hi!
ive built a fuzz face and it works fine until you turn up the fuzz. the sound gradually gets thicker at 50-70% and then thinner till it completely disappears at 90% and i just get short bursts of sound. its not a major deal as it is, but on stage it can be deadly(if any accidents happen).
(http://fuzzcentral.ssguitar.com/axisface/axisfacesi3schematic.gif)
(http://fuzzcentral.ssguitar.com/fuzzface/fuzzfacenpnschematic.gif)
ive combined the top schematic with the bottom one. i ve added a 100uf and diode(mine is 4001) and i added that cap (mine is 220pf) between the collectors.
note: the sound cut out before i added the other stuff.
help me out please!
Sounds like your fuzz pot is wired incorrectly. Make sure the cap is the only thing on lug 2 and lugs 1/3 are connected properly.
Quote from: mth5044 on December 28, 2015, 11:19:17 AM
Sounds like your fuzz pot is wired incorrectly. Make sure the cap is the only thing on lug 2 and lugs 1/3 are connected properly.
This, or a problem with the pot? Wiper intermittent kind of thing?
Quick spray with some pot cleaner could rule this out and is also beneficial...
ive tested the pot out with a multimeter and its giving me a clear signal. i also attached a cap just on 1 and 2 and the result is the same.
Check for solder bridges around the pot. You said you attached the cap on just 1 and 2, which is a little confusing. Is it on both of them? It should only be on lug 2. Do you have an image of your layout?
Quote from: mth5044 on December 28, 2015, 11:45:29 AM
Check for solder bridges around the pot. You said you attached the cap on just 1 and 2, which is a little confusing. Is it on both of them? It should only be on lug 2. Do you have an image of your layout?
Both the bottom of the cap and lug 1 of the pot connect to ground. Doesn't matter how you get them there, they ARE connected.
yeah sorry i was a fool. i did connect a cap on 1 and 2, but what i ment was 2 and ground seperating it from where other things are grounded.
BUT an interesting thing happend when i wired it correctly. the sound came at the 90% and up but when the guitar is idle it squeaks like crazy.
the squeak is actually a tone, the likes of witch a computer would make and is affected by guitar volume.
FUZZ:
vol 100
fuzz 100
Guitar
vol 90 and up (low pitch)
vol 90 and down (high pitch to no tone)
EDIT: You guys are too quick for me ;D
You can solder the cap right to the pot across the wiper and ground lugs AS LONG AS the ground lug is GROUNDED. Check to make sure all ground lines are connected including that pesky gain pot, it might not be.
Did you use a 10k trim pot to set the bias or just use the 8k2 fixed resistor? I've had some FF gain pots do similar things when the bias was off. Also, when the tranny gains were too low but I'm sure your Si gains are probably high enough.
Combined two circuits? Hmmm... I'm not sure about that...
I highly recommend measuring the tranny gains and plugging the numbers into Joe Davisson's Fuzz Face calculator... it's foolproof and provides instant satisfaction! ;)
i used a 10k trim and ive set it for 4.5v. it must have something to do with the RF oscillation, because FFs pick it up at 90%. thats my guess.
First check the stickyhttp://www.diystompboxes.com/smfforum/index.php?topic=29816.0 (http://www.diystompboxes.com/smfforum/index.php?topic=29816.0)
Silicon FF circuits need a good layout. They can take off when the gain is around max
Short wires,
Signals should cross at 90 degrees if you can't keep them far apart.
Good power supply filtering
A picture might help
4.5VDC is a web myth, people need to ignore that "web rule".
measure the collector voltages when the gain control is at a minimum and again when the signal cuts out.
A little off topic I tried a inexpensive 100uf electro as a power filter in a recent Silicon FF like build it turned out not to work correctly I had low frequency motor boating that when away with changing the cap to a better one.
What brand cap, something from china?
You can add a fixed resistor in the wiper to cap to limit the max gain. This is not a real fix
Q1:
C 1,2v
B 0,57v
E 0
Q2:
C 4,5v
B 1,2v
E 0,6v
values are the same no matter if its maxed or idle(fuzz)
the transistors are both BC108
update: it only squeels when the guitar vol is above 90%
up tu the 90% it buzzes
I see those two schematics have different input caps.
Did you use the .22uF input cap or the 2.2uF?
I don't really know if it makes a difference but I would stick with the traditional 2.2uF for a FF.
It might help with your guitar's interaction with the circuit, I dunno.
it the standard 2.2
Sounds like you did everything right. Maybe your guitar cable is acting like an antenna, you can try a small resistor in series right before the input cap, that is sort of what the "Smooth" pot would be doing (I think)
I've done this with some noisy FF's, I think I used a 100ohm resistor but maybe it was a little bigger than that. You'd think you wouldn't want to reduce your guitar's output into the fuzz pedal but some of my FF's had so much gain that it made no difference in the long run.
ok ive tried a 100ohm and it did nothing. ive tried a 100k and it removed the squeal, but there was a lot of hissing.
Hmm.. that's a lot of resistor... Remember what Gus said, 4.5v is a myth.... I always turn the gain up all the way and adjust by ear, volts be damned!
Cut-out at maximum gain suggests a layout problem. Output sneaks back to input and makes a squeal, often ultrasonic, which knocks-out the audio, sometimes with off/on action. Yes, the guitar impedance is part of the oscillations.
Short. Neat. Segregated.
a 100k on the 9V+ right before the coupling cap (100uf) seems to remove the squeal, but also makes every thing more bassy
(also now i can hear radio very clearly)
any suggestions?
update: i found out that a 220 does the right job, but it still squeaks a little on a PS.
it works a kind of treble boost. when guitar is idle it squeals, but when you play it the squeal occasionaly kicks-in in a form of a treble booster
update2: it is still oscillating just at a lower freq. the squeal has just turned into a buzz. its similar to 60hz, but the question is where? im running it on a battery
Still sounds like positive oscillation to me. I bet it changes pitch when you play with the tone knob. Your input and output are connected somehow -- even if it's through the air. I'm also going to suggest that it's a layout issue. Would you post the layout and photos of your build so that can be ruled out? Otherwise everyone's going to keep telling you the same guess. Adding resistors and such to the input and output is working around the issue without solving it.
Have you paid attention to my first post and PRRs?
LAYOUT is most likely what is wrong
4.5VDC is sometime correct
You can have problems with batteries
Is it in a metal enclosure?
How long are the wires?
How are the wires run?
Did you build it from a known good tagboard, perfboard or PCB layout?
yes tone changes as i turn guitar nobs
(http://s11.postimg.org/99pga1k5f/ddd.png)
(http://s27.postimg.org/bhlkt7fw3/12435604_10201351377902653_1699092966_n.jpg)
(http://s8.postimg.org/whnvj7l4l/12459571_10201351377582645_137137474_n.jpg)
(http://s12.postimg.org/80x7k362l/12435734_10201351377702648_334697345_n.jpg)
From the pictures showing the test leads and lengths of copper wires and the board being out of the enclosure. The wire lengths look to be the issue.
I would GUESS if you install it in the enclosure and make the wire runs short you might have a working effect.
Yikes! That set-up is asking for trouble. Your wires are long and probably picking up everything in the ether - radio, lighting, soldering iron... as well as it's own output. You'd get away with that for something simple like a treble booster, but not a high gain distortion/fuzz.
I can see at least 4 track cuts in that stripboard layout - I can't clearly see them on your board - are they all there?
Keep those wire's short. Use screened audio cable to make some croc-clip to 1/4" jack plug adapters so you can keep the audio connections screened as far as possible. Pots need to be close to the pcb when testing - even if you've got to unsolder them again to fit it in the box. You don't need to have the Footswitch involved until you've proved your circuit - not if it means having a lot of unscreened wires all over the bench.
You're nearly there, so clean up that wiring and get back to it!
You desperately need a breadboard. ;) And, I'd keep the entire enclosure out of the picture. I'd also wire the pots as part of the build with short insulated wires because I agree with Jim on the huge antenna you are dealing with above.
All of the above. Can't say one way or another what is going on, because you have antennae all over the place ;) Might not have ANY problems!
Keep 'em short, keep 'em shielded, see what you get...
Ya, it'll probably work fine once you get rid of the extra antennae and seal it up in aluminum.
Also, I thought I saw you might have a little extra unwanted bridge, so check and double check for that kinda stuff.
(http://a64.tinypic.com/35k7ms1.jpg)
Is that a solder bridge between the ground strip, 3rd hole (cap lead) that jumps down to the bottom-most strip? Looks like that is grounding the three bottom strips of the board (bottom two completely and the third up to the cut). (in Ben's pic, 3 holes right and 1 hole down from top left).
The approach I use for cutting traces is to have a drill bit handy and set it in a hole where the cut should be and spin it by hand until the copper is gone in a wide enough circle to cut the strip completely. Hard to accidentally bridge it, very visible, etc.
i shortened some wires and sealed it up AND the problem is still there. Dont worry about the solder joints they are not actually touching. it looks that way because the wire of the cap was at an angle and from that perspective it looks as if its touching.
first, i'd check your grounds. all of them. make sure they are solid. check all soldering nodes for cold solder, may pay to reflow the entire board.
but to me? sounds like you have really high gain transistors in there and they aren't biased correctly. 4.5v is a total myth. i've seen this happen with transistors that were misbiased many times.
make the connections to the gain pot as short as possible with stranded, not solid wire.
do not twist the wires together if you have done so undo it, less capacitance action that way.
i'd suspect the snubber cap you soldered in, but it sounds to me like the bias needs to be adjusted... there's two parts of that in a FF, the trimmer if used feeding the collector, and the fuzz pot itself.
also, make sure ya didn't use a 5k or 10k fuzz pot, cuz that could do it too.
make sure ALL THE POT CASES ARE GROUNDED TOO or it can squeal like a pig.