OCP71 phototransistor uses

[Otbaudio]

Anybody know if these old Mullard OCP71's can be used as a vactrol or LDR for a tremolo/harmonic tremolo? And if not what their practical use is?

I've ended up with a few and I don't really know anything about them or what to do with them.

Thanks,

Oli

[anotherjim]

You can paint them over and use as straight transistors. That's reversing the procedure whereby an OC71 is made into an photo-transistor by scrapping the paint off its glass case. People did that all the time, much to Mullard's annoyance, since the OCP71 cost quite a bit more.

I can't think of any pedal that uses them, not even modern Si ones. It's probably too hard to get consistent results. That said, noise fans might get useful "broken circuit" effects if one were to make something like a fuzz face including one.