What is it?

[Turbon]

Hi, I have searched a lot for information about this. Anyone here that have a clue?

An externally hosted image should be here but it was not working when we last tested it.

Regards

 

[arnyk]

What is known about the circuit that it is in?

What can be measured when it is in use?

 

[Turbon]

It's from the notch filter in my hm-250 distortion meter. There are a few of them.
Sorry to say that i haven't measured it yet. That have to wait another week.
I have got a few suggestions - optocoupler and reed relay.
Regards

 

[arnyk]

Optocouplers are natural components of auto-nulling distortion bridges.

One pair of terminals are a light bulb or LED, the other usually a CdS cell.

Relays, not so much.

Example: the schematic for the Heath 5258 downloadable here: Heathkit Schematic and Manual Archive | Vintage Radio Info

 

[Jay]

From internet:

CdS cell output photocoupler Classic
MCD5221

Useful for creating such as AGC circuit.

Resistance value between the output side of the CdS cell current flows to the input side of the LED changes. Where the output is resistance rather than a constant current is miso (relation between voltage and current is linear).

Some discontinued direction because photo coupler of CdS output is using harmful Cd (cadmium). There is for now no element to the same function without using harmful substances. Can be re-design the circuit from the root to the circuit without a photo coupler of CdS output but circuit becomes complicated.

 

[Turbon]

Thanks.

Definitely an photocoupler! The page in japanese (I presume) suggests (i presume) that the mcd5221 is used in VP7720. So I'll try to find the schematic for it 🙂.

VP-7720A ?????????? ?? ??3: 16mm??????:Taking color photo by 16mm camera such as Konan-16 and Kiev30

Regards

 

[Turbon]

There seem to be very little information on the mcd5221. I found a datasheet regarding other moririca optocouples in the mcd range. Well the ones in my DM is still working so for now I'll leave them as is.

Regards