Custom Fuzzface Debugging Help

[rocket8810]

Once again, after some smooth sailing on some builds, I get one that I can't figure out what is wrong, so I seek a other eyes and experience in solving my issue.

The bypass signal is fine, but when the pedal is engaged there is only white noise/hiss. What makes this more interesting to me is that the volume control works, and I can't essentially increase or decrease the volume, but not input signal can go through. Should make note that I did wiring this for a battery and dc jack, which makes me thing that could be causing an issue.

I checked the tracks and couldn't find any bridges, checked the layout and it looks right, so I'm stumped. I know it had to be something stupid I did since it happened to me before on a different build which I just put aside cause I couldn't figure it out.

I haven't made a pedal with a DC jack and battery snap in awhile so I thought that might be the problem. I swapped out the stereo jack and battery snap for a mono jack and just the DC jack, and some of the white noise/hiss stopped, but it's still there and I can't get any output. Here's the layout I'm working on. It's a modified Creepy Fingers Fuzzface, with added tone control and bias pot.

Here's the layout


Basic Si Fuzz Face Schematic



I don't have a schematic for the fuzz face part, but it's based on the creepy fingers fuzzface, which as far as I can tell there's an additional cap between, q1 and q2.

The bias pot doesn't seem to alter the bias of the transistor. Here are the voltages for the transistors below, I have 9V coming in.

Q1                            Q2                             Q3
E 8.94V                      C 9.46V                      C 9.31V
C 9.47V                      B 0V                           B 0V
B 9.47V                      E 0V                           E 0V

Note: I have a 2n5088 transistor in the booster section.

Here's the board I built, based on the layout.









I'm really lost on this one. Much appreciate the help.

[dwmorrin]

Looks like the layout has errors.

Appears to me that you've connected the first two transistor's collectors together.
Q1's collector should run into Q2's base.

You'll have to redo the layout.
Or just twist Q2's base and collector legs around?

[rocket8810]

Thanks dwmorrin. I took a look at the layout, but as far as I know the fuzz face section should be correct. It's based on this layout for just the Creepy Fingers Fuzz Face which is verified and I've built it and works.



which is based on the p2p turretboard layout from turrentboard.org (R.I.P.)

Someone I know who has made a few layouts for me before added the tone section with a recovery booster. The other thing is I could just take the layout above, put a bias pot in place of the 8.2k resistor, then run that to a daughter board that has the tone control recovery booster, but I was hoping to have it all on one board.

I've had a similar situation happen to me before, where I don't get any output except white noise/static that can be raised and lowered with the volume pot. What else could it be?

[dwmorrin]

Looking at your voltages,
Q1's collector should be dead equal to Q2's base.
They are connected, or should be.
Your voltages indicate those terminals aren't connected.
The two collectors are at the same voltage.

So either you reported the wrong voltages, or you've got to twist your legs around.
Double check the pinouts.

Hmm. Since the schematic Q1 emitter is at 0V, and your Q2 emitter is at 0V, then perhaps you recorded the voltages backwards for those 2?

Q#s and pinouts on your layout would help to avoid confusion.

[Davelectro]

Layout says both transistors are BC130 but I see two different pinouts showing.  

[LucifersTrip]

the problem is a bit deaper than that

Q1                            Q2                           
                            C 9.46V       
C 9.47V                                         
B 9.47V   

The above voltages basically mean those points are shorted (all connected), which they shouldn't be. 

[rocket8810]

the problem is a bit deaper than that

Q1                            Q2                           
                            C 9.46V       
C 9.47V                                         
B 9.47V   

The above voltages basically mean those points are shorted (all connected), which they shouldn't be. 

Ok Lucifer, I just checked the pinouts, and the transistors are in correctly, and checked to see if there is some connection between all those points, but according to my fluke, on the "beep" setting there isn't continuity between these points. Maybe I tested the voltages wrong or somehow the metal tops were touching causing the connectivity? I had the ground attached to the box, and used the positive lead to test each leg of the transistor.  When I did it again, using the same method I got the following:

Q1                            Q2                             Q3
E 0.668V                    C 1.092V                     C 9.31V
C 9.50V                      B 0.564V                     B 0V
B 1.098V                     E 0V                           E 0V

When I removed the transistors this is the voltage readings:
Q1                            Q2                             Q3
E 0V                          C 9.47V                      C 9.31V
C 9.50V                      B 8.92V                      B 0V
B 4.97V                      E 0V                           E 0V

Still no change in the pedal, I get no output when the pedal is engaged.

Dave, there are two different pinouts for the transistors, as the vero is made off of the turrentboard layout seen in the link below.
http://turretboard.knucklehead.dk/wp-content/uploads/2012/04/creepy_si_fuzz.pdf

[LucifersTrip]

ok, those voltages are closer to reality...but it's too difficult to work without a schematic and I'm not going to spend time tracing veros since I don't use them.

but, just to be clear, Q1 & Q2 is the fuzz face & Q3 is the boost?

here's a couple notes with only looking at the voltages

1) you know the first transistor in the FF has E grounded, so should be 0V. It doesn't look like either of the other two E's should be grounded (0V)

2) C's at close to supply voltage 9.5, 9.47, 9.3 are way too high...possibly won't even pass signal

[dwmorrin]

Voltages looking better.  I think you're still confusing Q1 and Q2, as far as recording the voltages go.

Bias pot not doing anything?  What value is it?  Check value on both Q1 and Q2.  I think you may be looking at the wrong collector.

Q3 will be cut off if the base is at 0V.
Looking at the vero, base just has 1M to ground, and the passive tone circuit connected to it.  You'll need another resistor from Q3 base to +9V to turn Q3 on.  Double check and/or post info about your extra tone stage.

[rocket8810]

Voltages looking better.  I think you're still confusing Q1 and Q2, as far as recording the voltages go.

Bias pot not doing anything?  What value is it?  Check value on both Q1 and Q2.  I think you may be looking at the wrong collector.

Q3 will be cut off if the base is at 0V.
Looking at the vero, base just has 1M to ground, and the passive tone circuit connected to it.  You'll need another resistor from Q3 base to +9V to turn Q3 on.  Double check and/or post info about your extra tone stage.

The bias pot is B10k, and the resistance changes when the pot is turned, but there is no change in the actual voltage that gets to the transistors. Double checking the layout with the general schematic for the fuzzface q1 is the first one on the left, then q2 has its E directly on the ground, then q3 is all the way on the right.

Checking the layout there is a 10k resistor from +9V to C of q3, and 220ohm from e to ground.

Lucifer, I'll have to draw up a schematic for this, as it was an idea I had and someone I know put together the layout, so I'm not really working off any schematic other than the creepy figers fuzzface.

[LucifersTrip]

Double checking the layout with the general schematic for the fuzzface q1 is the first one on the left, then q2 has its E directly on the ground, then q3 is all the way on the right

look again at the schematic you posted, then follow the input path (thru the 2.2uF) on the vero you posted and you'll see that Q1 is the one in the middle.

[rocket8810]

Double checking the layout with the general schematic for the fuzzface q1 is the first one on the left, then q2 has its E directly on the ground, then q3 is all the way on the right

look again at the schematic you posted, then follow the input path (thru the 2.2uF) on the vero you posted and you'll see that Q1 is the one in the middle.

My bad, you're right. I was looking at the 2.2uF as the 22uF by mistake. So the voltages for q1 and q2 should be switched. I just built it on 2 board which solved the output problem, so there has to be a problem in the layout, but now no matter what I do it won't bias. If you look at the creepyfingers fuzz layout, I replaced the 8k2 resistor with a b20k pot, even set it to 8.2k but still the bias not right.

[dwmorrin]

Re: bias of Q2,
It's possible you'll have to lower the 33k at Q2's base a little.
If you have alligator clips, try clipping in a 100k or a bit higher, in parallel with the 33k.
That way you can avoid desoldering in case it has no effect.

Double check that the path from Q2 emitter->10ohm->fuzz pot->ground.
Resistance check from Q2 emitter to ground should be "in the ballpark" of 1k, or whatever the value of your fuzz pot is.

Re: bias of Q3,
Not concerned with collector or emitter connections.
It's the BASE you've got to look at.
I just see a 1M to ground, and your voltage readings confirm this.
BJT transistor base needs at least 0.6V before it will turn on for you.
Where's the schematic for Q3?

[rocket8810]

Re: bias of Q2,
It's possible you'll have to lower the 33k at Q2's base a little.
If you have alligator clips, try clipping in a 100k or a bit higher, in parallel with the 33k.
That way you can avoid desoldering in case it has no effect.

I have to look for my alligator clips and try that. In trying to decrease the resistance I would assume that it should change the voltage going through q2, so what should the voltages be for q1 and q2?

Double check that the path from Q2 emitter->10ohm->fuzz pot->ground.
Resistance check from Q2 emitter to ground should be "in the ballpark" of 1k, or whatever the value of your fuzz pot is.

I checked this path and it does run from q2 emitter -> 10ohm -> Fuzz Lug 3 -> Fuzz Lug 1 to ground. Fuzz Pot is C1M, but when I check the resistance from q2 emitter to ground i get 800k, 0.800M on my meter.

Re: bias of Q3,
Not concerned with collector or emitter connections.
It's the BASE you've got to look at.
I just see a 1M to ground, and your voltage readings confirm this.
BJT transistor base needs at least 0.6V before it will turn on for you.
Where's the schematic for Q3?

I don't have a schematic for q3. What I did is just build the creepyfingers fuzz, run the output to daugherboard with a Big Muff Tonestack+LBP-1 booster, then ran that to the output of the pedal.

Basically this:


with Volume 2 as output into the input of this:


The only thing different that I did was I removed the 8k2 resistor and replaced it with a b20k pot. The new tone knob works correctly, the volume pot works correctly, when the fuzz knob changes the fuzz level, the bias knob changes the voltage at the collector at q2 from 9.50V to 9.45V, but it won't bias correctly. Its just nasty and gated sounding, and no signal from strings 5 & 6 unless plated with lower cords.

Even when the resistance is set to 8.2k it's just super gated and really nasty sounding. I've changed transistors, still have the same issue, so I checked the pinouts but they're right.

What can I do to get the bias right? Could there be something else wrong?

P.S. I'm working on making a schematic for both boards since it will help with diagnosing the circuits.

[dwmorrin]

I have to look for my alligator clips and try that. In trying to decrease the resistance I would assume that it should change the voltage going through q2, so what should the voltages be for q1 and q2?

Typically, the Q1 collector/Q2 base junction resides in the neighborhood of 1.2V, or 2 diode drops above ground.
The Q2 collector needs to be between 1V-9V to pass audio, and then you twiddle your 10k pot until you like it.
Currently, it seems you're stuck at 9V, which means your Q2 is OFF.  So, we need to figure out what is keeping it OFF, and then turn in ON.

I checked this path and it does run from q2 emitter -> 10ohm -> Fuzz Lug 3 -> Fuzz Lug 1 to ground. Fuzz Pot is C1M, but when I check the resistance from q2 emitter to ground i get 800k, 0.800M on my meter.

Did you "check the path" with eyeballs or meter?  Check that each connection shows near 0Ω resistance, and that the 10Ω is really 10Ω, and that the 1k pot is really 1k.
It's also possible you're simply mis-reading the meter, because 800Ω is probably OK.

If this path is wrong, then that's why Q2 is OFF.   If this path is right, then you may need to mess with the 33k.

with Volume 2 as output into the input of this:

Look at the base of the transistor here.  It's got 1M to +9, and 100k to ground.   Your circuit has 1M to ground and no +9 connection.

[rocket8810]

I did both a visual check and a check with my meter. With my meter at each connection I get near 0ohm resistance.

Rechecked the voltages with bias pot set to 8.2k:

q1                          q2
C 1.112V                 E 0.676V
B 0.578V                 C 9.48V
E 0V                        B 1.108V

This time I listed q1 and q2 correctly. Also, hfe of q1 is measured at ~350hfe , and q2 is measuring at ~650hfe.

Look at the base of the transistor here.  It's got 1M to +9, and 100k to ground.   Your circuit has 1M to ground and no +9 connection.

I see what you mean. I will make that change in the layout, but I'm not concerned about that layout now. As I said, I now have 2 separate boards, one with the fuzzface, one with the tonestack w/ booster.

I tried to make a schematic for both circuits. Hopefully they are right and will help.

Creepyfingers Fuzzface


Big Muff Tonestack w/LPB-1

[dwmorrin]

I corrected some errors on your creepy fingers schematic.  The changes are circled in red.
Small cap should be from Q1 collector to base.
Electrolytics are drawn backwards.
Fuzz pot is labeled 1M, should be 1k.
Forgot to circle, but note how Q1 and Q2 are connected.  You had collectors tied together.  Should be collector Q1 into base Q2.

[rocket8810]

hmm, on DIYLC the electrolytics are labled correctly, something most have happened when it was converted, but I see the mistake with the 39pf, can't believe I messed that up  . But, I checked the pedal, and I accidentally grabbed a C1M, not C1K pot. I'm going to switch it out for the right one tomorrow. Could that be part of the issue?

[dwmorrin]

But, I checked the pedal, and I accidentally grabbed a C1M, not C1K pot. I'm going to switch it out for the right one tomorrow. Could that be part of the issue?

YES.  That's why your meter reads 800k from emitter to ground, and why Q2 won't turn on.

[rocket8810]

But, I checked the pedal, and I accidentally grabbed a C1M, not C1K pot. I'm going to switch it out for the right one tomorrow. Could that be part of the issue?

YES.  That's why your meter reads 800k from emitter to ground, and why Q2 won't turn on.

Just changed the C1M for a C1K and the pedal works beautifully. Just went through my boxes and found that a few C1M pots slipped into the C1K section. Got to check what I grab. If I had then I wouldn't have had this headache. Thanks for all the help.