dead tube screamer

[Shack]

my TS9 is a 90s model with a maxon board and the wrong op-amp in it, but it hasnt worked in years.....id like to fix it rather than buy a new one.

I suspect the LED is shot, and im not sure if the switch is the issue or the LED......or the transistor bypass system...I put power to it and plugged a cable to the input, and have 9 volts at the anode of the LED, and my signal goes through the pedal, but doesnt change when I hit the switch.

I would love to mod it to an 808, but wont attempt it until I have it working. Does anyone have advice about what to do with this, id hate to throw a 100 dollar pedal in the trash if theres a chance I can bring it back to life, and my solid state electronics knowledge is limited.

[pompeiisneaks]

You can test the led with a diode mode tester on a DMM.  Also most op-amps have a block diagram that can help you test them, they behave a lot like a diode at rest and if you know which legs to test in the right order you can confirm if they're passing the diode test as well, if I recall. (I've seen a video on this, but don't recall when/how so I've never done it myself).  If you can rule out the diode, then it may be the op-amp anyway.  Usually good design puts the led in a separate path so that even if it is 'out' the circuit should work, but that may not be the case.

~Phil

[Ed_Chambley]

I would guess it is the switch.  I have never seen anything but the switch fail in these and I have seen a lit of these.  Try jumping the switch first.

[Shack]

yea, thats what ive suspected all along. so glad I didnt just throw it away years ago, thx guys