Hi Brach,
Thanks for your repply. I am glad my relatively lengthy descriptions help. It comes natural as my background is in engineering, but not in electrical engineering, mind you. So it happens that I started playing guitar late in life, as a hobbie, and now I am exploring pedal assembling and starting to read about pedal electronics and modification.
Since I have several SNL-32SR2A, I will find 4 of the most similar in the batch and give them a try. To simplify trying different optocouplers, I will remove the ones currently installed in the PCBs (main and stereo) and install sockets in their place.
Any thoughts or suggestions will be most welcomed.
Regards,
Carlos.