Hello. I’m trying to identify a part that’s cracked/broken. It’s a 4.5mm diameter x 2mm wide circular disk with two legs. Color is green or maybe blue. It belongs on a radio antenna control board for a BMW E30 from 1989. The brand/make of the antenna is Hirschman 6000EL. I do not have a schematic for the control board. Thanks!
Are there any markings on the board that are not shown in the image?
Would the item have any markings on it?
Hi Nathan, no, no real markings that I can see. I took a closeup of the part taken off the board. The first image was from a board on ebay since I thought it would be more clear as my board suffered some heat damage and everything is darkened up quite a bit.
Sadly without knowing more about that item we would really not be able to offer anything or narrow down to any general group of items.
Sorry.
If you can find out what type of item that would be we may be able to do more.
Possibly an MOV or thermistor. Without part markings or a schematic however, there’s really not enough to run with. Beyond that, there’s apparent damage to a number of other adjacent components and PCB traces. Best bet would probably be to look for a replacement module.
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@rick_1976 Yes, something definitely went terribly awry on that little board. I’ve tested several of the other components and they seem to be testing ok. I agree a replacement board would be best but I’d like to try to fix this one just to learn more about repairing electronics. I think I maybe can repair the traces.
I looked up MOV’s and that is definitely what it looks like; the top right image at this site, with the legs on the sides of the disk looks correct! Also, from what I read, an MOV would serve to protect the circuit so maybe that’s why it took the bulk of the damage?
I don’t mind buying several different parts to try out. Do you have any thoughts on options I could try? I totally understand it would be a guess and not even a remote hint of a solid recommendation.
Do you think this guy would be worth a shot in the dark?
https://www.digikey.com/en/products/detail/nte-electronics-inc/NTE1V010/11644426
Based on appearance and design vintage of early 1980s, I think its’ a disc type thermistor for inrush current limiting or temperature compensation.
@PaulHutch Hmm, very interesting. I agree one of the keys is the 1980’s design around 12V automotive systems. I looked up some thermistors; if this is what we have, I’d likely need an NTC thermistor? I followed the trace of the “thermistor” and it goes to a transistor similar to this one. Looking at the specs of that transistor, I think I’d want to be around 500mW for the thermistor? I’m not sure what resistance I’d need but maybe a thermistor 33ohm like this would work?
https://www.digikey.com/en/products/detail/epcos-tdk-electronics/B57164K0330K000/652178
I remember reading tech articles on automotive circuit design where they used thermistors in those ways as a hobbyist in the 70’s and then for work in the 80’s. However I never ended up needing to use them that way in any of my designs, so I can’t remember any operational details, I just remember how they physically looked.
Hi Paul, Did you end up fixing the circuit board? I have the same board except the MOV is discolored. If I want to replace it, can you let me know which part I need and it’s valve?
Thank you