Help Identify Opto-isolator / Opto-coupler

[Whoops]

Hello,
I might need to replace an Opto Isolator,
it's from a Maxon CP101 vintage compressor pedal for guitar.

The only thing written is "81", it's a bit bigger than the Vactrol optos.

do you have any idea of what brand and model could it be?
pic attached

Thanks

 

[gyraf]

LDR's very, very rarely fails.

If the opto is really defective (have you checked?) chances are it's the led. Which is MUCH easier to replace than the LDR.

Other than that, many stompbox-forums are reverseengineering stuff like this.

Jakob E.

 

[L´Andratté]

Sorry no clue on the optoisoator, but indeed the ldr is the critical part and it is most unlikely to be damaged, the ( if broken) led colour can be identified by the forward voltage drop. So in the worst case you could salvage the ldr and couple it with a similar led
EDIT: if the led´s broken you can´t measure the voltage drop, if it ain´t you don´t need to,  :

 

[Whoops]

Thank you Jakob and Adratte,
I measured the LED forward voltage drop of 1.818V, so the LED seems fine.
I will power the circuit and measure the resistor.

I've seen similar Optoisolators (same physical size and looks) in old gear, who was making these kind of optoisolators before Vactec amd Silonex?

Thanks

 

[L´Andratté]

Clairex and Hamamatsu were manufacturers, but in old devices there´s also sometimes custom components like in the famous Countryman Phase Shifter, who therefore some claim to be uncloneable ;D

 

[gyraf]

EC&G, Perkin-Elmer, Raytheon and Clairex to name a few more.

Very hard to know exactly what you have at hand.

Jakob E.

 

[analogguru]

The optocoupler is a MCD735 from Moririca Electronics.

 

[Whoops]

The optocoupler is a MCD735 from Moririca Electronics.

Thanks analogguru and thank you all for the replies.

By the way how do you know is that exact model?
I can't seem to find much info on the Moririca MCD735 so I just hope everything is fine with the optocoupler and that the problem resisdes elsewhere in the circuit, and that I never need to replace it.

This is the info I was able to find,
pdf attached.

 

[Whoops]

Also this: