Identify Diode - Page 1
Forum section: electronics / projects

author: NivagSwerdna
author_rank: Super Contributor
timestamp: March 20, 2022, 12:28:58 pm
content: My chicken coop door opener has failed and it seems that one (or both) of the diodes near the power supply (4xAAs) has failed.The PCB is covered in some conformal coating or silicon type stuff which I have tried to peel back.D2 definitely has a physical problem, it has a big crack, D4 also looks like it might be cracked.I think these are likely to be simple protection diodes for the two possible supplies but they are quite exotic.They are glass and have a blue band. Does that make them zeners? would a zener be used as a protection diode?Thanks in advance

author: NivagSwerdna
author_rank: Super Contributor
timestamp: March 20, 2022, 12:35:36 pm
content: With my cheap multimeter set to diode mode...0.2V when the black lead is near the blue band and the red it is at the other endOpen circuit the other way around

author: magic
author_rank: Super Contributor
timestamp: March 20, 2022, 12:39:33 pm
content: That could be Schottky.I have seen diodes with color bands but never knew what those mean.See if you can figure out how they are connected. Then it will likely become obvious what they are meant to do.

author: moffy
author_rank: Super Contributor
timestamp: March 20, 2022, 12:41:01 pm
content: If the 0.2V is correct, and the diode junction is undamaged, they are either germanium or Schottky diodes.

author: NivagSwerdna
author_rank: Super Contributor
timestamp: March 20, 2022, 12:50:46 pm
content: close up of working one

author: inse
author_rank: Super Contributor
timestamp: March 20, 2022, 03:42:50 pm
content: 0.2V is a reasonable value for a schottky diode.1N5819 comes to my mind if your current draw is not exceeding 1A.Package name is DO-213, the colour band is for polarity marking (cathode).Decoupling of supplies makes sense.If you only use one, you could swap it or even bridge it (at own risk).

author: Vovk_Z
author_rank: Super Contributor
timestamp: March 20, 2022, 03:46:38 pm
content: Usually actual SMD MELF glass small signal (or other) Shottky diodes are red plus black ring.The only one with a blue ring I managed to google is TMMBAT48FILM, or BAS85.xxxBut there are similar Zener diodes exist too.

author: Kleinstein
author_rank: Super Contributor
timestamp: March 20, 2022, 04:25:31 pm
content: The circuit does not look too complicated. So a rought reverse engeniering should be possible and tell what the diodes are good for.I don't think there are any SMD germanium diodes. So the main question is if a Zener, normal or maybe a zener.The color rings are not unique and one may find different diodes with essentially the same ring.

author: NivagSwerdna
author_rank: Super Contributor
timestamp: March 20, 2022, 06:09:20 pm
content: I replaced the two diodes with some PMEG6010CEH which were the first ones I found in my parts... probably not an ideal swap but it seems to work and the unit is back in the shed.

author: NivagSwerdna
author_rank: Super Contributor
timestamp: March 21, 2022, 11:13:26 am
content: The original manufacturer kindly confirmed the part was TMBYV 10-40So I think my repair should be OKSpecial Right to Repair thanks to service @ AXT-Electronic GmbH

author: moffy
author_rank: Super Contributor
timestamp: March 21, 2022, 11:19:33 am
content: Nice.