Scrambler trouble - Debug info here, help needed!

[rats_eyes]

I resisted posting this for a while, as there have been so many debug requests for these on here already. However, this is my first build from scratch and I just can't suss it out. Any help at all would be very gratefully received! My soldering is not bad, I've managed to mod some pedals and built from a kit before with no problems. My understanding of the underlying principles is very patchy, so I'm likely missing something that might be obvious to someone who knows what they're doing!

When bypassed, my clean signal is fine. When the effect is on, I get a very quiet clean signal. Blend control seems to turn the volume up and down, but there is no fuzz or octave at all. The transistors were all listed as ECB at the supplier, and are installed in the right position as far as I can tell. I've checked the positions of my capacitors and resistors and haven't yet found a problem. I can't see any shorts on the pcb either. Any ideas???

1.What does it do, not do, and sound like? Octave Fuzz
2.Name of the circuit = Ampeg Scrambler
3.Source of the circuit (URL of schematic or project) = Tonepad
4.Any modifications to the circuit?  N
5.Any parts substitutions? If yes, list them. No, used all 5 diodes, also used 2n5306 and bc169b
6.Positive ground to negative ground conversion? Y or N
7. out of circuit battery voltage? => 9.18

Now insert the battery into the clip. If your effect is wired so that a plug must be in the input or output jack to turn the battery power on, insert one end of a cord into that jack. Connect the negative/black meter lead to signal ground by clipping the negative/black lead to the outer sleeve of the input or output jack, whichever does not have a plug in it. With the negative lead on signal ground, measure the following:
Voltage at the circuit board end of the red battery lead = 9.16
Voltage at the circuit board end of the black battery lead = 0

Now, using the original schematic as a reference for which part is which (that is, which transistor is Q1, Q2, etc. and which IC is IC1, IC2, C1, and so on) measure and list the voltage on each pin of every transistor and IC. Just keep the black lead on ground, and touch the pointed end of the red probe to each one in turn. Report the voltages as follows:

Q1
C = 9.2
B = 1.0
E = 0.03

Q2
C= 3.2
B= 0.9
E= 0.3

Q3
C= 9.2
B= 3.7
E= 3.5

Q4
C= 8.8
B= 4.1
E= 3.5

D1
A (anode, the non-band end) = 4.2
K (cathode, the banded end) = 4.1

D2
A = 4.1
K = 3.2

D3
A = 4.1
K = 4.1

D4
A = 4.1
K = 4.1

D5
A = 0.3
K = 0.0

[Derringer]

C3 on that layout is backwards from how it should be. The "-" end of that 1uF cap should face the blend pot
also, I built mine using that layout but without D3, D4 and D5 ... so I don't know if having those in hurts or not

I don't know what the voltages should be, but yours seem to be reasonable
try flipping that cap

[PRR]

> Q1
> C = 9.2
>B = 1.0
>E = 0.03

There's a near-short to ground at Q1 Emitter.

Derringer is correct that C3 is laid-out backward, and would "act short", that's not the whole problem because C3 leads to 47K resistors.

> Q3
> C= 9.2
> B= 3.7
> E= 3.5
> D1
> A = 4.2
> K = 4.1

D1 Cathode is connected to Q3 Base. Why are they different voltages?

Did you buy the PCB from TonePad, or DIY it?

[rats_eyes]

Thanks for the replies! I forgot to mention that I have already reversed C3, after reading some of the tonepad build reports. Sorry about that.

The PCB is a DIY job, it seems ok at a glance, but I'll have a closer look, especially around Q1. I've noticed that if I wiggle the transistor gently in it's socket (all the transistors are socketed) the volume increases for a second. I can't hear any fuzz when this happens, just volume.

[rats_eyes]

I scraped around the copper tracks on the PCB and tidied up some solder joints, particularly around Q1 and it works, kind of. There's still something a bit loose, as it starts and stops working intermittently if you move any of the parts around (it's not all secured in an enclosure yet). I figure this might be my offboard wiring.

The pots seem to work in reverse aswell! I inverted the wiring on the pots, but this didn't work at all, so I put it back. The texture knob is doing very little, but the blend works reasonably well. The schematic on Tonepad doesn't really make the pots wiring clear to me, the lugs aren't numbered.

Hopefully this will be a bit more reliable after I've fixed some of the wiring. I was really pleased when it made the right sound, I wasn't sure if I'd get anywhere with this at all! Thanks for your advice so far folks.