Anyone seen circuit modules like this before?

RE: Anyone seen circuit modules like this before?

fco2martinez — Mon, 11 May 2020 01:10:50 GMT

Those designs were done in the 80s for analog circuits were passive circuits were required such as resonant circuits or coupling filters, quick examples were: Chroma Delay line for Color Television and Dolby B or C for Compact Tape systems.

RE: Anyone seen circuit modules like this before?

frostybeard — Sat, 09 May 2020 09:13:59 GMT

I am going to venture a guess that it is a photomultiplier tube or Geiger counter voltage source. These output around 700 V, so that explains why it would be potted.

It could also potentially be an avalanche photodiode bias source, which outputs around 70 V.

There used to be a company in Salo, Finland with that logo that is on the module: Aspocomp

RE: Anyone seen circuit modules like this before?

arclight — Mon, 27 Apr 2020 16:20:01 GMT

As everyone else has said, these are "hybrid" integrated circuits. We used to see them all the time in car stereos, VCRs and HiFi equipment of that era. I think a common application were critical circuits that required tuning - they could be factory-made to a high quality standard, then dropped on to a low-cost "punch and crunch" through hole board assembly of much lower quality.

RE: Anyone seen circuit modules like this before?

Jan Cumps — Fri, 03 Apr 2020 21:39:46 GMT

Blue silicone potting compound. Some references:

https://www.eletimes.com/conformal-coatings-vs-potting-compounds-better-protect-pcb-coating-resin

https://wendy-rl.en.made-in-china.com/product/HvUmYnOJYcWs/China-Producing-Electronic-Potting-Compound-Silicone-Rubber.h…

RE: Anyone seen circuit modules like this before?

michaelkellett — Fri, 03 Apr 2020 20:20:57 GMT

They look like what we used to call "thick film hybrids". These were ceramic substrates with track and resistors printed on and fired. Then some normal parts were surface mounted on top. They were a good halfway house between through hole pcb (which was prevalent at the time) and custom chips. The advent of current surface mount technology has pretty much done away with them. The NRE charges are much higher than for surface mount on FR4 but for some applications they are still a viable approach.

RE: Anyone seen circuit modules like this before?

Fred27 — Fri, 03 Apr 2020 19:47:12 GMT

I've seen similar modules in more recent electronics. This is a photo of the inside of my Tado (v1.0) thermostat from about 2010. I believe it was a either a DC/DC convertor or switch mode power supply under that blue coating. I can't remember which.