Shin-ei 8tr Fuzz/Wah debug

[Hotstuff]

So I found one of these in the trash a little while ago. Obviously it didn't work but I've got it running again but there's still something wrong. I did a search but I only found threads about the FY-2, but nothing about the FW-8. On this http://members.fortunecity.com/uzzfay/jax1/jaxfw.html page you can find all the info about the pedal.

What I replaced:
- both foot-switches
- the volume and the fuzz adj pots
- All the 10uF caps

After soldering the whole thing back together the sound that the Fuzz made was cool but still a bit strange, the attack is real slow. I have to strum really hard to minimize this effect.
I found on the debugging page that I should measure the volume on each transistor with problems like these. Here's the transistor layout + results:

Q1:
E = 0,12
C = 5,97
B = 0,71

Q2:
E = 0,44
C = 4,37
B = 1,09

Q3:
E = 5,33
C = 8,80
B = 5,97

Q4:
E = 1,20
C = 1,25
B = 1,88

Q5:
E = 1,20
C = 1,25
B = 1,55

Q6:
E = 2,85
C = 8,79
B = 3,35

Q7:
E = 0,08
C = 4,65
B = 0,69

Q8:
E = 2,75
C = 6,06
B = 3,35

Note that the the Base and the Collector are swapped on these transistors...
My guess is something is wrong around transistor number 4 and 5. That's as far as I got. Thanks in advance to whomever can help me.

Emiel

I forgot to say that when I turn the fuzz adj up the sound disappears like a volume pedal. This might be related to the problem...

[Sir H C]

Yep 4 and 5, looks like a short from emitter to collector.

[Hotstuff]

Okay so I replaced the two transistors just to see what effect it would have. Too bad cause it didn't help much. The fuzz is great but there's still a sort of threshold in there. I don't think there are any cracks in the print and the solder joints look okay. The original pots on the pedal  where 50K ohm - B according to the scheme. The pots I have on it now are 50K ohm - A. Is this a problem?

To clarify the last big in my previous post. When I turn the Fuzz Adj to the side coming from the circuit, as apposed to the one coming from the volume pot, I lose my sound.

Anyone else have an idea what the problem could be?

Thanks,

E

[Sir H C]

Looking again, Q4 is the problem.  Something around that part of the circuit.  If you notice, Q4 and Q5 should be biased identically, so the base, collector and emitter voltages should be the same without a signal.  Q4 has a much higher base voltage which is causing the collector to come slamming down hard.  This gives the gated effect.  I would say either the base to ground resistor here is bad, the cap to the base is bad, or the resistor to V+ is wrong.

First shot.

[Hotstuff]

Excelent! it was the base to ground resistor. Replaced it and the gated sound has left with the bad resistor. Thanks!

Though still I have a problem with the Fuzz adj pot. I know that the pot isnt bad. When I set the pot to the channel that is grounded I basically get no sound, as if I have two volume pedals. I know the pot is connected right and even though its only connected to the ground I should still get fuzz. Most likely from a weaker fuzz channel? I think there's a short in there somewhere... anyone know what it could be? 

Thanks,

E