Orpheum Fuzz circuit help

Started by Tremology, March 28, 2005, 02:54:56 PM

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Tremology

This fuzz is a great vintage ‘60s sounding fuzztone. A friend and I have been trying to figure out the circuit on and off for about five years. It only has 10 resistors and 10 capacitors, two switches, two jacks, two transistors (both germanium) and two pots (a tone and volume), and of course, a battery. At one time a cap, the red one, was changed. Our guess is that it was a film cap as the rest of them were. Not many parts in it but the trick seems to be that there is no apparent connection to ground!! And, we cannot get the transistors figured out. Either they are both NPN, both PNP, or one is NPN and the other is PNP. We tried to clone it but that only ended up only with the circuit smoking. We need your help desperately!! Can someone help us figure out and draw the schematic to this box?
Here is the best I could do.  The pictures are a little off, but I think it is close enough to see where everything goes.
Tremology

If the pics aren't posted, I can e-mail them to you.





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If it ain't broke, don't fix it...modify it!!

Tremology

Sorry folks I goofed. There are only 6 resistors and 6 capacitors. The germanium transistors are labeled GE 6638 003 and GE A4056 713.
Please e-mail me and I'll send you the pictures. I can't figure out how to post them right now.
Thanks!!
Tremology
If it ain't broke, don't fix it...modify it!!

petemoore

You want it fixed or figure it out totally?...
 Here's how I try to fix it.
 Test for non continuity between V+ and V- at battery clip, input jack with Mono plug in it.
 Add 9V.  Test the voltages of the transistors leads compared to ground.
 {Audio inject or] ...Thumbuzz your way from the output jack...you hear your thumb connected through a probe at output jack tip, amp on, follow through the signal path from the output toward the input, 'buzzing' all nodes in the SP.
Audio probe from the input toward the output.
You should have a good idea of where not to look for the problem after buzzing or injecting audio from output toward input, and audio probeing from input toward output.
  You'll need a good diagram to find the signal path...see below. Once diagrammed, check that all ground points are actually made....post schematic and the likely ground points suspects will probably be easily found.

 Just changing the ancient caps for nice higher quality New ones might do the trick on it
 Thean  Her's what I'd do...others have done this before so...
 Get what Is known down on a window...where you can read and amend ... do you have EXP Schematic ? or on paper.
 By looking at the top and bottom of the actual circuit board, the topology of the schematic should mostly be there...-minus the NPN's and PNP's...orientations...the circuit should have only a few unknowns to it, after being traced and drawn out.
 Then looking at the schematic, you will better be able to choose a course of action.
 If you Can see the bottom of the transistors, or get any data/info on them, you might be able to figure out the PNP/NPN/orientations of them.
 On all the Ge's I have, the 'arrow' points toward output > the base lead is offset foreward where the CBE leads come out of the body of the transistor, if you can see which way the 'arrow' is pointing...or even feel, using a solid core wire bent, you should be able to press this on two of the leads at a time, the two back leads will make a 'flatback', both  outside leads to center lead should make a wedge...creating a triangle outiline.
 Anyway there's some stuff to chew on...you might find it in there, chew carefully !!!
 I'm not sure how them caps work...whethere they can short out or whether they just 'cut'...if they make an insulator [pass no current etc.] simply 'tagging' a good cap across it would be a suitable cap check method...I think I read that mentioned...worth checking out.
 I'd be tempted to jsut get rid of those caps anyway...
 So now you should have a complete diagram of the board tracings, component values [where discernable..resistors hopefully anyway].
Convention creates following, following creates convention.