Help - trying to fix an old Ibanez CS-9 Chorus pedal

[andrecau]

Hello All,

I've recently grabbed an old Ibanez CS-9 off-ebay. It had a big burn signal on the pcb where one of the diodes is (the one that protects the circuit against polarity inversion). I could not figure which value it was, so I fitted an 4001 in.

Now the pedal works when it's on, but it produces no sound at all when it is in the bypass mode.

I know it's a bit of a weird symptom, as usually the problem is the opposite, people get sound when it's in bypass but no sound when it's switched on.

Any clues on what can be the problem?

[andrecau]

anyone?? 

[anchovie]

I know it's a bit of a weird symptom, as usually the problem is the opposite, people get sound when it's in bypass but no sound when it's switched on.

That's usually with true bypass pedals where the effect circuit simply doesn't work. The CS-9 uses FET switching and has a heck of a lot of components in the bypass path. All you can really do is see if anything else (component or PCB track) got damaged by the diode catching fire. Trace through with an audio probe if you can.

http://www.schematicheaven.com/effects/ibanez_cs9_stereochorus.pdf