TS-9 Open Ground

[nasman3188]

Hello diystompboxes!

I have a problem with a friend's TS-9. The pedal was modified by Analogman and worked wonderfully for some time. The pedal now produces no sound, neither on nor off. I found that no point on the board has +4.5V, and the line which should be carrying said voltage is connected somewhere to ground. After staring at the pedal for a few days, I haven't been able to find anything with my limited knowledge. Do any gurus have any suggestions for tracking down where the open ground might be?

[aron]

Do you get 9V? If not, look for a bad diode near the power supply. I would guess the polarity protection diode is bad.

[nasman3188]

I get 9 volts.. although I haven't checked everywhere. Using an audio probe I have signal up to the base of the first transistor.

http://www.freeinfosociety.com/electronics/schemview.php?id=1088

[petemoore]

  Debugging sticky thread is the read you need.
  Note the voltages on the opamp pins, measured from ground.
  Before applying power, be sure there are no shorts across + / - of the power supply.

[nasman3188]

My proper debugging help request...

There is about 1.3k ohms across the +/- of the battery clip... I know this should not be.

Effect passes no sound. Analogman "SRV" mod, includes ta75558p op amp.

Battery: +9.14

Battery Leads on board R/B:  +9.06/+0
         
Q1 2SC1815
C= 9.05
B= 0
E= 0

IC ta75558p
1= 8.17
2= 8.13
3= 0.01
4= 0
5= 9.04
6= 7.35
7= 7.35
8= 7.35

Q2 2SK30A
D= 0
S= 0
G= 0.03

Q3 2SK30A
D= 0
S= 0
G= 0.04

Q4 2SC1815
C= 0.56
B= 0.70
E= 1.12

Q5 2SC1815
C= 6.79
B= 0.70
E= 1.30

Q6 2SC1815
C= 0.81
B= 0.7
E= 1.32

Q7 2SC1815
C= 8.98
B= 0
E= 0

D1 polarity diode
A= 0
K= 8.98

D2
A= 8.09
K= 8.05

D3
A= 8.05
K= 8.09

D4
A= 0.02
K= 0.51

D5
A= 0.05
K= 6.16

D6
A= 0.54
K= 0.02

D7
A= 5.6
K= 7.4

thanks in advance....

[nasman3188]

And now for my noob "this is why this was an easy fix" post...

Focused too much on the circuit board, I didn't see that the level pot had come loose and was shorting on the tone pot...

[petemoore]

  Backwards of magic, then you didn't see it, now you do !
  Schizzamm !