Mark III is kicking my but

[jzam]

I have been breadboarding some mark 3 variation schems of the fuzz central site.  I am having trouble getting the transistor voltages where they should be.  It make some sound when you hit the strings hard but that's all it does. 
right now I got
Q1 c 1.80
     b 1.78
     e 1.71
Q2  c 1.82
      b 1.71
      e 1.80
Q3  c .20
      b .12
      e 0.0
battery is a good 9+ volts  HFE is 50 60 70. 2sb's   I tried some higher 70, 70 120hfe  with no major change.
I didn't think this was real picky as for as transistors.  Any thoughts.
thanks

[LucifersTrip]

I have been breadboarding some mark 3 variation schems of the fuzz central site.  I am having trouble getting the transistor voltages where they should be.  It make some sound when you hit the strings hard but that's all it does.  
right now I got
Q1 c 1.80
    b 1.78
    e 1.71
Q2  c 1.82
     b 1.71
     e 1.80
Q3  c .20
     b .12
     e 0.0
battery is a good 9+ volts  HFE is 50 60 70. 2sb's   I tried some higher 70, 70 120hfe  with no major change.
I didn't think this was real picky as for as transistors.  Any thoughts.
thanks

since you have reasonable transistor hfe's and the voltages are so far off, there's a high probability of a mis-wiring or short.

post a clear closeup pic of your breadboard and maybe someone will find the error. Also, tell us exactly the transistor #'s you are using along with the schematic.

[Ripdivot]

is it possible the transistors are in backwards?

[Quackzed]

is that a tonebender mkiii? fuzzes are all a bit picky about their collector resistors...maybee try changing em to get the collector voltages close to where you want em. or sub in a trimmer for the collector resistor and dial it in...
or just look up 'fuzz face biasing'. i think the tonebender is basically a fuzz face with an extra transistor stage in front of it...
oops looks like the mkiii has an extra stage AFTER the 'fuzz face part'... the resistors that may need adjusting are the 680k and the 10 k above q2 <--- this last one is what i'd try first... try 20k and if its a bit better you can experiment from there, if its worse, try 8k or sometihng a bit lower...also that 680k try a 470k or even a 220k and see if that helps, tho the 'intended sound' of the circuit may depend on this resistor being 680k...

[skrunk]

the MkIII is nothing like a fuzz face, the first 2 trannys form a darlington pair.
you're right that it isn't too picky about transistors, the gains you have should work fine, I'd go for the 120hfe in Q3 though.
I suspect you've set the circuit up wrong somewhere or have one or more of the trannys in the wrong way.
you're voltages should measure in minus volts as it's a positive ground circuit, yours are positive.
with the stock circuit, you shouldn't have to go messing about with biasing to get a decent sound.
also make sure the ge diode is the right way round.

you could use these voltages as a rough guide:

q1
c  -3.8v
b  -1.6v
e  -1.5v

q2
c  -3.8v
b  -1.5v
e  -1.4v

q3
c  -3.5v
b  -0.04v
e   0v (ground)

note that the collector voltages of Q1 and Q2 should be the same and the voltage at  Q1E should equal Q2B.
Q3's collector could measure anywhere from -1.5v to -5v for a decent sound.

[Quackzed]

oops, my bad! 
your right, i took a quick glance and had it in my head from a mkii i had built that the first 2 transistors were in a fuzzface arrangement...
they are indeed set up as a darlington pair. sorry bout that! 
a common issue with positive ground pedals is confusion about battery orientation and wheather the grounds go to - batt etc...
i'll refer to all the ground symbol points as 'ground' here.
if you wire it up as if it was a normal -(negative) ground pedal,you have to keep in mind the electro caps orientation (+ side to 'ground', opposite of normal orientation), you then just have to be sure to hook up the battery + terminal to  'ground' or rather to the input jack ring, which will connect it to 'ground' when a mono cable is used.
so theres a few things to remember... in a positive 'ground' pedal.
1. all electro caps oriented + side to 'ground'.
2. battery + terminal connected to input ring. (which will connect to 'ground' when a mono cable is used.)
3. battery - terminal connected to negative side of that 22uf cap as well as the top side of that 220k and the juction of the 2 10k resistors... the top left line in the schem...

[jzam]

Alright it works!  I cant believe I had the battery connected backwards.  I was going off a boutique bender wiring diagram that showed black going to the input and red going to board though it had the - + live and learn.  Any way I pretty much nailed shrunks voltages accept for q3 c is -1.5
It sounds good like it is but I would like to see what it sounds like at 3-4v also. Maybe I should try a trim pot next.  BTW I am using 2sb415's leakage around 130ua for all 3. 

I also tried some alternative resistors ala park fuzz here http://fuzzcentral.ssguitar.com/3knob.php

FYI this is what I got for voltages using the park fuzz schem
Q1 c-4.92
     b-1.11
     e-1.07
Q2 c-4.92
     b-1.07
     e-.99   
Q3 c1.48
     b-.05
     e -0

[Electric Warrior]

Different gains and leakages can make quite a difference for q3 in my experience. It sure is worth messing with. Keep swapping transistors until you find out what you like best 

[Quackzed]

 

[jzam]

I have been messing around and by removing the 10k to ground on Q3 this jumped up the C voltage to -4.92 and lots of volume.  The boutique bender schem has this left off also.    I also tried a 10k in place of the 18k and this up the C voltage to -2.24. 
It will definitely be one to play around with.