How to bias a fuzz pedal after changing transistors?

[niblos]

I am kind of new to this sort of thing but here is my question: I recently ordered some Texas instrument cv7003 (military version of the oc44) and wanted to change just the fuzz side transistors on my 9-3700 Vox stereo fuzz wah. I wanted to try a germanium transistor for a warm, smoother fuzz tone. My question is how do I bias these two cv7003s? My friend says he can check them for leakage and that sort of thing. I have read a few things about bias control on DIY fuzz pedals but what about something minor such as exchanging transistors? Is there anything else that I need to consider? You help is greatly appreciated!

[petemoore]

Is there anything else that I need to consider?
A schematic.
Bias, you'll be able to tell much more about these transistors and the circuit with a schematic and some bias information, all the kinds of stuff that you know after the fact.

[niblos]

I do have the schematic for the vox stereo fuzz wah (9-3700) as well as the vox distortion booster (V8162) that was actually the very same circuit found in the fuzz/wah. However I don't have anyway to post them. I will be happy to send them to anyone who emails me at the following:
jcook27@nc.rr.com

[petemoore]

  That's a Fuzz Face type circuit.
  2Q feedback loop, high gain stage, NPN/Negative ground.
  Perfbread it.
  Stick sockets for Q's, put a 4k7 + 10k trimpot for Q2 collector resistor, 4k7 through 14k7 is a good range to stick to to adjust the circuit bias.
  Adjust the pot and 4k7 to = the measured value of the 10k in your old circuit.
  Try transistor combinations using the schematic [or better yet the values measured on the original].
  Then adjust bias to determine if 10k is the optimal value for Q2.
  I like to 'center' the bias according to temperature, starting at say 60 degrees?, then warming the transistors [with a soft slow pinch] to the high temperature test, measuring bias and listening for tonal changes...'centering' the bias appropriately for likely conditions.
 

[niblos]

Man Pete - I cannot thank you enough!  You really know your stuff.  I'll have to show this to my circuit buddy, maybe this is exactly what I've been looking.

http://s612.photobucket.com/albums/tt20 ... uzzwah.jpg

http://s612.photobucket.com/albums/tt20 ... uitasf.jpg

[petemoore]

  Ge FF's...throw one together and try to determine if you got lucky.
  I used to race them, build and use two of them BTB on the pedalboard, then tweek one...constantly figureing out what modifications were 'still' improvements when I had time to actually use them for enough time to find out what they do under the many varying circumstances which widely vary the ''FF sound'' [which is a whole plethora of various tones from clean, treblyboost clean, od, distortion, fuzz...
  Mainly I go for not quite topped off gain, and ability to clean up at the guitar volume control pot, which may include altering that pot too.

[niblos]

OUCH! That is WAAAY over my head. I had no idea it would be so involved just for a couple of transistors. I really appreciate your help and you have really giving me some great advice where to start. I think it may be just as simple to build a few pedals to get some hands-on experience before jumping into such a project. Since it is a vintage piece I think I'll just keep it stock. The characteristics aren't that bad and kind of has it's own sound.

You have made me even more appreciative of builders like Analogman Mike and Paul Cochran. I cannot thank you enough for taking the time to answer all my questions and then some. You are simply amazing. It's great to see all the free information on this site.

Keep up the superb work and let me get to work!

Take care and may GOD bless,
Robbie