Tubescreamer debug

[Ell]

Hey,
My friend recently tried to make a second ts808 (he traded his first one for bass gear).

1. The bypassed signal works, but as soon as you hit the switch the sound is gone. The LED comes on though.

2. Ibanez Tubescreamer TS808

3.

4. He has made a modification, by putting a link which goes across D4. He built another TS808 a few months ago and accidently did it to that, and it still worked and he liked the sound, so he's done it to this version as well.

5. There are no part substitutions.

7. What is the out of circuit battery voltage? => 8.97
Voltage at the circuit board end of the red battery lead = 8.96
Voltage at the circuit board end of the black battery lead = 0.00


Q1
C = 8.95
B = 1.56
E = 1.13

Q2
C = 8.94
B = 1.57
E = 1.13

IC1
P1 = 4.58
P2 = 4.63
P3 = 4.43
P4 = 0.00
P5 = 4.72
P6 = 4.17
P7 = 8.24
P8 = 8.92


D1
A = 0.00
K = 8.92

D2
A = 4.62
K = 4.57

D3
A = 4.57
K = 4.62

D4
A = 4.53
K = 4.57

[Ell]

Is there anybody out there?

Thanks.

[oldrocker]

Two words “audio probe”.  Tracing the input signal is the best way to find where the problem is.

[MikeH]

Yeah, an audio probe will be your best bet on this one.  Your voltages look good, it's most likely that a component is placed incorrectly or you've got 2 strips bridged that shouldn't be, or you've missed a trace cut.

[R O Tiree]

I'm a tad concerned about the rate at which the battery voltage appeared to be dropping as you worked your way through the various pins. Is the battery getting warm when connected to the circuit? Measure the current the circut is drawing. If it's drawing a lot of current, then there is an almost-short in there.