Fuzz Face trimmer/impedance control: Where in circuit?

[patrick398]

Set your meter to 20VDC range, black lead connects to ground somewhere, doesn't matter where. Red lead connects to the transistor collector

[thermionix]

Set to DC volts.  Oops, sorry, didn't see Patrick had already answered.

[Purplexi]

I'm not getting any reading at all...do I connect the battery?

[thermionix]

Yes, and if you need to insert a plug into the input jack to turn it on, do that too.

[Electric Warrior]

Also, measure the battery voltage and post it along with the voltages on the transistor leads. It's good style. 

[Purplexi]

So...I decided to keep the 2.2k/470 pots. I put an 18k where 8.2k would have been which yielded a 6.11v /9.6 batt at q2.  A 33k got me under 1.0v at q1. Sounding better, like amp distortion but still no heavy-duty fuzz yet. Hoping a 10-20k trimmer at 33k will get voltage corrected.

         
                Happy Holidays!

[Purplexi]

Update, I know this is so amateur, but I just discovered I had an unfinished connection. Apparently the measurements are way off and...it sounds pretty darn close. A little less output and this fuzz might be the real deal, finally. I'll get my readings together but so far, it(transistors) seem to want the 470ohm resistor at the collector/33k position(470, 1.5, 18k) is that possible?? I'm thinking be safe and install a 10k trimmer there to get dialed in. I will finish this Face and thread before Winter starts. Thanks for hanging with, I've learned a lot, and now I'm even swapping components out and starting to grasp readings!

[Electric Warrior]

What does Q1C actually measure then? Under 1V is to be expected with germanium unless gain and leakage are extremely low, but how far under 1V? In a Fuzz Face I would expect between -0.3 and -0.7V. Q2's collector voltage was in the right ballpark, but I don't know how much the mods have shifted the voltages on Q2.

[Purplexi]

As to the previous voltage at Q2: Because of the 2.2/470 pots, the newer 33k, 470ohm, 8.2k resistor line-up rendered the voltage numbers unrecognizable. I know I was still learning ohm/volt meter, but the use of the Mayer inspired 18k got me understandable readings and it sounding impressive. Next I'll get proper readings together for each transistor, all legs. Thanks again!

[Purplexi]

So here's the voltage readings, hopefully measured correctly. It lacks gain but the overall output, sustain, cleans, are very good. One more resistor swap to get it fuzzing again?
Currently:
2.2k
1.5k                                       
18k                                           

Q1------->>>HFE:85
                    leak:0.2ma             
C=1.13
B=1.02
E=0.12 
Q2------->>>HFE:133
                    leak:0.27ma                 
C=7.7
B=7.67
E=0.11

Batt=8.72

[j_flanders]

The collector of Q1 is directly connected to the base of Q2. See schematic below.
There's only a wire, pcb trace, solder or whatever between them.
As far as voltage goes it's the same point, so the voltage (to ground) should be identical.


Ballpark figures would be:
Q1:
C: -0,6V (same as Q2 B)
B: -0,2V
E: 0V

Q2:
C: -4,5V
B: -0,6 (same as Q1 C)
E: -0,5V

Most of yours are pretty far off, and the fact that you have different values for Q1C and Q2B means something went wrong. Either the connection or the measuring.

I'm in the same boat as you. I recently bought a reissue (early 2000's) red ge Dunlop fuzz face and have been checking voltages and testing different values for  resistors and biasing voltages.

Voltages on mine are pretty much like in this schematic:
https://www.electrosmash.com/images/tech/fuzz-face/fuzz-face-bias.jpg

[duck_arse]

hmmm, I'm not sure if I've paid enough attention to this thread, but, both your emitters are not at 0V. and they seem to both be at the same not 0V voltage. that might provide a clue as to a place to search.

[Purplexi]

 I wound up going with the Mayer mod since this thing already had Omeg pots 2.2k /470. Resistors 2.2k, 1k, 18k got it close, but ...not