regards,
Gabriel Tudoran
Analog Sound
Hi all,
i just recently try to build the nixie supply, after a smoke test, i get HV output definitely, but the IRF740 gets very HOT!.
Here's the different thing i had on my build:
a. 100uH using FT37-43 toroid 17 turn, according to its spec, it would make 100uH.
b. UF4004 replaced by UF4007
c. 2.2uF output cap, replace with 10uF 400V cap
i suspect using FT37-43 100uH coil and 10uF 400V is BAD, will get the correct parts as soon as i have time to go to the local store :). and BTW, i use 12V input supply.
here's a photo of my build, i would really appreciate if you guys could help. thank you.
(http://i266.photobucket.com/albums/ii280/iyung_w/mix/IMG_0019.jpg)
Yeah, I think your inductor is the problem. The 10uF reservoir cap should be fine, better even, although with this type of supply it's easy to exceed the maximum rating of the cap (and smoke it) if you're not careful. I always use a small heatsink on the MOSFET, with a little thermal gel for heat dissipation.
Do NOT ever ever ever use a thoroid inductor in this kind of PS! Use either a ferrite bar or a standard inductor (experiment with values from 60 to 150uH and you will find a point where the ballance is right), the variable voltage output is made by varying the Frq. and not the DC (and this is a lil' bit tricky), you can also change the 2n2 oscilator cap to 1.2-1.8 nF. and if you feel that you need a smaller PS i can give you the SMD version.
Best regards,
Gabriel Tudoran
Analog Sound
Quote from: frequencycentral on March 27, 2011, 06:57:42 AM
Yeah, I think your inductor is the problem. The 10uF reservoir cap should be fine, better even, although with this type of supply it's easy to exceed the maximum rating of the cap (and smoke it) if you're not careful. I always use a small heatsink on the MOSFET, with a little thermal gel for heat dissipation.
Quote from: gtudoran on March 27, 2011, 07:04:56 AM
Do NOT ever ever ever use a thoroid inductor in this kind of PS! Use either a ferrite bar or a standard inductor (experiment with values from 60 to 150uH and you will find a point where the ballance is right), the variable voltage output is made by varying the Frq. and not the DC (and this is a lil' bit tricky), you can also change the 2n2 oscilator cap to 1.2-1.8 nF. and if you feel that you need a smaller PS i can give you the SMD version.
Best regards,
Gabriel Tudoran
Analog Sound
thanks for the answer, i plan to put a small heatsink to the mosfet. also, i do have a couple of ferrite bar, kind of a tubular shape, 4mm diameter, 15mm length, but i do not know how to calculate the value needed. i'll experiment later on this one.
thanks again.
julius
ok, i got my ps working very well just by replacing the inductor. IRF740 definitely cool down.
is there any way to pump the output voltage within 200-300V range? i am trying to build P1 amp from AX84, its a 2x12AX7 and a EL84. would this PS provide enough current?
thx.
Hey casiomax,
You can't supply an output stage tube with this SMPS - don't think that this PSU will supply enough current for a EL84 outputstage. As far as the voltage output goes i was able to sqeez 280v from it (275v with load) - i've changed the oscillation capacitor with 1.5nF as fara as i remember, all the other parts are the same, i also recomand you tu use pcb and a ground plane for this PSU.
Best regards,
Gabriel Tudoran
Analog Sound
Quote from: casiomax on March 29, 2011, 05:35:09 AM
ok, i got my ps working very well just by replacing the inductor. IRF740 definitely cool down.
is there any way to pump the output voltage within 200-300V range? i am trying to build P1 amp from AX84, its a 2x12AX7 and a EL84. would this PS provide enough current?
thx.
Hi Gabriel,
again, thx for the input. I know not much about SMPS, but i understand a bit now, changing the oscilator cap means changing the frequency in result different desired output voltage, like you have mentioned before.
I read the EL84 datasheet, if i am not mistaken it requires more than 60mA to operate, as for 12AX7, it only requires less than 5mA, this means firefly project will be able to use SMPS. cmiiw.
Quote from: gtudoran on March 29, 2011, 07:48:39 AM
Hey casiomax,
You can't supply an output stage tube with this SMPS - don't think that this PSU will supply enough current for a EL84 outputstage. As far as the voltage output goes i was able to sqeez 280v from it (275v with load) - i've changed the oscillation capacitor with 1.5nF as fara as i remember, all the other parts are the same, i also recomand you tu use pcb and a ground plane for this PSU.
Best regards,
Gabriel Tudoran
Analog Sound
hey casio, you can fire up a 6k6gt at 250 volts ( lower if you want = less watts ) They pull around 37 ma and put out around 3.4 watts. a 2 x 12ax7 preamp would make a pretty wicked amp.
I used a 1363 smps to make one awhile ago. only one 12au7 preamp tube though. http://www.youtube.com/watch?v=pAc2FTzLwbk . i dont really have a schematic but it was pretty basic. look up the power tube on duncan amps sight. you could just use the p1 schematic too. Good luck. send me a pm if you need anymore info. i dont check in enough on here anymore. Greg
Casiomax that is correct but in a preamp stage you will not be even close to 5mA (with nixie modifid smps i've managed to suppy 4 x 12Ax7 without any problems) so if you would like to make a small wattage amp with a 12au7 in PP configuration i guess that could work ... but a El84 i rilly doubt about it. If i can help you with smth or need other comments regarding this PM me or use my mesenger ID.
Best regards,
Gabriel Tudoran
Analog Sound
Quote from: casiomax on March 29, 2011, 07:55:16 PM
Hi Gabriel,
again, thx for the input. I know not much about SMPS, but i understand a bit now, changing the oscilator cap means changing the frequency in result different desired output voltage, like you have mentioned before.
I read the EL84 datasheet, if i am not mistaken it requires more than 60mA to operate, as for 12AX7, it only requires less than 5mA, this means firefly project will be able to use SMPS. cmiiw.
Quote from: gtudoran on March 29, 2011, 07:48:39 AM
Hey casiomax,
You can't supply an output stage tube with this SMPS - don't think that this PSU will supply enough current for a EL84 outputstage. As far as the voltage output goes i was able to sqeez 280v from it (275v with load) - i've changed the oscillation capacitor with 1.5nF as fara as i remember, all the other parts are the same, i also recomand you tu use pcb and a ground plane for this PSU.
Best regards,
Gabriel Tudoran
Analog Sound
Hi Guys,
Finally got round to building the nixie supply that rick has posted on this thread!:)
Works a treat upto 250v but i would like to get 300v if possible!
The supply outputs 310v's but if i connect it too 2 12ax7's i get a pulsing noise almost tremelo like, think its moataboating!
The nixie is being supplied by a 12v 2amp powerpack and the parts are exactly as rick has, same inductor and all:(
Can the nixie supply enough current to power 2 12ax7's at 300v's?
any thoughts, or suggestions on alternative power supplies?:)
cheers
craig
At these voltages you might consider conventional tube amp power arrangements. with four triode stages you've got two sets of two in phase with each other. You'll probabaly combat the motorboating by using a resistor (and a HV cap to ground) to drop the HV slightly for the first and second stage with respect to the third and fourth. That way, stages in phase with each other are seeing different voltages - B1 and B2 respectively.
Cheers rick, that is one speedy reply!I Assume your tinkering tonight to then:)
So Your saying instead of supplying the two stages direct from the nixie, Split the supply using a resistor to get a B1 and a B2. say a 1k resistor to both feeds?
/------ 1k ----- B1
/
Nixie----
/
/------ 1k ----- B2
Could you output a high frequency from a CMOS oscillator into, a real transformer to get 230V in your pedal without the need for a mains connection inside it?
Like this:
(http://dl.dropbox.com/u/967492/B%2B%20B1.JPG)
That should drop you enough voltage (10 or 20 volts). Play with the values. If this were a tube amp you'd have maybe a B2 too, another resistor and cap to get a lower voltage still. Worth looking at a few tube amp schematics to get the idea. Also consider grid stoppers. And maybe adjusting the gain structure by tweaking the cathode resistors upwards slightly.
Thanks rick ill give it a whirl and see what happens:)
hey guys,
Finally got round to trying ricks suggested ideas! Seems to have helped a bit, not getting squealing but still getting the pulsating effect???
If i play guitar the pulse is only audible if i not playing, its louder if i drag my hand across the strings? It only happens when the gain is turned up?:(
Sounds mean at low gain settings but want the full range.
The effect i have combined the power supply with is the soldano supercharger gto:
http://hayashimasaki.net/WP2/wp-content/uploads/2010/10/superchargerschematic.jpg
I cant see anything up with the schematic, and have built it on turret board!?
Any further ideas would be a great help?
I am guessing from what i read you have the ps going nixie>>cap to ground>>>>resistor>>>>>cap to ground right? try bigger reservoir caps like in a tube amp. I am using the 1363 smps and running two power tubes ( 12au7) and a preamp tune all off of one smps at 200 ish volts. Its arranged like I wrote above. capa are 22uf 400v and resistor is 100ohm so i dont drop to much voltage. No squeels etc. it was motorboating a little and scrackling before i did the ps like this though. Hope that helps it..good luck and post results of the gto!!! I want to hear that thing!
hey cheers for the fast reply:)
Just before you posted i thought id try a bigger resistor to split the two B+'s worked a treat, 10k minimised it a bit more and 22k has removed it completly!:)
Think some where in the middle might be ideal but only got 22k's at the mo!!
It is a pretty badass distortion!! very soldano:) I like!!
Only issue i have now is that it squeals when nothing is plugged into the input!? Do i need to somehow ground the input when not plugged in, to be fair this isnt on a 3pdt switch yet so that might resolve the issue anyways with a grounded input layout??
im not sure but i think that would squelch it. High gain makes things squeal a lot. Got sound clips of that beast? I am more than curiouse :icon_wink:
after looking at the schematic, the relay switch does ground the circuit when its bypassed. Dont know if it cures the squeal but they did do that. pin 6 on the relay i believe.
Quote from: Renegadrian on January 30, 2010, 09:29:01 PM
I successfully built the 555 smps - I used the verified layout from Rick, then I tried to do a Vero version too...
Ended up to be a close copy of the perf one...Should work!
(http://www.aronnelson.com/gallery/main.php?g2_view=core.DownloadItem&g2_itemId=42214&g2_serialNumber=1)
I'm just putting one of these together. I noticed the R6(2k2)/C2(100pF) should be on the other side of the diode as in the original schematic and Rick's perf layout.
Here's a vero layout I knocked up and am starting to build. Based on this schematic posted by Frequency Central and Renegadrian's vero.
(http://dl.dropbox.com/u/15632336/lektronix/Misc/555%20SMPS/555%20SMPS%20stripboard.gif)(http://dl.dropbox.com/u/15632336/lektronix/Misc/555%20SMPS/NixieSMPS.jpg)
I had a piece of stripboard this size so made the layout to fit. The gaps between tracks are really thin on the stuff i've got hence the cut across row b. The jumper from e9 to f10 is on the solder side of the board.
Building now so will verify when done.
edit
*Layout about is Verified working*
Quote from: Renegadrian on July 20, 2010, 09:23:50 AM
Quote from: Renegadrian on February 07, 2009, 10:44:28 AM
I'd like to make a new topic, did a quick search but there is not a similar one...
So I think it's quite useful to have all the voltage multipliers posted here...
As I wrote in the Valvy topic, here --> http://www.diystompboxes.com/smfforum/index.php?topic=63479.msg597319#msg597319
I wanted to try this circuit here --> http://w1.859.telia.com/~u85920178/power/vconv_01.htm
with 4 trannies and a low number of caps and diodes...
It works, altough I didn't put this circuit in a tube pedal like the valvy yet, I built it successfully, now I got 49.8V from the 14V I got from my unregulated wall wart - did I tell you I finally got a DMM?! ;D
I believe it will find a good use in a tube project!!!
Here it is, mine has just a stage less to get that 48V
and the one I made...Yellow lines are on the top side.
(http://img697.imageshack.us/img697/1779/vconv48.gif)
Here's a vero for the circuit above. Not yet verified but looks good and will be building this later.
Repeat the last stage for more voltage, I only need 48v.
(http://dl.dropbox.com/u/15632336/lektronix/Misc/Voltage%20Converter/Voltage%20Converter%20stripboard.gif)
Quote from: sundgist on June 25, 2011, 03:17:57 PM
Quote from: Renegadrian on January 30, 2010, 09:29:01 PM
I successfully built the 555 smps - I used the verified layout from Rick, then I tried to do a Vero version too...
I'm just putting one of these together. I noticed the R6(2k2)/C2(100pF) should be on the other side of the diode as in the original schematic and Rick's perf layout.
As you can read here http://www.diystompboxes.com/smfforum/index.php?topic=74088.msg661738#msg661738 Rick made his first version like mine, then corrected it and reuploaded it - guess it doesn't change much, it's just a resistor and a cap to ground. I built mine that way and some other people too and got it working flawlessly, so I just left them that way...
On the other layout, c4-6-8 are 220µ on the original plan.
You know something I just though of trying? Make a self-oscillatiing relay feeding a small transformer (6v+6v) with a center tap in the secondary...
The relay must be a DPDT, so we could use one side of the switch to make the oscillator and the other side to feed the secondary of the transformer. Might be something to try out if you want a REAL portable tube-amp... maybe use one of those 12v/7A sealed batteries...?
Oscillator
(relay's coil)
__________o o___X A ____o o___ B A ______ __________
( | \ \ )||(
( | + \ - - - - - - - - - - - - - - - - - - - - \ )||( High Voltage
( === \ \ ________________)||(
( | | | | )||( Output
(____| o o | )||(
| V+ V+ | B ______)||(_________
___|___ ___|___
Quote from: blackcorvo on June 27, 2011, 04:26:40 AM
You know something I just though of trying? Make a self-oscillatiing relay feeding a small transformer (6v+6v) with a center tap in the secondary...
The relay must be a DPDT, so we could use one side of the switch to make the oscillator and the other side to feed the secondary of the transformer. Might be something to try out if you want a REAL portable tube-amp... maybe use one of those 12v/7A sealed batteries...?
Oscillator
(relay's coil)
__________o o___X A ____o o___ B A ______ __________
( | \ \ )||(
( | + \ - - - - - - - - - - - - - - - - - - - - \ )||( High Voltage
( === \ \ ________________)||(
( | | | | )||( Output
(____| o o | )||(
| V+ V+ | B ______)||(_________
___|___ ___|___
You have just reinvented the vibrator power supply that was a feature of car radios until the age of the 12-volt plate tubes and 2N176 germanium power transistor.
Quote from: amptramp on June 27, 2011, 09:24:58 AM
You have just reinvented the vibrator power supply that was a feature of car radios until the age of the 12-volt plate tubes and 2N176 germanium power transistor.
Wow,,, I've never heard of that :o
Quote from: Renegadrian on June 26, 2011, 09:24:51 PM
On the other layout, c4-6-8 are 220µ on the original plan.
Hmmm. You're right. I was following the schematic higher up on that page. The author mentions 2k2uF is plenty at 60v, but as you say the layout lower down shows 220uF.
Quote(http://dl.dropbox.com/u/15632336/lektronix/Misc/Voltage%20Converter/Schem.bmp)
The multiplier circuit shown (to the right) is repeated as many times as needed. It uses just two diodes and two electrolytic capacitors to make a copy of the input voltage and add it to the original voltage. In this way it will add 12v to give 24v. Build two multiplier stages and the voltage will rise to 36v. The PCBs in the ZIP file go all the way up to +60v. Since the output current capability reduces as the voltage rises, so too does the need for the 10uf capacitors. With 60v, only 2.2uf at 64v working is necessary. This will still fit on the PCB if you get the right component.
I'll try with 10uF as I've got a bag full and see how it performs.
Quote from: blackcorvo on June 27, 2011, 04:18:34 PM
Quote from: amptramp on June 27, 2011, 09:24:58 AM
You have just reinvented the vibrator power supply that was a feature of car radios until the age of the 12-volt plate tubes and 2N176 germanium power transistor.
Wow,,, I've never heard of that :o
Check out this schematic for a 1940 Buick radio showing a vibrator type power supply that chopped the 6-volt input and transformed it into a reasonabel B+ voltage:
http://www.nostalgiaair.org/PagesByModel/550/M0006550.pdf
There were other car radios that had synchronous vibrators that had a separate set of contacts that acted as the rectifier.
Quote from: amptramp on June 27, 2011, 09:57:36 PM
Check out this schematic for a 1940 Buick radio showing a vibrator type power supply that chopped the 6-volt input and transformed it into a reasonabel B+ voltage:
http://www.nostalgiaair.org/PagesByModel/550/M0006550.pdf
There were other car radios that had synchronous vibrators that had a separate set of contacts that acted as the rectifier.
Interesting...
I though of using this because I happen to have a 12v sealed battery, and I wanted to make myself a small portable tube amp, and the smaller, simpler and most efficient power inverter to use, the more "portable" this amp can be.
I'm also not aiming for too much power. Anything around 2w is enough (sometimes I get complains for playing the guitar even when its unplugged, and it is a common strat copy).
That's why im considering the idea of using a 6AS5 for my power tube, a 6BZ7 for the preamp, and maybe adding a solid-state drive channel, or just a semi-dirty booster to drive the 6BZ7.
I have yet to think a little more about it, because right now I'm working with another tube amp project that I want to make into a combo for home practice.
The portable one is more for the case of having a power outage, or travelling, or any situation a battery-powered amp might come in handy.
Quote from: blackcorvo on June 28, 2011, 07:18:09 PM
Quote from: amptramp on June 27, 2011, 09:57:36 PM
Check out this schematic for a 1940 Buick radio showing a vibrator type power supply that chopped the 6-volt input and transformed it into a reasonabel B+ voltage:
http://www.nostalgiaair.org/PagesByModel/550/M0006550.pdf
There were other car radios that had synchronous vibrators that had a separate set of contacts that acted as the rectifier.
Interesting...
I though of using this because I happen to have a 12v sealed battery, and I wanted to make myself a small portable tube amp, and the smaller, simpler and most efficient power inverter to use, the more "portable" this amp can be.
I'm also not aiming for too much power. Anything around 2w is enough (sometimes I get complains for playing the guitar even when its unplugged, and it is a common strat copy).
That's why im considering the idea of using a 6AS5 for my power tube, a 6BZ7 for the preamp, and maybe adding a solid-state drive channel, or just a semi-dirty booster to drive the 6BZ7.
I have yet to think a little more about it, because right now I'm working with another tube amp project that I want to make into a combo for home practice.
The portable one is more for the case of having a power outage, or travelling, or any situation a battery-powered amp might come in handy.
I posted a 24volt tube amp, its .4 watt, but even that is too loud sometime, my neighbors complain after 8pm from the other block.
http://www.diystompboxes.com/smfforum/index.php?topic=91606.0
no voltage multiplier needed.
Quote from: iccaros on June 28, 2011, 07:51:16 PM
I posted a 24volt tube amp, its .4 watt, but even that is too loud sometime, my neighbors complain after 8pm from the other block.
http://www.diystompboxes.com/smfforum/index.php?topic=91606.0
no voltage multiplier needed.
Cool, but I can't find these space charged tubes anywhere here in Brazil... and I can't buy anything via e-bay or any other site where I'll have to use paypal, because I don't have a bank account, so I wanted to try something easier for me to get. The idea I had for using the vibrator supply and the 6AS5 for the output are simple. The 6AS5 works at just 150v, it's a pretty cheap tube and not that hard to find. I might try using it at lower voltages, but I really wanted a portable amp that could give me some clean tones without having to lay my head on the speaker to hear it.
you can do that simply, I am building a small amp in to a snoopy lunch box with a 3 watt 6" speaker. you can take Ricks Superfly and exchange the 6111 with 12ax7 or 12au7's. The 12au7's work well at 120 volts.. and you can get a watt or more, which with an efficient speaker a 1 watt amp can be as loud as a 10 watt amp with inefficiency speakers.
I'm about to try out the 555 Nixie SMPS tomorrow and was wondering if breadboarding is advisable or not with high voltages like this. From what I can see from a bit of googling (and inferences from this thread) it should be relatively safe (at least, as safe as a circuit with such voltages can be). I just wanted to make sure I (probably) won't inadvertently blow up or fry something when I fire it up on the breadboard.
Also, in the Nixie SMPS pdf file, it recommends not using a battery as the 12v supply when doing the initial smoke test. I'm planning on using the SMPS with a 12v SLA battery to power a Superfly. I've got a radio shack adjustable power supply (the white kind with the reversable connector tip), would that be acceptable for the smoke test? I was also thinking about trying a 9v battery, since it can only supply so much current... I'd really hate to wind up with exploded battery guts all over me if at all possible, though.
So I breadboarded the Nixie supply today and it's not quite working. When I first attach the battery, the voltage shoots up to 80-90v, but immediately falls to around 4v, where it stays until I disconnect the battery. Then it slowly drops until it reaches zero or it's discharged. The guide mentions to check the 555 with a logic probe to make sure it's oscillating... I guess that means I'm off to find or build one to check that out. The inductor I'm using is a 100uH RF choke from radio shack; I built it from the schematic in the pdf file but using the components in rick's layout.
I checked the battery before and after testing it a few times; It was just over 10v before testing and about 9.75 afterwards, so it's not draining the battery too fast. Would I get better results using a wallwart power supply?
Quote from: jaapie on July 01, 2011, 05:54:10 PM
So I breadboarded the Nixie supply today and it's not quite working. When I first attach the battery, the voltage shoots up to 80-90v, but immediately falls to around 4v, where it stays until I disconnect the battery. Then it slowly drops until it reaches zero or it's discharged. The guide mentions to check the 555 with a logic probe to make sure it's oscillating... I guess that means I'm off to find or build one to check that out. The inductor I'm using is a 100uH RF choke from radio shack; I built it from the schematic in the pdf file but using the components in rick's layout.
I checked the battery before and after testing it a few times; It was just over 10v before testing and about 9.75 afterwards, so it's not draining the battery too fast. Would I get better results using a wallwart power supply?
In the next week I will attempt to build Ricks voltage multiplier so I will see if I can duplicate your issue and report back, I have the same inductor, just waiting on the transistors to start.
I rebuilt the circuit a few times and it still wasn't working right, so i built this little logic probe http://www.swansontec.com/sprobe.html (http://www.swansontec.com/sprobe.html) to check the output of the 555 (I used an LM358 for the opamp). When I check the output with the logic probe, only the "high" LED lights. I switched out the 2n2 cap to change the output to an audible frequency and not only could i hear the output when connected to a speaker, but both LEDs lit up (which is what I'd expect if it was oscillating). I changed the value back to 2n2 and tried a few different caps to make sure the one i'd been using wasnt bad, but every 2n2 I've tried won't light up both LEDs.
Since the circuit oscillates at lower frequencies with the exact same components (except for that cap), I'm pretty certain that the timer SHOULD be oscillating with the 2n2 caps-- but I have no way of telling (I don't have access to an oscope at the moment). The most reasonable explanations that I can think of are:
1. The timer IS oscillating, but with with the 2n2 cap, the output frequency is too fast for the LM358 to track, so it only lights the HIGH led
2. Maybe the breadboard's capacitance (or a bad/wrong value component) is screwing with that particular cap in such a way that lower values of caps (like the 2n2) are more affected than higher values
3. All my 2n2 caps are bad.
FWIW, All the caps I've tried so far are the little green mylar ones. Would electro or ceramic work better?
Also, since the problem appeared to be coming from the oscillator, I only have the 555 part of the SMPS on the breadboard right now (U1, R1, R2, R3, C1 and C2 on the schematic Rick posted on the first page)
Quote from: jaapie on July 05, 2011, 03:11:32 PM
1. The timer IS oscillating, but with with the 2n2 cap, the output frequency is too fast for the LM358 to track, so it only lights the HIGH led
Yeah, the whole point of a SMPS oscillator is for it to be operating above human hearing. Not sure of the freq of this one, but certainly higher than 20,000kHz. I doubt the LM384 (or your eyes if it did) would track that.
Also, I *think* it has an uneven pulse width duty cycle, so that would make sense that you're seeing only the 'greater' part of the pulse width - ie only lighting one LED.
Quote from: frequencycentral on July 05, 2011, 03:31:12 PM
Not sure of the freq of this one, but certainly higher than 20,000kHz.
Too many zeroes or extra k? :P
With my build, (I used 150uH inductor I had to hand) the frequency is about 45kHz from 230v down to 110v but then drops steadily to 18kHz as the voltage is turned down to 90v.
Can't help with where your issue might be, orientation/pinout of irf740 and bc547 perhaps?
Quote from: sundgist on July 05, 2011, 04:26:45 PM
Quote from: frequencycentral on July 05, 2011, 03:31:12 PM
Not sure of the freq of this one, but certainly higher than 20,000kHz.
Too many zeroes or extra k? :P
:icon_redface:
.....well, you knew what I meant. :D
I remembered that I've got a friend around the corner with a scope, so I dropped by to check out the oscillator output-- it IS oscillating after all. I guess I'd either built it wrong the first few tries, or my problem was somewhere else.
Quote from: frequencycentral on July 05, 2011, 03:31:12 PM
Yeah, the whole point of a SMPS oscillator is for it to be operating above human hearing. Not sure of the freq of this one, but certainly higher than 20,000kHz. I doubt the LM384 (or your eyes if it did) would track that.
Also, I *think* it has an uneven pulse width duty cycle, so that would make sense that you're seeing only the 'greater' part of the pulse width - ie only lighting one LED.
According to the math, the circuit should oscillate around 31kHz, which the scope verified.
So, back to the breadboard to see if I can get the rest of it working now. Thanks for the help!
QuoteAccording to the math, the circuit should oscillate around 31kHz, which the scope verified.
??? This just confused me for a bit so bear with me through this brain fart.
I've measured the ripple at the output which is 45kHz. Which is also mentioned in the notes here as the oscillator frequency. http://www.ledsales.com.au/kits/nixie_supply.pdf (http://www.ledsales.com.au/kits/nixie_supply.pdf)
My question is.... How does 31kHz become 45kHz??
I may now be making a few assumptions.
You've measured the output of the 555 at 31kHz which going by the values is right if the 555 is wired using only R3 (1k), R2
(10k) and C2 (2n2). Which I believe is how you measured 31kHz.
R1(56k) and bc547's collector on the control pin would be affecting this ratio to get it up to 45kHz, or in my case at 90v, down to 18kHz.
I havn't got a datasheet handy. Would this change the frequency or the duty %age?
Am I thinking this through right?
All replies appreciated though I am off to sleep right now......
QuoteI remembered that I've got a friend around the corner with a scope, so I dropped by to check out the oscillator output-- it IS oscillating after all. I guess I'd either built it wrong the first few tries, or my problem was somewhere else.
I suppose you could rebuild the whole circuit and take it back to your friend's and see what is happening.
Quote from: sundgist on July 05, 2011, 07:34:19 PM
I've measured the ripple at the output which is 45kHz. Which is also mentioned in the notes here as the oscillator frequency. http://www.ledsales.com.au/kits/nixie_supply.pdf (http://www.ledsales.com.au/kits/nixie_supply.pdf)
You've measured the output of the 555 at 31kHz which going by the values is right if the 555 is wired using only R3 (1k), R2
(10k) and C2 (2n2). Which I believe is how you measured 31kHz.
R1(56k) and bc547's collector on the control pin would be affecting this ratio to get it up to 45kHz, or in my case at 90v, down to 18kHz.
I havn't got a datasheet handy. Would this change the frequency or the duty %age?
I'm pretty sure that's what's going on. I was a little confused because of the discrepancy between what I'd measured and the spec'd frequency, but since I'd taken most of the rest of the circuit away I just figured that the rest of the components would cause the frequency to change when they were added back in. The only troubleshooting tip in the notes said to check the output of the 555 if the circuit wasn't working...now that I know it's oscillating I'll hook up the rest and see what's happening.
I was too busy with school to work on it again until yesterday morning, but after a couple false starts I was getting 200-300v without a load! When it's powered up it starts putting out 230-340, which gradually drops to 200-300v over a minute or so. Now I gotta solder it all up!
tres utile et interessante si vous parlez francais, mon amis!!!
(j'ai etudiè francais à l'ècole, beaucoup d'annèes sont passè...)
-.-
http://techniguitare.com/forum/realisation-montage/alimentation-decoupage-12v-300v-sg3525-t7791.html
Quote from: Renegadrian on July 17, 2011, 05:31:09 PM
tres utile et interessante si vous parlez francais, mon amis!!!
(j'ai etudiè francais à l'ècole, beaucoup d'annèes sont passè...)
-.-
http://techniguitare.com/forum/realisation-montage/alimentation-decoupage-12v-300v-sg3525-t7791.html
Google Chrome's Translator works well in this case
shouldn't this be called "charge pumps" thread.?
i built i tremolo with this "multiplier", rick mentioned rick earlier and its discussion was dropped.
>>
Re: Voltage Multipliers (for our tube projects...)
« Reply #79 on: May 31, 2009, 02:58:07 AM »
I found this over at AX84 forum, thought it may be useful to some folks:
PDF: http://ricktone.rickcampbell.org/cgi-bin/getimg.cgi/PedalPowerSupplyLayout.pdf
Link to thread: http://www.ax84.com/bbs/index.php?id=385353
<<
my comment is isn't brute force and lower part counts better except for space considerations ?
http://electricwestern.com/diytubes.html
seems interesting...
Im just using small power transformers at this point. There are some cool toroidal's im going to try when i get the cash.
Here's my version of the nixie power supply described in numerous posts above.
(http://www.aronnelson.com/gallery/main.php?g2_view=core.DownloadItem&g2_itemId=46579&g2_serialNumber=2)
(http://www.aronnelson.com/gallery/main.php?g2_view=core.DownloadItem&g2_itemId=46573&g2_serialNumber=2)
If you build this layout, don't forget the jumper under the 555.
(http://www.aronnelson.com/gallery/main.php?g2_view=core.DownloadItem&g2_itemId=46576&g2_serialNumber=2)
Here's a link to the full-size PCB image: http://www.aronnelson.com/gallery/main.php?g2_view=core.DownloadItem&g2_itemId=46574&g2_serialNumber=1 (http://www.aronnelson.com/gallery/main.php?g2_view=core.DownloadItem&g2_itemId=46574&g2_serialNumber=1)
They work great. Now I just have to find something useful to do with them. I have a few spares if anyone is interested.
http://powersupplycircuit.net/wp-content/uploads/2011/07/dc-to-dc-converter-circuit.gif
I am looking for ways to achieve 50-150v @ 10mA for submini tubes.
Reading this thread a few times I think the two most useful candidates are the much discussed Nixie power supply and Harry Lythall (SM0VPO)'s multiplier design.
Nixie here: http://www.ledsales.com.au/kits/nixie_supply.pdf (http://www.ledsales.com.au/kits/nixie_supply.pdf)
Harry's here: http://www.sm0vpo.com/power/vconv_01.htm (http://www.sm0vpo.com/power/vconv_01.htm)
The Nixie is a great unit but as designed it is adjustable between ~100 and 200v and can put out 10mA. Perfect! But I would like the voltage to start at a lower point ~50 V or so. I think to get it lower, its simply a matter of adjusting the feedback voltage divider, reducing the 220k resistor (R5 on the schem). What I'm unsure of is the effects this may have on oscillator noise (actually I am unsure of many parts of this Lol).
Sungist mentioned on the previous page measuring 18kHz with the trimmer fully adjusted down to 90v with this unit which would possible cause noise.
So how to lower the starting voltage and keep the oscillator out or audio range?
Harry Lythall's design is very simple. He says it can produce 1-2 watts of total power and states it will do 100mA @ 24v which I get as more like 2.4 watts. This up-scales to 50mA @ 36v (1.8watts) and 30mA @ 60v (1.8watts) so approximately 10mA (maybe) after losses @ 150v if you build that many add on stages.
(http://i2.photobucket.com/albums/y16/stm88/edssw3-1.png)
I would like to build this, but using a beefier transistor pair for more "reserve" current.
Any suggestions as to best replacements for the BC547/557?
OK, while I am waiting for my Inductors to arrive I have put together this:
(http://i2.photobucket.com/albums/y16/stm88/CWaltoncompact-1.png)
It 'aint the most compact thing but by utilizing the %^&*roft-Walton capacitor approach, you can get up 93v from a 9v supply, using common low-voltage caps and no special components required. I used all 33uF 16v caps, simply because I had a bag of them. You can pretty much build this from any types you have within reason over 10uF. You can also use other common tranny types such as 2n3904 for the astable multivibrator bit. I used a combination of 1n4001 followed by 1n4148 for the diodes which are a bit lossy.
Obviously as voltage increases, current is reduced so you will only see 3-4mA at 90v but that may be OK for some single tube designs. At lower voltages there is much more current to play with. You can tap off whichever voltage you need or build it up to the required voltage. You could also tighten the layout up a bit if you wish. I built it as shown with PCB pins so I can tap off different voltages.
Schem is in post above, layout is verified
NOTE: Even at low current please take care with higher voltages
EDIT: Had to change the image link. (willy word in the title)
(http://www.a-reinert.de/Dekatron_A101/32_DC-DC-Wandler_12V-450V_10mA_Schaltung.GIF)
nice, but 10mA enough to power just one tube?! I don't remember the usual plate current of the common tubes, but 10mA is really low...
1-2ma for a 12ax7.. should power a full preamp rack unit!
Hi!
I build this 555 voltage multiplier - seems to work. I want to put it in my tube pedal with one or two 12ax7.
Right now, I just switched it on alone, not buid in any pedals... I am a bit afraid of the high voltages.
If I connect the metal housing of my pedal to the gnd (signal and voltage multiplier) - will I be safe than? What else should I pay attention to - just to avoid dying?
Quote from: Dongle on May 06, 2014, 08:57:39 AM
Hi!
I build this 555 voltage multiplier - seems to work. I want to put it in my tube pedal with one or two 12ax7.
Right now, I just switched it on alone, not buid in any pedals... I am a bit afraid of the high voltages.
If I connect the metal housing of my pedal to the gnd (signal and voltage multiplier) - will I be safe than? What else should I pay attention to - just to avoid dying?
Voltage multipliers have notoriously poor regulation - the voltage may drop some if you touch it (but don't touch it just to check). I have been repairing and restoring antique radios and televisions since I was a teenager in the late Jurassic period and it is possible to get a shock but if you follow safe practices like not holding onto anything grounded, you will be OK. In fact it was far more common for me to get burns from hot tubes than any electric shock injury. Once you ground the negative side to the chassis, it would be more possible to get into trouble with the positive lead because now you have a large grounded box to touch as well. You should also follow the star grounding schemes recommended in a few other threads where all ground connections are brought to one point so that you don't get ground loops that allow current to flow from one grounded point to another and add noise.
Check the voltage you are getting at the output. Each triode in a 12AX7 is normally operated below 2 mA and is usually 0.5 to 1 mA. The filter capacitors store most of the charge and this is where current will come from if you touch it. If you are measuring voltages, make sure your hands do not contact the metal part of the probe, but most test leads have an insulator with a hilt on it to make sure there is little possibility of coming into contact with high voltage.
Alright... thanks!
Still I am wondering: If I have that thing ready in my pedal and do not connect the housing to anything - than I might get 200 V on the housing if I get a failure (loose cable etc).
So O thought, if I connect it to ground, the circuit would be short - that would not be dangerous and one would notice the failure...
The housing will eventually have to be grounded at one point, usually the input jack, to avoid noise pickup from having the housing floating. If you are testing the power supply with the housing floating and it accidentally touches the +200 volt line, then the rest of the voltages in the circuit will be negative with respect to the housing. But as I said, with reasonable care, you should not run into any danger with a 200 volt supply that can only supply a small current. The televisions that I worked on in the past have had 270 volt supplies with 150 mA capability and that is not the highest voltage in the set - the damper supply was usually 550 volts and the high voltage to the CRT was in the range of 12,000 to 25,000 volts. Only rarely would anyone get into trouble because all probes are insulated for any test equipment you would want to use.
Just adding another one to the list:
(http://i81.photobucket.com/albums/j207/merlinblencowe/c0a50662-9978-4a5c-a600-f58cd27b03d2_zps38wxt8u8.png)
Just dropping by to say wow, this is a very useful thread! I've come into possession of a reasonably powerful laptop PSU (19VDC@7.1A) and I was toying with the idea of building a hybrid amp and the converters here will be ideal! I'll be sure to post up my build when it is on its way. I'll probably start with something like an Alembic preamp with an output buffer/loop into a cheap class D poweramp board.
Hi Zozobra, welcome to the forum! Yeah, this is a very neat thread, really useful info on how to power your tubes without laying out the ca$h for transformers. I'm also working on some flyback-type power (just the nixie stuff, nothing special), and was checking out the schematics here, and saw your post.
So, you want to go tube pre, to SS output? Not a bad choice if you don't want poweramp distortion. Preamp dirt is easier to control, more predictable :)
Thanks :) A few of the regulars will no doubt have seen my witterings on other techy forums.
That's the plan. I've built quite a few push-pull tube amps and I fancied trying something different. Certainly hybrid amps like the Matrix VB800 and Verellen Kalaloch look very interesting and it would great to have a light weight, high power pedal platform in the arsenal!
also hello Zozobra, and are you planning for 6V or 12V heated valves?
Since we're reviving this thread, it seems...has anyone been able to source the 100uH inductor lately?
I've been thru my usual haunts (Mouser, Newark etc) can can't seem to locate a suitable replacement - the listed parts appear to be out of stock permanently...
Quote from: GibsonGM on May 21, 2016, 04:21:30 PM
Since we're reviving this thread, it seems...has anyone been able to source the 100uH inductor lately?
I've been thru my usual haunts (Mouser, Newark etc) can can't seem to locate a suitable replacement - the listed parts appear to be out of stock permanently...
Another option would be to wind your own, it takes less than 20 minites to wind, You only need about 10 ft enamel wire and a ferrite rod core...
Quote from: sajy_ho on May 22, 2016, 05:28:19 AM
Quote from: GibsonGM on May 21, 2016, 04:21:30 PM
Since we're reviving this thread, it seems...has anyone been able to source the 100uH inductor lately?
I've been thru my usual haunts (Mouser, Newark etc) can can't seem to locate a suitable replacement - the listed parts appear to be out of stock permanently...
Another option would be to wind your own, it takes less than 20 minites to wind, You only need about 10 ft enamel wire and a ferrite rod core...
Yeah, but what kind of core, how to figure out what's up with that? I have ferrite AM ANTENNA core up the ying yang...a couple of power inductor cores, but no way to know what the value of uH would be, how many turns and so on...
two transistor LC oscillator - cro/counter - some 5% tolerance caps - paper and pencil - the formulas.
wind on 10, 15, even 20 turns of any wire to hand, hook-up wire even. put it in the osc, read the frequency for each value cap. do the calcs for freq, Al, and inductance. once you have the Al for a particular size/type chunk of ferrite, you can calculate the # of turns for a given inductance.
or, just find the Al, then find the interwebs cheat page for the other numbers. but the long way is much more funn-er.
No need to wind anything:
(http://diyaudioprojects.com/mirror/members.aol.com/sbench101/BatteryPoweredAmps/3vHiFi.gif)
This is from:
http://diyaudioprojects.com/mirror/members.aol.com/sbench101/BatteryPoweredAmps/3vHiFi.gif
Yeah, Duck, kind of like I supposed...eventually I will find a source to just purchase a few 100uH inductors, LOL! Lotsa work, not having many cores to choose from and so on. I only have 2 of the type I had told you about, which MAY be enough, anyway!
Thanks Tramp, I'm used to/enjoy the high B+ preamps, like the GTFO. Really curious about all the hubbub around these small power supplies!
Little more effort yielded: http://cpc.farnell.com/1/1/18834-murata-power-solutions-1410454-inductor-100uh-5-4a.html (http://cpc.farnell.com/1/1/18834-murata-power-solutions-1410454-inductor-100uh-5-4a.html)
Beefy, 5.4A, just since others have reported too much heat with a 1A inductor...
Quote from: duck_arse on May 21, 2016, 11:23:01 AM
also hello Zozobra, and are you planning for 6V or 12V heated valves?
Hi :)
I'll probably regulate to 6V for parallel heaters as I have an EF86 that I want to experiment with in the input stage. I need to dig out Merlins power supply book to look up some regulators. Hopefully a 7806 will do the job. I recall there being a bit in the book about using them for low current heater supplies.
gibson - I believe there are people that own LCR meters. those people would wind some turns, measure the indutance, calc the Al, then wind the right # turns and remeasure. but I'm quite sure those people don't know half the fun.
Zozobra - I, too, have a (6GW8) 6 volt valve amp planned ....... to build, powered from a 19V laptop supply. and, transmogrifox, one of our members, suggested a circuit that boosts the 19V to 25V, to run the heaters on 6V, based on his high-voltage boost circuit. less waste heat.
this thread:
http://www.diystompboxes.com/smfforum/index.php?topic=112122.0
Thanks. I'll have a look at that. After years of doing turret builds I think it's time I gave designing a PCB a shot. I have access to a desktop miller at my local fablab and I'll need to go there to fab the chassis and sleeve so I have no excuses now really.
Let's revive it again :) I built a typical Nixie supply from one of the usual schemas floating around.
What I found is consistent with others' results...you need to turn the adj pot down until you get minimum hum. Now, using a manufactured inductor, I can get 220V or so before the hum is too great. Using one I rolled on my own, I can only do mid-100's before the hum is bad. This suggests the "Q" or some other property of the L is in play. So, buying one is probably best, or becoming REALLY GOOD at rolling your own, ha ha.
I still want to filter this thru an R-C network, maybe 2.2k with 22u to ground, 450V rating, to remove the rest of the 120Hz hum. Already tried this, it seems to work, and I am still maintaining about 210V with a 24k load (for just under 10mA, way more than needed).
You could always use a cold-cathode shunt voltage regulator tube:
(https://s-media-cache-ak0.pinimg.com/736x/3a/31/57/3a3157c3258b96f5b4d16ad7ce03f54c.jpg)
The pink ones are argon-filled and the orange ones are hydrogen-filled. These tubes are used as shunt regulators and the only differences in using them as opposed to zener diodes is that they strike an arc at a voltage a little above the running voltage, they should not have any capacitance directly across them or they will become relaxation oscillators and they have minimum as well as maximum currents. I acquired 15 0B2's recently in a box lot and intend to use them in some receivers and FM tuners to stabilize operating voltages. You can get 7-pin miniature or octal tubes and voltages of 75, 90, 105 and 150 volts. The 7-pin tubes regulate between 5 and 30 mA and the octal tubes regulate between 5 and 40 mA. They can reduce hum to a value below other noise levels and you could use two 105 volt tubes in series to get 210 volts.
Cool! Altho it's another heater to power. I'd like to stick to R-C filtering, if it's possible. But thanks for that, totally another avenue I hadn't considered! Yesterday's voltage regulators :)
Quote from: GibsonGM on June 09, 2016, 09:27:53 PM
Cool! Altho it's another heater to power. I'd like to stick to R-C filtering, if it's possible. But thanks for that, totally another avenue I hadn't considered! Yesterday's voltage regulators :)
These are cold-cathode tubes - no heater at all. I like replacing tube rectifiers with silicon diodes then using the empty socket for a regulator so the voltage is limited as soon as the unit is switched on. Just give each tube 10 volts more than the running voltage to strike, don't add capacitance to bypass them and set the resistor values to stay above 5 mA and below the maximum current and you can kill the hum and keep the voltage within a few volts from minimum to maximum current. Check the 0B2 performance here:
http://tdsl.duncanamps.com/show.php?des=0B2
Thought I'd point out that these boost regulators are now commonly available on eBay for pennies. Described as:
"8~32V to 45~390V DC-DC Boost Converter ZVS Step-up Booster Module Supply"
Although it says it's good for 40W output I have found that 25W is a more reliable maximum for continuous operation. Above this the transformer gets hot.
(https://s18.postimg.org/3xs6j538l/fox.jpg) (https://postimg.org/image/3xs6j538l/)
I bought those boosters but have not used them with any large load. I have bought universal switching wallwarts for low voltage and found generally they do not do the rated current on 120V but will do it on 230V. I am hoping to use the 390V booster for a 6V6 amp with 12V tubes and a brick PS. The booster is not isolated but the 12V brick takes care of that.
How does the ZVS supply do as far as noise goes? Are you able to get fairly clean power from it? I've never worked with ZVS's before, but for $5 it may be worth a try.
Quote from: vigilante397 on March 22, 2018, 11:41:19 AM
How does the ZVS supply do as far as noise goes? Are you able to get fairly clean power from it? I've never worked with ZVS's before, but for $5 it may be worth a try.
I'd assume that, because the switching speeds are so fast, there isn't a whole lot of noise associated with them. You'd plan some filtering into your design, anyway, so they GOTTA be use-able. If the one I haphazardly BUILT is so quiet (and it is), I'd be more than willing to give one of those a shot!
100uH isn't a magic number. If making a boost converter of some sort you can probably work with anything between 10uH and 1mH, and then you change switching frequency to make it work where it's happy.
LTSpice is a good tool for working out the best switching frequency -- and there's nothing wrong with operating in continuous conduction mode as long as you have a beefy enough MOSFET to hand the switching losses.
I'm making this alive again. I' sorry. I built this smps but thr voltage keeps on faling on some time then rising again. I dont know why. :( it starts with 270 ish. Ofcourse when the tube heats up properly, it will slowly drop the voltage of the plate. So it goes down and down. But when it hits some voltage. For example from 270 to 180v then it will rise up again. What could be the problem.
Quote from: johngovan1234 on October 25, 2018, 09:00:53 AM
What could be the problem.
Sooooo many things ::) Can we see what schematic/layout you used for your build? Perhaps some pics of the build? The only times I've had roaming voltages I wasn't able to control on an SMPS build was because I left out a component or two, which is unfortunately common because with tube builds I always stuff the power supply first and leave everything else off until I can get power right.
This one Sir. The voltage keeps on flactuating. It doesnt stabilize at certain voltage. Almost dropping 1mV every 2 seconds. My startup is 270vdc at the B+. Then it goes to 263vdc when the tube heats up. Then it will keep on fluctuating a milivolt every 2 seconds. Is this normal?
(https://i.postimg.cc/9417GCp4/555SMPS.gif) (https://postimg.cc/9417GCp4)
Low frequency motorboating?
From your first post it sounded like it was oscillating between 270V and 180V, that would be really bad. Probably some faulty part, or missing resistor in the feedback network.
But milivolts sounds OK. There are PSUs with more ripple than that.
I use basically the same SMPS, my most common mistake is to leave off the 220k feedback resistor. Check to make sure you did everything right, and if so, like thomasha said wandering millivolts at a time is not a huge deal.
what transistor did you use, BC54x? photos of your build?
It might be normal if it's only a few mV - but any electro cap on the HT is under the stress of high voltage. It could be you have one or more that isn't 100% formed, or a bit leaky anyway. I would leave it on power to soak for a while. An hour or so.
Quote from: merlinb on March 22, 2018, 10:22:48 AM
Thought I'd point out that these boost regulators are now commonly available on eBay for pennies. Described as:
"8~32V to 45~390V DC-DC Boost Converter ZVS Step-up Booster Module Supply"
Although it says it's good for 40W output I have found that 25W is a more reliable maximum for continuous operation. Above this the transformer gets hot.
(https://s18.postimg.org/3xs6j538l/fox.jpg) (https://postimg.org/image/3xs6j538l/)
The listing had been taking down. But I wanted to chime in on this. I've bought two of them. Didn't realise they installed one of the HV capacitors backwards and it blew up in my face. Took a whole day to air out the workshop and for things to smell right again. Be weary when using the cheap boosters.
This was the image from the listing and what I had received;
(https://i.postimg.cc/XXQrs699/booster.jpg) (https://postimages.org/)
QuoteBe weary when using the cheap boosters.
This was the image from the listing and what I had received;
The EI cores are going leak out more field than a shielded inductor.
However, they are probably better than an unshielded bobbin core.
ZVS looks like something to try.
I came across this interesting boost converter variant over the last 6 months or so,
(http://diyaudioprojects.com/Tubes/12AX7_Preamp/F02psschematic.jpg)
It uses an autotransformer instead of a straight inductor. This lets you get better efficiency when the voltage conversion ratio is large, like it is for a tube supply. It's perhaps possible to adapt that idea to the 555 circuit.
The down side is you have to make you own coil. Parts for making your own shield inductor aren't so widely available.
I'm set with HV pedal designs for a little while. I nearly finished my Tube-O-Vibe and was sorting out the on-board SMPS after success with the cheap booster - or the one that didn't have a backwards capacitor. I'll dig back into it eventually when the PTSD wears off.
That cheap booster uses a ZVS with a flyback so it doesn't use a straight inductor... however its voltage jumps about a lot!
So... what's the deal with the 680k 1W resistors? Even if it were just one that should be way less than 1W of dissipation, a 1/4W should be fine there.
QuoteSo... what's the deal with the 680k 1W resistors? Even if it were just one that should be way less than 1W of dissipation, a 1/4W should be fine there.
I suspect the reason has more to do with voltage rating and reliability. A 1W resistor typically might get a 400 to 500V DC rating. A single resistor roughly meets the cap voltage of 450V (I don't have the original article so I don't know what max voltage they are targeting.) Two 1W resistors would give good reliability. However, three might be more to do with with the magazine's paranoia of people sub'ing parts and getting sub-standard parts in the open market. Like if the resistors only met 250V then you probably would want three of them. All speculation on my part but those types of things do go through my mind when I see HV stuff, especially when the device could be left on permanently and the resistor is permanently stressed.
In 240V mains countries it's pretty common for switch-mode power supplies to not start-up when they get old (3 to 5 years). This is usually due to resistors going high-resistance because they are subject to high-voltage for long periods. (Nowadays the caps fail before that happens ;D)
Quote from: Rob Strand on February 21, 2019, 07:13:27 PM
I suspect the reason has more to do with voltage rating and reliability.
So what you're saying is that if one of my 200V supplies ever failed, the 1/10W 150V rated resistors could possibly be to blame? :icon_eek:
I'm shocked! Well maybe not that shocked.
QuoteSo what you're saying is that if one of my 200V supplies ever failed, the 1/10W 150V rated resistors could possibly be to blame? :icon_eek:
Probably not a good thing in the long term.
For that feedback resistor, I suspect the fault you would see is the voltage would rise-up over time. The cause is the rising resistance. You probably wouldn't notice for a while but at some point the voltage would get to a point where the circuit behaves weird or it could over-voltage the filter cap and pop it. For an effects pedal that isn't on 24hrs a day it could take a while to fail. As the voltage goes up it stresses the resistor more and more. In theory it could arc through the resistor (on a small scale). Apparently you can get micro arcing on resistors and perhaps outright arcing but I have not seen this myself in the low hundreds of volts.
Quote from: vigilante397 on February 21, 2019, 05:53:40 PM
So... what's the deal with the 680k 1W resistors? Even if it were just one that should be way less than 1W of dissipation, a 1/4W should be fine there.
Yes 1/4W is fine there, since the voltage is also shared evenly between them.