Need help with weird-behaving self-built Fuzz Face

[Joecool85]

I think you might have the polarity on the caps backwards.

[Fret Wire]

Built on perf, right? Have you checked your solder joints with a good magnifying glass for cold or bridged joints? I'd give that a try, plus it wouldn't hurt to re-flow all the solder joints either.

[Speeddemon]

I think you might have the polarity on the caps backwards.

No, I did that one time on accident when I replaced the 22uF with a 15uF (because the 15uF doesn't have a minus-symbol, but a narrowing of the enclosure, while the plus-side has a black stripe, so I figured that would be the minus-side) and then there's a very faint, ugly signal, which is totally different from what I'm experiencing when I got the caps right.

@FW; I did check them several times and I also made sure to go through 'alleyways' with a knife, between solder-'heeps', so that 2 different things couldn't connect.

I'm getting a PCB after X-mas I think, so I'll transfer all the parts to that, see if it matters. But I'm really at a point that I could toss the whole thing out the window. 

[Joecool85]

Thats what happened with mine.  I was ticked.  I grabbed a new board, soldered it all in, and it worked!  I think I had a short somewhere on mine I was overlooking.  Something to think about.

[b_rogers]

wait a minute you said q1's collector was 4.5 volts? did you mean q2? if its the first transistor, check to make sure the resistor going to q1's collector is indeed the value specified, check it with your meter. q1's collector should be like 1v or slightly higher. coudnt hurt anyways...

hope this helps

Brent

[cmat]

I had a weird problem like this.  The pedal worked normally and then the voltages would start rising on the tranistors untill the pedal wouldnt work.  It turned out I hadnt hooked up a ground wire to one of my pots   It has been working eversince 

[Speeddemon]

I had a weird problem like this.  The pedal worked normally and then the voltages would start rising on the tranistors untill the pedal wouldnt work.  It turned out I hadnt hooked up a ground wire to one of my pots :-[  It has been working eversince 

Right now I have 2 seperate ground wires from the board to the pots and from the volume pot to the 9V input jack.

@b_rogers:
Yeah I ment Q2. While Q2 was rising from 4,5V upwards, Q1 was dropping from 0,438V downwards. I haven't checked the 2 AC141's properly for leakage, but the problem was the same with different (silicium) transistors as well. 

[Joecool85]

Do those two ground wires connect?  They should.

[petemoore]

  I'd like to see a chosen schematic, and transistor type [npn/pnp].
  Also complete pin voltage information [EBC readings from both Q's].
  And battery supply measured voltage to reference the pin voltages by.

[Speeddemon]

  I'd like to see a chosen schematic, and transistor type [npn/pnp].
  Also complete pin voltage information [EBC readings from both Q's].
  And battery supply measured voltage to reference the pin voltages by.

Hi, I based it on the schematic posted on http://fuzzcentral.tripod.com/fuzzface.html

transistor type = NPN
Batt. supply voltage = 9.32V

[petemoore]

Also complete pin voltage information [EBC readings from both Q's].
From ground, take a voltage measurement with DMM from Q1 Emitter, base and collector, also Q2's Emitter, base and collector, post them here.
  NPN Neg Gnd FF schematic...
  They are probaly 'normal npn's, so looking at the top of the board with input to the left/output to the right... the emitters would be on the 'bottom', bases in the middle, and collectors nearest V+, the transistor markings would be facing the output...or verify pinouts to board connections by inspecting the board connections, comparing them to the schematic, also transistor data sheet.
   transistor mis-pinout
is a common miswire for FF's....something to recheck at least. 

[Speeddemon]

Hey Pete, the PCB's arrived, so I immediately populated them and threw one into the enclosure.
It WORKS!
And what a tone too. With my Burny Les Paul Custom (Randy Rhoads model), GFS Vintage '59 Alnico PAF neck and GFS Crunchy PAF bridge, I pretty much nailed the Guess Who-"American Woman" tone (both lead and rhythm).
I put 2 N3904's in there (hFE around 240-250) and with the fuzz control (1k lineair) maxed, it has this saturated, singing, violin/fuzz tone.

HOWEVER... Is it normal for a Fuzz Face circuit to have the biggest change in fuzz intensity in the last quarter of the 1k lineair potmeter?
Or should I try 1k log or 1k reverse log?

Also, with some guitars, the fuzz had a sort of switch-point, when you roll back the volume. Below it's crunchy overdrive and above it hits into the fuzz. It's not gradually. But, when you put a buffered pedal in front of it (off), that problem is gone.
Any idea if that behaviour is normal?

Or is there a treshold voltage that the N3904's need?

[b_rogers]

the "switch point" you refer to is pretty normal. with the FF's i have made the transistion is more gradual with strats than humbucker guitars. germanium cleans up better, but silicon to my ears sounds better. the pot bunch up at the end is also normal, i usually omit the pot and just use a 1k resistor to ground and the guitar vol becomes the pot (sort of) Fuzz faces rule! altho i admit i like mine best into a ts style circuit. try the multi face at runoff groove for hours of fuzz tweaking.

enjoy!

[petemoore]

  Small Bear sells the wierd taper 1k Fuzzpot for the circuit, makes it very evenly ranged to dial in the Gain. I add a small stop resistor [100 ohm or better] to match the gain I want for that one, if it needs it.
  Maybe a resistor at the input, or input gain control would change the way your guit's volknob works, tame the FF a bit, maybe even keep some noises out.
  Sounds like you're using different pickups, you can put the input gain mod on a switch or use a pot.

[Speeddemon]

Hey Pete, where would you place the resistor then? Before or after the 2.2uF electrolytic?
And the value? Something like 1 or 2 Mega Ohm?

[petemoore]

 Small Bear sells the wierd taper 1k Fuzzpot for the circuit, makes it very evenly ranged to dial in the Gain. I add a small stop resistor [100 ohm or better] to match the gain I want for that one, if it needs it.
  "Pete, where would you place the resistor then".
  If you check out Joe Davissons FF calc, you'll see that FF's can use tweeking of the gain pot value. This bears out in practice, too large [2k2?...5k?], starts messing with the bias and sound too much, I decided it's worth it to just 'set' the value of the gain resistor [or pot].
  a 2k2 pot produces more gain than a 1k, so...setting the pot to a 'middle-er] position also puts resistance between the 22uf and feedback loop [100k].
  I used to start with a 2k2 adjusted fully Cw [max] and 'work down' the value [actually using another pot, 5k or so, clipped across the 2k2's outer lugs], set max gain at 'whatever'...not oversaturated, just a touch more than you'd use...depending about pickups etc.
  Measure the removed/undisturbed setting you liked on the 5k, replace with same value fixed resistor where the 5k was used to find the value across the 2k.
  Now, since I have access to the 'correct' pot from SB, I insert an R value between the gain pot and ground to increase max gain to where I want it. Starting with the SB 1k FF pot, Fully Cw, but splicing a 1k lin. pot between the SB gainpot and ground, setting max gain, and replacing the 'R value finder' pot with a fixed resistor of nearest same value, maybe having to build the fixed R value from resistors [to more closely match the target value.
  "I'm calling it 'floating' the pot...[stop resistor is the term tho] min. gain will be 'bumped up' as will max gain. ...the gain range adjustment is 'moved up' by the gain bumping resistor, between the gain pot and ground....something between 100 ohm and 1k, or to taste.
  This might not be necessary for Si or some FF's, A 1k gainpot might even be more than you want.