[sdiy] Non-DIY, but looking for repair advice...

[John Ames]

On Mon, 13 May 2024 01:57:44 +0000
Mike Bryant <mbryant at futurehorizons.com> wrote:

> First of all measure the voltages on the output op-amp power rails.
> If they are reasonable, look at the op-amp itself.  The highly
> attenuated signal could be it passing from a previous stage through
> the feedback resistor to the output.  Op-amps reject PSU hum really
> well, but not when they are dead.

By "the op-amp" here, I assume you're meaning the the VCA at the final
stage of the signal chain? I'll check that, but it's one of those
proprietary Yamaha chips, so if that's dead it's gonna be an adventure
getting it replaced :/

(For the purposes of this discussion, I might as well drop a link to
the service manual - the VCF/VCA stages are diagrammed on page 9.)
https://elektrotanya.com/yamaha_cs-5_synthesizer_sm.pdf/download.html