Help Debugging Fuzz Factory Clone

[platypy]

I'm a newbie at pedal building and have built a fuzz factory pedal, but it is exhibiting some problems. Sound comes through fine when bypassed, but when it is turned on it does not distort the sound at all, until the "drive" knob is turned up almost all the way. The volume knob is scratchy but works. All of the other knobs don't work at all, or only work a very small amount. For clarification, when turned on, clean sound DOES come through the pedal, but it is not distorted like it should be.
I used this layout from tagboardeffects: http://tagboardeffects.blogspot.com/2012/01/zvex-fuzz-factory-vero.html

I've triple checked the placement of the transistors and even tried turning them around (they're socketed) just incase the layout was wrong. Nothing's worked. What else should I be trying?

Here are the voltage measurements from each transistor. As I said, I'm fairly new to this, so if I'm missing any info, please let me know. 

Q1 = 2N3904
E = 0.00
B = 0.67
C = 5.72

Q2 = AC128
E = 8.23
B = 8.04
C = 1.37

Q3 = AC128
E = 7.97
B = 7.89
C = 1.87

Thanks,
Platypy

[antonis]

Hi and Wellcome... 

Clearly, your measurements are incorrect..

You can't have 7.97V on Q3 Emitter and 8.04 on Q2 Base..
Same for Q2 Collector and Q3 Base voltages (they should be identical..)

Also, your Q2 & Q3 V_EB voltage drops aren't enough for working on active region..
(I'm not familiar enough with Ge transistors but I think an Emitter to Base voltage difference of 80 to 190 mV is low..)

[duck_arse]

also welcome, also can you tell us your supply voltage at the board? also also, can you post some photos of what you have built, please.

[turning the transistors around? this indicates you haven't a copy of the datasheets handy .....]

[platypy]

Okay, so I re-measured my transistors, and these look a little more right to my untrained-eyes. Also, I'm using a 9v battery as my power supply. It reads as being 8.82v.

Q1 = 2n3904
E= 0.00
B= 0.66
C= 2.42

Q2 = ac128
E= 8.62
B= 8.47
C= 2.87

Q3 = ac128
E= 3.12
B= 2.90
C= 3.12

Here are some photos of my build:




Thanks so much for the help, guys! Just tell me if you need any other info.

[duck_arse]

hmmm, unfortunately, I (maybe even we) can't see those dropbox files. apparently they have 'made some changes'.

[antonis]

I should worry about your measurements in the same degree as with your transistors pin-out.. 

i.e. in spite of Q3 looks OVER-saturated (V_EC = 0) it's Emitter (standing on 3.12V) can't bias Q2 Base at 8.47V (even without feedback resistor at all..)

[platypy]

Okay, Stephen, I think I fixed the images. Dropbox got kinda whacked out, but I think it's all good now.
Antonis, I'm not sure that I follow what you're saying about the transistors. Are you saying that my measurements are still wrong?
Thanks again for the help!

[antonis]

Can't see well enough but your 4th & 5th rows seem short-circuited (at 12th hole..)

Check also for good fixation of transistor legs into sockets..
(it's a very common malfunction..)

I can't verify correct pinout for AC128s (2N3904 seems to be O.K.) but they both should face to the same direction, according to vero layout..
(base legs should be verically offset to the same side..)

P.S.
I leave resistors colour (de)coding to my down under eagle-eye friend.. 

[duck_arse]

nnnooooooooo !!!! not the colour bands! webbed feet, not eagle eyes. yr pics are loud and clear.

as antonis says - shorts. cutting those big holes thru the board is of little use if the tiny crescents of copper are left behind, doing their nefarious short-next-door work. at the very least, run a sharp knife between the tracks to cut anything that shouldn't be there, but ideally, you should get in with a scalpel or similar and trimm all the dags at the cut edges.

a question - why did you build it left-right mirrored? lucky you picked this layout, cause there's not many will withstand the mirroring.

also, can you find us a circuit diagram for that which you have built? is is polite to provide the schem as people really don't like trying to read a vero layout.

[platypy]

OK! I've got a distortion sound going now, instead of just clean! To do so, I got rid of those pesky little bits of copper and reflowed the solder to get rid of any shorts. I also decided to solder the transistors directly to the board, because the sockets I was using seemed very loose.
But now I have another problem: While the pedal does distort my guitar, it seems to only have a limited range of distortion, which is quite different from how a Fuzz Factory is supposed to sound. The only real change in distortion I can produce is either a decrease in volume (which occurs when turning almost every knob CW) or a decrease in sustain (which happens with a few different combinations of knob settings). It also doesn't oscillate at all, like a normal Fuzz Factory. Do you guys have any idea why this might be happening?

Also, I can't find the specific schematic that this layout is based on, but here is a similar schematic of a fuzz factory. It seems to be pretty much the same, I think, except the layout adds a 100Ω resistor between the +9v and the Stab control:


P.S. Stephen, I built it left-right mirrored because I don't really know what I'm doing and cut the traces on the wrong side. I didn't realize anything was wrong until I had populated the whole board. 

[duck_arse]

a mirrored layout seems to come around fairly often here, it's fine as long as you realise the implications, and do do it again. and never with an IC!

we need voltages on all your transistors again, please, turn all the pots, let's say clockwise, no input signal, and the supply voltage please. I think your Q1 C voltage is too low, maybe. I'm not much chop wit der npn's, but that antonis, he is a whiz.

also, please measure the resistances of the 220k and 10k attached to Q1 (always power off for resistance measure).

[platypy]

Here are the transistor voltages (all knobs were turned fully clockwise):

Q1 (2n3904)
E=0
B=0
C=0

Q2 (ac128)
E=5.93
B=5.93
C=5.75

Q3 (ac128)
E=5.92
B=5.72
C=.05v

I measured my supply voltage (a 9v battery) at 8.87v, but since the "stab" knob was turn all the way up, it cut the rest of the circuit's voltage to 5.97v, just fyi.

Also, I couldn't tell if you meant for me to measure the resistors outside of the circuit or not (I think you did, since measuring a resistor in a circuit doesn't seem like the most accurate thing), but I didn't have time to desolder them so I just measured them inside the circuit, incase that could be helpful. Tomorrow I'll be able to measure them separately.
Here are their measurements (inside the circuit):
220k = 220k
10k = 6.16k

Again, thanks so much for the help. I really appreciate it.

[antonis]

So you have a vary lazy (or absent and hopefully not dead) Q1.. 
(maybe 10k resistor is out of duty..)

Stab all the way up should result in NO voltage drop at all..!!

Plz, take out Stab from circuit (or short it with a jumper or an aligator clip wire) and make again your measurements..
(check also for 10k resistor both legs proper connection..)

Resistors don't have to be out of circuit for measurement as long as there isn't another resistor in parallel with them..
(power off, of course..)

[duck_arse]

it is unstated on the circuit dia which end of the pots is which, so I picked CW when I coulda picked CCW just as easily. either way, we seem to have turned up some sort of fault. the resistors in circuit will give some indication of goodness, as long as the values don't show ten times more/less (more or less) than marked. can we have revised pictures?

[platypy]

Ok, here are the measurements with Stab shorted with an alligator clip. By the way, I measured my battery at 8.85v, but the V+ input at the circuit was only 8.76 volts. Is that normal, or could it indicate a problem?

Q1 (2n3904):
E=0
B=0
C=0

Q2 (ac128):
E=8.75
B=8.75
C=8.65

Q3 (ac128):
E=0
B=8.65
C=0.06

Here are the revised pictures:





Also, I'm not quite sure what you mean about the Stab not having any voltage drop when it is fully counter clockwise, Antonis. Does this mean that, when fully CW, it shouldn't be cutting any voltage?

[duck_arse]

platy, we need to talk about images.

13. that's how many cliks I needed in the scrollbar to get to the bottom scrollbar to scroll across your images. I didn't count how many kliks were needed to go across, but I'm sure it's too many. and I'm led to believe there are people that have access to 'hand-held devices', whatever they are, which must have TINY screens. [really, what would people use hand-held screens for?]

anyway, you need to either resize your images to polite dimensions to post in the thread, or post smallish images as links to the original images, and let our browsers do the resizing/size to fit-ing.

and - the battery/board V difference shows us something about the circuit. if the battery reads 8V85, and the circuit end of the 100R reads 8V76, then you subtract the lower from the higher voltage to give you "the drop" across that resistor, then apply Ohm's law to find the current through that resistor. that resistor is "in series with" the rest of the circuit, so the resistor current  is the circuit current.

I'll away and look at your pictures now, but from a distance.

[duck_arse]

that vero layout you linked to - for some strange reason, all the transistors are shown facing the same way. Q1 is shown backwards for a 2N3904, and Q2 and Q3 would be facing opposite directions, not as shown. this helps you not a jot tho, cause yr Q1 seems to be deprived of all voltage by something I can't fathom. or see.

[platypy]

Oh man, sorry about the images! They looked totally fine before I linked them from dropbox. Should be fixed now.

I think that I'm going to go in with a voltmeter and trace the voltage all the way from the battery to Q1 and see if anything turns up. I'll let you know if/when I find anything.. Thanks so much for your help!

[platypy]

Ok, so I probed around a bit, and the 10k resistor is acting odd. The end connected to the stab control is, as expected, getting 8.77v, but the other end reads at 0v. This resistor supplies voltage to both the collector and base of the Q1 transistor, so it makes sense why this transistor isn't doing anything.
I even tried replacing the resistor with another that I had tested multiple times for conductivity (it read at around 9K), but the problem persisted. Do you have any idea why this would be happening? It seems very odd to me.

[duck_arse]

well, I was going to suggest doing resistance measures, but it seems you've narrowed it down somewhat. narrowed down to what, I'm not really sure - from all the red and black wires, I'd guess you've crossed one somewhere.

can you lift one leg of the 10uF in cap, and one leg of the first 100nF cap, to isolate Q1, then measure the voltages again?