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I've extracted a relay labeled OEG OL-C-212H12VDC from an early 90s Technics amplifier whose service manual refers to as RSY0009-0. It has an additional line indicating 9142 T. Its coil is busted, thus I cannot measure its resistance. From the circuit it was used in, it is a DPST and judging by its profile it is likely a reed relay. It has 20x8x6mm (LxWxH) and 6 pins. The label suggests its coil voltage to be 12VDC. Apart from that, I have not found any information about it. Clearly, I'm dealing with an obsolete part but I need to find an equivalent. It may not have the same footprint (I could do an adaptation) but it must have the same electrical characteristics (it is connected in series with other components).

Does anyone have any information (at least the coil resistance) about this relay?

OEG OL-C-212H12VDC relay

Edit: I added the reduced circuit in which this relay (K1) resides. Calculation gives a roughly 700 Ohm coil resistance.

Reduced circuit

Game Instance
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  • Do you have context of the circuit driving the coil? It may be possible to infer a coil resistance, or at least a range of acceptable coil resistances, if the circuit were known. – nanofarad Mar 03 '23 at 20:55
  • The relay in question is powered from a 62V rail and is connected in series with a 6.8Ohm current limiting resistor, a 3V zener diode in series (limiting the voltage for an indicator LED), 2 other relays with 1.1KOhm each (both in series). There is a 2.7kOhm resistor in parallel with it. My best guess, should it have a 12VDC coil, is that it has around 700Ohm. I'd rather be sure. – Game Instance Mar 03 '23 at 21:08
  • Your reasoning seems sound, from a quick calculation on my end (if I understood your textual description correctly; you may want to add it in schematic form). With that said, I don't know this relay firsthand, so I can't confirm that this is indeed the correct rating, beyond doing the same estimation you did. – nanofarad Mar 03 '23 at 21:13

2 Answers2

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OEG, aka "Original" if memory serves (ironically, perhaps), was a 2nd tier Japanese manufacturer. I believe the similar part number at TE Connectivity P&B is the exact same part, based on the Japanese surnames on the drawing.

All very interesting I'm sure, but there are no indications of coil resistance on the drawing so that's of little help to you. I am very confident the coil voltage is 12V and 700Ω seems reasonable so I suggest replacing the relay coil with a 700Ω resistor and testing the voltage across it with the relay energized. If you want to be cautious you can start with a higher resistance value, but relay coils are pretty robust and a few seconds won't typically hurt anything. Especially since most of the voltage drop is across other things.

Your added information would seem to support the above conclusion. It is fortunate that R1 is in parallel so the circuit can be adapted to whatever substitute you can find. There are many small sealed telecom style relays that should work in this application.

Spehro Pefhany
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  • I already tried that (removed the relay and placed 2 resistors in parallel with R1, one having 2k2 and the other 2k, giving a strikingly similar equivalent) and was able to verify the function of the other relays. I was hoping for more info on this obsolete part, ideally to find a replacement matching the through-hole footprint. I guess I'd have to settle with what I have thus far + an adaptation. – Game Instance Mar 03 '23 at 23:20
  • I followed-up on your suggestion (OMR-C-212H,000) an landed on an interesting resource: https://www.datasheets360.com/part/detail/omr-c-212h-000/4446294418699072924/ . The datasheet on that page (from Tyco, also containing the OEG mark) provides an explanation on the naming, which pretty much corresponds with that of the obsolete part. However, that part seems to have a 1050 Ohm coil resistance. At this point I'm considering doing a surgical incision in the relay's plastic case hoping to be able to tap into both ends of the coil and measure it. – Game Instance Mar 04 '23 at 00:37
  • In the end it does not really matter what it was. You can adapt it to any suitable relay you can find, up to about 20mA coil current, simply by changing the resistor. Many <= 2A telecom style relays (except some stupidly expensive military types) fit that constraint and many have the 2 NO contacts you need. Or pick one that is about right resistance and save changing the resistor. Relays (in a benign environment) don't care much about +/-10% either way so you don't have to hit it on the nose. – Spehro Pefhany Mar 04 '23 at 01:44
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In case this may interest someone else, I eventually found a site containing the details I was after: https://www.sourcengine.com/part-info/OL-C-212H000-2142359629 . Footprint info is not available but the product image in the PDF document liked by it ( https://www.sourcengine.com/download-datasheet/OL-C-212H000-2142359629 ) confirms it is the obsolete part in question (and that's indeed a 700 Ohm coil).

In terms of replacements, the OMR series recommended by Spehro Pefhany is an alternative with the following comments:

  • has a bigger coil resistance and requires another parallel resistor;
  • has a different (THT) footprint and needs adaptation that will not be very elegant (building an small intermediary bridging PCB will have to be double-sided and will end-up being mounted higher due to the trough-hole soldering on both sides) if not impossible (considering that the OMR's footprint is slightly larger than the original).

Another approach would be using SMT equivalents, such as FTR-B3(GA012) or G6K(-2G). Both have higher resistance (need another parallel resistor) but the adaptation bridging PCB would be feasible (parts have half the footprint surface), could be single-sided and rest flush against the main circuit PCB. Though exaggerated, one could even 3D print a case to hide the adaptation PCB.

Game Instance
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