Electro-Harmonix Electric Mistress Repair

[Helmholtz]

[QUOTE=clarisso11;n929713
Based on those voltages and the symptoms, can we conclude that the SAD1024 is undamaged[/QUOTE]

Frankly, I have no idea how a partial damage of that chip coul/would show. Maybe ask Ralf Metzger.

[clarisso11]

Frankly, I have no idea how a partial damage of that chip coul/would show. Maybe ask Ralf Metzger.

Good idea, will do!

[clarisso11]

A little update:

After double-checking the DC jack continuity to ground, I re-installed it, and connected white and red wires again - no short this time!
But the effect still didn't sound right, it kept cutting out. I checked the electrolytic caps, and replaced two that showed high ESR and had drifted from the original values (the 10uf and 33uf), but still no luck.

Finally, I decided to check the trimpots. After marking the original position, and played with the Bias, I got the effect back! The effect sounds great, so the SAD1024 chip was undamaged after all.

One issue remains:
The pedal is noisy, as expected, but it has one layer of unexpected noise: A regular thumping, changing regularity with the rate settings. From what I have read so far, this might be VCO ticking, rather than LFO, and might require repair.

Before I go on a wild goose chase, could it be one of the remaining, original capacitors? I'm reluctant to just go and swap capacitors out, since the traces are quite fragile. Adjusting the trimpots doesn't change the thumping noise, and the noise seems to be louder with weak batteries.