Help debugging TS 808 please...

[adam_f]

Hey, I'm having problems locating the problem with my TS808 (using Torchy's veroboard layout).

1. I'm not getting any distortion sound, it just lets the normal signal through, although the volume is a little quieter than in bypass. The gain and tone controls have no affect, but the volume control works. At max volume it is  quieter than bypass. and it goes down to nothing.

2.Name of the circuit = Tubescreamer TS808

3.Source: http://www.indyguitarist.com/torchy/Distortion_Overdrive/Tubescreamer/screamer.GIF

4.Any modifications to the circuit? None

5.Any parts substitutions? I used a 47pf cap instead of the 51pf one cos I couldn't find one.

6.Positive ground to negative ground conversion? N

7.

Voltage at the circuit board end of the red battery lead = 9.02
Voltage at the circuit board end of the black battery lead = 0

(using dc power supply as I only have one battery (for my multimeter!) but it does the same thing with a battery.

IC1 (4558 chip):

P1= 4.94
P2= 4.63
P3= 4.52
P4= 0
P5= 4.89
P6= 4.91
P7= 4.9
P8= 9.02

Q1 (2N3904):

C= 9.02
B= 1.57
E= 1.11

Q2 (2N3904):

C= 9.02
B= 1.57
E= 1.11

D1:

A=  0
K= 9.02

D2:

A= 4.6
K=4.93

D3:

A=  4.93
K= 4.6

D4:

A= 4.95
K= 5.29

Any help would be much appreciated,

Thanks a lot,

Adam

[R.G.]

Hi, Adam.

This is similar to a problem another fellow was having. The low voltage on the base of both transistors is suspiciously like a transistor pinout problem. Can you recheck the pinout of your transistors and where they're connected?

[adam_f]

hey, I checked that and it was right. Then I realised the problem...one of the holes undeneath my chip wasn't scratched out properly! It was a tiny amount of copper on the stripboard, but it was conducting. Got rid of that and it sounds awesome!
I'm having one slight problem though. When plugged in next to my morely wah it makes quite a lot of noise. I think it's probably mains hum coming from the ac adaptor, but I'm not sure what to do to get rid of it. funnily enough it gets quieter when the TS808 is further down the chain, and when there is no wah it's very quiet.
Any ideas?

Cheers,

Adam

[R.G.]

Good work!

On the hum, what is the connection like and what's powered by what?