Help with 1970s Guyatone Moving Box Flanger - SAD1024

[clarisso11]

did you find what's shorting out the emitter of the transistor?

I just found the damaged part! It was the tantalum C22 after all: no signs of damage and tested with low ESR, but continuity (0ohm) across the pins! Should have tested for a short like you suggested. I suppose I learned that it's not always enough to test capacitors with an ESR meter, and tantalums can fail with no visible damage at all.

Many thanks for your help x-pro, I no longer have 0ohm between DC rail and ground. I will start putting parts back, checking overheating and voltage along the way. Hopefully the SAD1024 is still working.. Will update on this

[clarisso11]

The pedal is alive again! Somehow the SAD1024 survived the whole ordeal. Replaced all the opamps just in case, and all is working great - can confirm the BC237 works well as a replacement for Q1 in this circuit.

Thanks to everyone who helped out with this!

[Helmholtz]

I just found the damaged part! It was the tantalum C22 after all: no signs of damage and tested with low ESR, but continuity (0ohm) across the pins!

For an ESR meter there's no difference between a short and zero ESR.