Identify this component....

[Pete66]

Hi

I need to identify this part in an ADA preamp.  On the schematic it looks like some kind of optoisolator it is circled in yellow.  On the PCB it is just a 6 pin DIP with no markings.

Thanks

[WyverntekGameRepairs]

I may be wrong, but it looks like a dual photoresistor-based optoisolator (more recgonizeably called resistive optoisolators) - basically an optoisolator intended for analog signal useage. In theory it would change the resistance of the photoresistors based on the brightness of the LED inside (which would be determined by the input signal voltage level). The resistors' values are measured by the amps, by the looks of the schematic.
Also, according to the schematic, U3 is the same chip (or at least a chip with the same function as U5). If that one happens to have a part number, try searching for a datasheet.

You should try desoldering and taking a look at the underside of the package. Sometimes, manufacturers put the part numbers on the underside of the chip package (I've seen it quite a few times). If you find a part number, you can look it up and be able to verify my guess.

If you can't find a part number under it, try and run a simple test on it to see if it is a dual photoresistor opto. Apply power (1.5-2.5V) to the LED (pins 1 and 2), measuring the resistance between pins 4 and 5, as well as 5 and 6. If you get varying resistances depending on the voltage applied to the LED, then it is indeed an analog optoisolator that uses photoresistor technology instead of phototransistors.

[coromonadalix]

I would say the same thing

Never saw  double ones ...

Maybe something in theses families
http://m.szxinlei.com/Product/detail/l/cn/id/11.html

[David Hess]

It looks like a variable resistance optocoupler which uses a pair of photocells and LED to me.  Two photocells are used to allow linearization circuits for precision gain control.

[coromonadalix]

Maybe this one or similar,  they wrote 1 meg  in the schematic

https://www.alliedelec.com/m/d/ecb1ed91959ae54d97cf67f5103d9b2b.pdf

[WyverntekGameRepairs]

It looks like a variable resistance optocoupler which uses a pair of photocells and LED to me.  Two photocells are used to allow linearization circuits for precision gain control.

Sounds about right to me.

I suggest running the test anyways just to make sure.

[Pete66]

Yes I found out that the newer versions of the circuit use this one:
https://www.alliedelec.com/m/d/ecb1ed91959ae54d97cf67f5103d9b2b.pdf

So maybe I have an older version.  Also there are no markings on the top or bottom of these IC's