What are the proper voltages for a Fuzz Face? And resistor problem.

[azrael]

I'm trying to bias a '69 Fuzz Face clone I built. It's kind of lame, because I bought the transistor for Small bear, and I lost the paper that tells you what transistors to use. So I'm kind of lost there.

Anyway, my voltages are WAY off. Anyone know what the real ones are? Mine seem to be, on all the transistors legs, around 3.7V when the trimpot is maxed.

And a bunch of the resistors I use are either way off from their tolerance, or are not reading at all, when I try to use my multimeter. Weird. Anyone know why? Normal carbon film ones.

[azrael]

anyone?

[George Giblet]

Sounds like you have a wiring problem or you have put the transistors in wrong.

You should end-up with voltages like this,

http://homepage.ntlworld.com/s.castledine/greenfuz/fface.html

For biasing you should try to get about 4.8V on the collector of the second transistor.

[hellwood]

I'm trying to bias a '69 Fuzz Face clone I built. It's kind of lame, because I bought the transistor for Small bear, and I lost the paper that tells you what transistors to use. So I'm kind of lost there.

you need to check the Hfe on your transistors and put the lower value as Q1 and use a trimpot to bias Q2's collector. once you get the collector to read 4.5, yank the trimpot, measure it, and hunt down the resistor small bear sent that is the closest to that value.

Anyway, my voltages are WAY off. Anyone know what the real ones are? Mine seem to be, on all the transistors legs, around 3.7V when the trimpot is maxed.

mine are:
Q1 c -.487, b -.119, e 0      (Hfe71)
Q2 c 4.33, b -.487, e -.373 (Hfe128)
are you using PNP or NPN and are you sure you know your pinouts on those transistors?

And a bunch of the resistors I use are either way off from their tolerance, or are not reading at all, when I try to use my multimeter. Weird. Anyone know why? Normal carbon film ones.

are you measuring them out of the circuit? does your multimeter autorange?

[mac]

mine are:
Q1 c -.487, b -.119, e 0      (Hfe71)
Q2 c 4.33, b -.487, e -.373 (Hfe128)

A perfect FF

IMHO, Q1 should be set between 0.5v - 0.6v Ge, 1.2v -1.3v Si.

mac

[hellwood]

mine are:
Q1 c -.487, b -.119, e 0      (Hfe71)
Q2 c 4.33, b -.487, e -.373 (Hfe128)

A perfect FF

IMHO, Q1 should be set between 0.5v - 0.6v Ge, 1.2v -1.3v Si.

mac

yeah, you are right! its kind of annoying because this was my first pedal and every pedal since has been exactly Q1 - .5 and Q2 - 4.5.  I literally tried 50 different transistors on the breadboard before i committed to solder. I knew nothing about biasing. I was afraid of trimpots or any unknowns toasting my germaniums. I already had the specific carbon comp resistors that the schematic called for and was too impatient and excited to dial it in further. I was just happy the thing worked!!  I know better now! oh well, Q1 is only off by .013 and Q2 by .17.

[mac]

I like to set Vc2 to 4.3v in Si versions. It sounds a little more "ge" IMHO.

mac

[Dragonfly]

I like to set Vc2 to 4.3v in Si versions. It sounds a little more "ge" IMHO.

mac

Shhhh... !!!

Hush now !!!

[azrael]

Okay, I built the germanium transistor gain tester as per R.G. Keen's instructions. Works great! Closest I could get for the 2.472k resistor was around 2.46, but it gives me a general idea of where I'm at, with gains.

Q1 - around 140 hFe
Q2 - around 180 hFe.

Pretty high.


Also, I forgot to mention that I have a germanium diode (1N34A) in the circuit, reverse biased to the base-emitter junction on Q1, as per Plate-to-Plate suggestions. Is it possible that I fried the diode, and that's messing with the circuit?

[hellwood]

Q1 - around 140 hFe
Q2 - around 180 hFe.[/b]

Pretty high.

I have a germanium diode (1N34A) in the circuit, reverse biased to the base-emitter junction on Q1, as per Plate-to-Plate suggestions. Is it possible that I fried the diode, and that's messing with the circuit?

base-emitter junction on Q1??
i dont think thats the way its done. what schematics are you using?

if Q1's emitter isnt grounded, thats your problem (or at least one of them). make sure your fuzz pot is grounded as well.

[azrael]

I'm using a heavily modified layout from GGG, with Fuller mods and stuff, so it's like a '69.

And I'm pretty sure it's supposed to be base-emitter:
http://www.geocities.com/sunsetstrip/studio/2987/britface.html

There's the article. I haven't touched the fuzz yet and done anything with it, I'm a little frustrated with it.


EDIT: Oh wow! The emitter ISN'T grounded. The PCB trace isn't connected. I'll fix that tonight, and see what happens.

[hellwood]

base-emitter junction on Q1??
what schematics are you using?

OK, i see what you are trying to do.

EDIT: Oh wow! The emitter ISN'T grounded. The PCB trace isn't connected. I'll fix that tonight, and see what happens.

cool, im sure you will get positive results!