LRE Fuzz Sound ~ schematic, guts, troubleshooting, etc...

[LucifersTrip]

finally got around to opening up and troubleshooting my LRE Fuzz...

There's some pics here, but no guts:
http://www.effectsdatabase.com/model/lre/fuzzsound

so here are the green-tinged guts:

bottom of board:


top of board:


side1 of board:


side2 of board:


The analogguru schematic is 404, so if anyone saved it, please post.
http://analogguru.an.ohost.de/193/schematics/Mica_FT-12.gif

In the meantime, with the start of an incorrect schematic posted elsewhere, I've got this:


It's obviously a Maestro FZ-1A rip, but is more similar to another rip, The Fuzz King, which I built...and it sounded nothing like an FZ-1A. it was fatter, more like a Fuzz Face


For the LRE Fuzz, I got (EBC):

Q1 (-.73, -.78, -1.59)
Q2 (0, -.023, -1.52)
Q3 (0, -.011, -1.54)

...which are actually closer to the Fuzz King, but the sound samples online are more similar to the FZ-1A

since I was getting something within reason on Q3's collector, I expected some sound, but I got zilch. Since I was getting a bypassed sound, by process of deduction, the problem was  most likely somewhere after Q3....and it was. The volume pot is dead. It's open between the wiper and either side, though from left to right lug it measures 50K (just like the  FZ-1A).

With the bad pot still wired, I hooked an output jack directly to the output cap & got a very poorly biased, gated fuzz right off.
Does anyone know what the voltages should be? (-.6 to -.8 like the4 FZ-1A or -1.44 like the Fuzz King?)

Who sells a smooth shaft 50K (log or linear) with a simple on/off switch? It's a little less that 1" in diameter and the shaft is also a little shorter than 1". It's very similar to this:


Ironically, I actually put in a schematic request for the LRE Sound over a year ago...which I replied to myself now.
http://www.diystompboxes.com/smfforum/index.php?topic=87404.0

Any suggestions would be cool

thanx

[petemoore]

  Dunno, looks like new capacitors and new board at least would verify stuff-and-everything easier than probe to probe point through crusty traces like that...so a whole new build looks like it might make sense ?
   That board looks 'shot' to me.

[LucifersTrip]

 Dunno, looks like new capacitors and new board at least would verify stuff-and-everything easier than probe to probe point through crusty traces like that...so a whole new build looks like it might make sense ?
   That board looks 'shot' to me.

closeups do really make stuff look worse than it is. I actually verified almost all connections from leg to leg (I scratch off a small portion to get down to some shiny metal and use small hook clips). The only think I found bad was the pot....and of course, there's little chance of the transistors all being the right gains for this circuit.  my biggest wonder is weather Q3's collector should be around -.6-.8 or -1.4

I can always work around the transistors with some resistor adjusting.


thanx

[LucifersTrip]

Ok...I finished breadboarding and tweaking this thing and it turns out it is (of course) set up similarly to the FZ-1A or Fuzz-a-Tort (same fuzz control)

I won't go through all the details of my tweaking, but simply:

Q1: If you use something leaky or with low gain, the fuzz will be dirtier and lower volume. I actually wound up with a much higher gain one than I would've expected. The lower gain ones simply didn't give me the smoother, saturated fuzz I got from the 2SA221 (hfe 200, leakage 175uA)

Q2: this was the hardest one to choose. If you use a leaky one here, it basically nullifies the fuzz control. I threw a leaky one in here and it was like the fuzz was full all the time. the fuzz control had virtually no effect. I tried all different gains & leakages until I got a good sweep on the fuzz control. I wound up with a 2SB165 (hfe 100, leakage 100uA), but I could not choose Q2 until I had a correct Q3.

Q3: I started with a transistor with leakage ~ 100-200uA. the collector voltage was -1.55v and the fuzz control was useless. I got a semi-gated dirty fuzz and the the fuzz control was only useful in the last 10%. the first 90% was very low volume and dull and the high E was super gated.  it wasn't until I threw in the 2SB376 (yes, also my savior for Q3 on the  Burns Buzzaround...hfe 70, leakage 300+ uA) that this came to life. Immediately, Q3's collector voltage dropped to -.7, the fuzz was loud, smooth, killer with good sustain & decay and the fuzz control had a good sweep, but was even better after taking the time to choose Q2.

A couple notes...according to Small Bear (Fuzz E-One tweaking), I'm right on the money for Q1's emitter voltage, -.6.

SB recommends -1v on Q2's collector. I could go as high as -1.15v, but the best fuzz was somewhere in the -.75v to -.90v range. I set it to -.85v by changing the 10K off of Q2's collector to 5.1K

Once Q2's collector was set to -.85v, I set Q3's collector to ~ 1/2 supply. It actually sounds decent all the way from -.3v to -1.1v, but indeed ~1/2 supply was the best.

Everything is killer, except for one flaw. The circuit only works well with a leaky Q3, but with the leakage comes the typical hiss ("shhhhhhhhhhhhhhhhhhhh...") of a leaky transistor.  I can cut down on some shhhhhhhhh... with a 200uF cap across Q3 B-C and completely remove it with a 500uF cap, but there is sacrifice to the fuzz quality. I got the same shhhhhhhhh... with all leaky ones I used and different Q1's and Q2's didn't solve the problem either.

Is it a catch 22 or is there a solution?

final version (so far):