Author Topic: Another non-working NPN boost  (Read 7808 times)

Tranin

Another non-working NPN boost
« on: March 01, 2007, 10:14:07 PM »
Hello,
I just found this site in the last week or so, and I went out and purchased all the necessary items, put it all together, thought I actually might have gotten it, but I bet you can guess....It didn't work. I've read through many of the previous posts, and checked a few issues, and think I actually solved one or two small issues that I did have, but alas, I cannot get it working properly. The problem I'm having now is that when I use the boost, it is actually cutting my signal by alot. If I hit the strings real hard, I get that real bassy distorted sound, and it seems to be easier to make the distortion as I turn the pot up. From what I read in a previous post, it sounds like possibly a misbiased transistor. I measured all my voltages and have a picture with all of them. Let me know if there is any information I'm not providing that you need. Just a quick note, I don't have a switch at all, and I'm using two stereo jacks, so on the output jack, tip is output signal, and sleeve is to ground, ring is disconnected. Sounds right to me, but just thought I'd add that as well.


GibsonGM

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Re: Another non-working NPN boost
« Reply #1 on: March 01, 2007, 10:39:27 PM »
OK Tranin, let's have a look  ;)  Yes, I"m sure the transistor sounds misbiased, that happens a lot.  But first:  is the transistor installed in the correct orientation (you know, is the pinout right?).  It's very common to put one in backwards by mistake!!  So you might start there, double check with the package it came in or a data sheet.  Another common error is a 'solder bridge', where you short out 2 places that aren't supposed to be connected.  A close look often reveals these  8)

Are your electrolytic capacitors pointed in the right direction?  They're polarized, so have to be oriented properly. 

Now that I look closer, look at your pot...do you have a wire going to the wiper (center) rather than the opposite (ground) lug??  If so, there's your trouble, the output wire goes right to the lug marked with the 4.87.  Make sure of that, ok?   

There's a few things to try...if it's none of those, try posting an actual pic of your board, and we'll look further!  Good luck

 
MXR Dist +, TS9/808, Easyvibe, Big Muff Pi, Blues Breaker, Guv'nor.  MOSFace, MOS Boost,  BJT boosts - LPB-2, buffers, Phuncgnosis, FF, Orange Sunshine & others, Bazz Fuss, Tonemender, Little Gem, Orange Squeezer, Ruby Tuby, filters, octaves, trems...

Tranin

Re: Another non-working NPN boost
« Reply #2 on: March 01, 2007, 11:11:09 PM »
Thanks for the fast reply!

Alright, I tried the transistor in both ways, but, I have verified from the packaging that it is definitely in the correct orientation.

I looked for solder bridges, and even looking closely, didn't really see any that looked like they were actually touching, so I don't think thats the problem, but I'm always willing to try scraping in between a few later to see if that helps.

All the electrolytic caps are pointing the correct way, negative side away from the input cap. You should be able to see in my pictures.

Yeah, the way I put the voltages on the pot was a bit confusing. I have a pic for this one too, but to answer your question, no, one outer lug has the signal wire, the other outer lug has ground, and ground is the one that shares the negative side of the electrolytic cap on there. I was trying to illustrate that I believe the pot is working correctly as the voltage is 4.87 when pot is all the way clockwise, and it drops all the way down to 0 when its all the way counterclockwise. Sorry for any confusion there...

Instead of posting three pics in here, I'll just provide you the links for them. And just a quick note on the bottom side of my board, when I went to radio shack, they gave me a .01uF cap instead of a .1uF cap, didn't realize this until after I put it all together, so, instead of desoldering(as I don't have the necessary tools to do that at this time) I just bent it off, and then soldered the new .1uF one spot below it. Just didn't want that raising any questions. Now for the pictures!

http://socks.hopto.org/guitar/bottom.jpg
http://socks.hopto.org/guitar/pot.jpg
http://socks.hopto.org/guitar/top.jpg

aron

Re: Another non-working NPN boost
« Reply #3 on: March 02, 2007, 04:00:44 AM »
Can you show another picture of the top of the board with all resistors shown? I wonder if it's a mistake in one of the resistor values?

GibsonGM

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Re: Another non-working NPN boost
« Reply #4 on: March 02, 2007, 08:26:45 AM »
You're welcome, Tranin...we like to help around here, it's actually part of the hobby!
I can't see anything glaringly wrong in the pics (nice job, actually). I'm with Aron, there could be a wrong value resistor in there.   This is where we do the debugging procedure  8)

What are you using for a transistor? Do you have a 2nd new one you could swap in there in case the 1st one died?   Is your power coming in thru that 10K resistor? Must be the one behind the transistor?  That affects biasing and sets current.

That aside...do you know how to use an audio probe yet? That can tell you where the problem is, or at least what point it's working up to.

I'm going to make this and check my voltages, I will check back here later on (now I'm curious what's going on, LOL).    Keep the faith, we'll get it going!

~Mike
MXR Dist +, TS9/808, Easyvibe, Big Muff Pi, Blues Breaker, Guv'nor.  MOSFace, MOS Boost,  BJT boosts - LPB-2, buffers, Phuncgnosis, FF, Orange Sunshine & others, Bazz Fuss, Tonemender, Little Gem, Orange Squeezer, Ruby Tuby, filters, octaves, trems...

GibsonGM

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Re: Another non-working NPN boost
« Reply #5 on: March 02, 2007, 09:35:13 AM »
It's a snow day here (no work), so I built the boost....maybe Aron would like to snag the image and put it in the help section or something (?).   I get the following voltages:



I think you should work from the outside in, Tranin, and make sure you get something close to these.  See how the base and emitter are about .7V apart? That's what you need to see with a transistor (it's a 'diode drop', universal to BJT's).   Where you get a screwy reading is likely where the mistake is (or it is connected to something that's screwed up).  The readings should be close, but not exact.  It's useful to probe from the top so you can actually see which part you're dealing with and write the values on a print of the schematic.  If one of your resistors is the wrong value, that would mess things up!   
 
Hope this gets you going...I like this boost, haven't made this particular one before.  A lot more transparent than say the LPB-2 or Big Muff boost section.
MXR Dist +, TS9/808, Easyvibe, Big Muff Pi, Blues Breaker, Guv'nor.  MOSFace, MOS Boost,  BJT boosts - LPB-2, buffers, Phuncgnosis, FF, Orange Sunshine & others, Bazz Fuss, Tonemender, Little Gem, Orange Squeezer, Ruby Tuby, filters, octaves, trems...

Tranin

Re: Another non-working NPN boost
« Reply #6 on: March 02, 2007, 09:52:37 AM »
Can you show another picture of the top of the board with all resistors shown? I wonder if it's a mistake in one of the resistor values?
Well, I just got to work, but I have to go home early today, so I'll take some pics when I get home. To be completely honest with you, it wouldn't suprise me if I got a wrong resistor in there, as I soldered in an incorrect value resistor and then caught the mistake, well, at least I thought I did.  ;D


What are you using for a transistor? Do you have a 2nd new one you could swap in there in case the 1st one died?

I am using a 2N2222, funny I failed to mention that at all before. I have tried two different transistors, the first one, I cut the leads down pretty short so it fit into the socket and wasn't taller than any of the other components, I figured I'd just try another one as these are the cheapy plastic ones from radio shack. I left the leads long on this one too, just for now anyway. They came in a 12 or 15 pack, so I can try more if you want, hehe.

Is your power coming in thru that 10K resistor? Must be the one behind the transistor?  That affects biasing and sets current.

Sorry, but I'm not quite sure I understand this question. I believe the power is coming in throug the 10K resistor at the top of the schematic. The voltage level drops(almost by half) once it goes through that resistor. I know resistors are used to create impedence, right?(Ok, I think, not know) But are they supposed to cause voltage changes? Computer nerd I am, but electrical engineer I am not, but hey I'm learning something new everyday, so that's always a good thing.

That aside...do you know how to use an audio probe yet? That can tell you where the problem is, or at least what point it's working up to.

Sorry, but I do not...

I'm going to make this and check my voltages, I will check back here later on (now I'm curious what's going on, LOL).    Keep the faith, we'll get it going!

I'm interested to see what voltages are supposed to be on a working circuit(other than the obvious small changes from the battery's charge.) I did see someone else post a pic similar to mine with all the voltages(actually where I got the idea) but they had some very different voltages, especially on the transmitter posts if I remember correctly, but I could be wrong there. Then again, they posted the picture because theirs wasn't working either at the time, so maybe thats not something to worry about.


Cheers for now, I'll get more pics as requested when I get home!

GibsonGM

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Re: Another non-working NPN boost
« Reply #7 on: March 02, 2007, 10:33:57 AM »
I think you'll get it working once you can go thru with the meter, man. 
A resistor creates a voltage drop, and causes a current to flow...when you have 2 in series from V+ to ground, the junction of the 2 makes a voltage divider where the voltage out = voltage in*(R2/R1+R2).   Look at it this way: a wire from + to - is a short; infinite current flows (very bad). That follows Ohm's Law, current(I) = voltage(E)/Resistance(R), or I=E/R.  The above is division by 0, or infinity.   A resistor inserted in series with battery poles resists that infinite flow, and dissipates heat (measured in power, or wattage).  So you get a current which is equal to the voltage divided by resistance.  It can get more complicated if there are other resistive components in parallel to the supply, though - the resistance of the transistor factors on that reading, too (after the 10K).  Often times it's easier to get something to work, then take measurements, lol.  The .7V drop from base to emitter says a lot about if the transistor is biased correctly.   There are about 4 or 5 important formulas to learn by rote, and you'll get it, if you are actually a computer geek  8)  Ohm's Law is first!  Tons of tutorials can be found by Google.    Since a transistor is a current-controlled device, getting those R's correct is crucial to proper operation!   

You should pick up a basic electronics book!  It did wonders for me, lol...I've been at this for about 5-6 years, learning more all the time.  Searching in the forum for "audio probe" and the like will show you what's up with that.  It would be good to mess around with one after you get this working to get the hang of it on a known working circuit... and using the continuity function of your meter can save a lot of hassle by showing if something is shorted that you can't see...

I whipped the thing together in 10 mins., and I know it's working (very well, I'm enjoying it!) - so I'm making the assumption that my voltages are correct as posted.  I also quickly simulated the ckt in Electronics Workbench, and the numbers are close (component tolerances can make things vary a little). So if you get close to those #'s, yours should work.  My transistor is a 2N3904, similar to 2N2222 but they ARE different, so the #'s will be a bit different, too. 

Keep messing with it, they get easier the more you build!  I can't say enough for reading the forums, searching Google for basic info/tutorials, getting simulation software like E.Workbench, using a breadboard, trying out basic things like voltage division...determination does wonders!
MXR Dist +, TS9/808, Easyvibe, Big Muff Pi, Blues Breaker, Guv'nor.  MOSFace, MOS Boost,  BJT boosts - LPB-2, buffers, Phuncgnosis, FF, Orange Sunshine & others, Bazz Fuss, Tonemender, Little Gem, Orange Squeezer, Ruby Tuby, filters, octaves, trems...

Tranin

Re: Another non-working NPN boost
« Reply #8 on: March 02, 2007, 02:04:33 PM »
A little short on time right now, so I've got to make this one short, I can do some more voltage checking a little later. I snapped another picture of the top of the board, and it's a little hard to make out the color codes, so I just labeled them on the picture so there is no confusion. I also snapped a picture of my color code explanation from the pack of resistors, not sure if its a dead set standard, or if it just depends on the brand you buy.

So here are the pics:
http://socks.hopto.org/guitar/board.jpg
http://socks.hopto.org/guitar/colorcodes.jpg

Tranin

Re: Another non-working NPN boost
« Reply #9 on: March 02, 2007, 05:20:56 PM »
Alright...got back home, and did a little fiddling around...and then I realized something...I actually *DID* have the transistor in backwards... :icon_redface: I forgot that when you are looking at a schematic, you are looking at the bottom/back of the board, not the top...soooooo stupid. In any case, I had tried it both ways before, with no success. The only thing I did do, there was the solder between the collector and base looked like they were very close together, I couldn't actually see them touching, but I ran my razorblade through it a few times, not sure if that actually made any kind of difference.

 I think I've made some progress, but I don't think its working quite right yet...I get sound, and the pot makes a change in the sound when I turn it, it seems to act like a tone control in a way, ends up bringing the bass and mids through a lot more, but not the highs. Also, it is always quieter than if I plug directly into my amp, so there is still something that is not quite right.

I did measure readings from the top this time, and I just used your pictures and replaced the values. I actually did it with two different transistors, don't know if you really need to see both, but I'll post them just in case.





GibsonGM

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Re: Another non-working NPN boost
« Reply #10 on: March 02, 2007, 06:00:38 PM »
Hey man,

Good work getting those #'s read.  I'd re-melt the socket connects there, that seemed shorted (without a transistor in place)...while, hot run the blade or a very small screwdriver thru there to assure there's not a bridge there, or it could waste your transistor.  One way to know for sure is to check the continuity between the socket connections with your DMM...I think there's enough resistance/caps in between them to prevent the meter from "seeing" them as connected if it's in right.  Slap a new transistor in when you know for sure, if you like - the old one is probably ok but it's a good practice. 

Best part for last, Aha, Aha!!!!  Yeah, resistors are universally color-coded (standard ones are).  That Yellow Violet Yellow one is supposed to be Yellow Violet Orange!!!!!!!!!    Yellow=multiply by 10,000   Orange = multiply by 1,000.  The real value is 47K.   That would explain many of the symptoms you report  ;D See how easy that was? Put the right one in and it might be all done....over time you learn how to read the colors pretty quickly.

To make life easier, here's a link to a spreadsheet i made.  I keep this over my workbench - common transistor and opamp pinouts, Ohm's Law chart, and those annoying color codes ;o)  Feel free to pass it around if anyone needs it.

http://www.rogepost.com/n/2797891865

Hope the thing works next time I hear from you!

~Mike
MXR Dist +, TS9/808, Easyvibe, Big Muff Pi, Blues Breaker, Guv'nor.  MOSFace, MOS Boost,  BJT boosts - LPB-2, buffers, Phuncgnosis, FF, Orange Sunshine & others, Bazz Fuss, Tonemender, Little Gem, Orange Squeezer, Ruby Tuby, filters, octaves, trems...

Tranin

Re: Another non-working NPN boost
« Reply #11 on: March 02, 2007, 06:42:21 PM »
Houston, we have BOOST!

Hmm...yes, apparently, if you put a 470k resistor where you are supposed to put a 47k resistor, it doesn't work, who woulda thunk it?

I think my ability to hear has diminshed slightly now  :icon_biggrin:

I plugged it into my solid state crate combo(2x12 with 120 watts) and with the volume on one, it boosted it up to about as loud as it is on 5(which is damn loud), and then started getting a kinda not so great overdrive to it, I'll have to try a coupld different transistors now that I got it working. I've been testing it on the solid state, too afraid to plug it into my new tube amp until I got it working right...but now I think I'll have to go see what it does on there.

CHEERS!!

GibsonGM

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Re: Another non-working NPN boost
« Reply #12 on: March 02, 2007, 07:27:56 PM »
Good work, Tranin.  Welcome to DIY  ;)

I love these little boosts, LOL.  I use one with my LP and 40W tube amp, it's insanity!  You can stick them everywhere, too, like after a fuzz face or big muff...and on and on.  That's why they make a great 1st project, they are really just a small 1 transistor amplifier.  You can set the gain if it's too much, it's the ratio of collector and emitter resistors, I believe.  There are whole articles on this on Google.

One cool trick to do, before you stick something in line with your precious amp, is to connect your - meter probe to ground, set for DC, and measure the output (tip).  You shouldn't get much more than a couple of mV if anything at all.   That's one way to keep them lovely preamp tubes from getting shocked, and I do it before plugging in any DIY build (if you short your output cap or something, there's your DC).  It's ugly when you get DC on your amp input, ha ha. 

Rock on, man! 
MXR Dist +, TS9/808, Easyvibe, Big Muff Pi, Blues Breaker, Guv'nor.  MOSFace, MOS Boost,  BJT boosts - LPB-2, buffers, Phuncgnosis, FF, Orange Sunshine & others, Bazz Fuss, Tonemender, Little Gem, Orange Squeezer, Ruby Tuby, filters, octaves, trems...

aron

Re: Another non-working NPN boost
« Reply #13 on: March 04, 2007, 12:06:46 PM »
Tranin,

Congratulations on your first debug! Good luck with your future pedals!

Aron

Gus

Re: Another non-working NPN boost
« Reply #14 on: March 04, 2007, 01:19:29 PM »
Tranin

   Your posts "sounds" like it is working correct.

  The original hand drawn schematic has notes on it.

  With 9 volts you can get maybe a x3 clean boost without running out of headroom using almost any kind of booster BJT,FET IC ...

  The min boost of the NPN is about X2 10K/ 5K

  The NPN seems to work its best guitar to NPN to a tube amp when the NPN starts to clip

  One could make this as a fixed X2 boost by making the 5 k pot a  4.7K or 5.1K fixed resistor and not using the cap at the wiper

  The design was for something a little different than the other boosts and allowing the use of different transistors if the stock resistor values are used.  One can change the cap values and types to taste.

Gus