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My washing machine stopped to work - the drum does not rotate anymore. After inspecting its electronic boards I found this:

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It seems there was a major electric arc on the bottom side of the PCB, and the current flowed through the two pins highlighted in blue.

The other areas of the bottom side of the PCB and the top side also look clean. I don't see any component damaged.

I'm going to test:

  • the inductor (HARTU 290071-51)
  • the capacitor (390 uF 400V)
  • the NTC (NTC 60 1120)
  • the relay (HF7FD)
  • the transformer (BSH 9000640724)

Since there are no burns on the component packages, what could have caused such a spark? Do you think it is worth trying to fix it?

Mark
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    Usually they are replace only for most people. An electronics repair shop might be able to repair. What did the connecting wires to those contacts look like? – crip659 Jun 05 '23 at 20:38
  • @crip659 of course an electronic shop might be able to repair, but this is not the question. The wires look good, the sheath is not melted. – Mark Jun 05 '23 at 20:40
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    This could have been a big surge, which probably means dead ICs or IGBTs. And it could have been a stuck phase leading to a burned trace, which probably also means dead ICs or IGBTs. You'll likely need to test the behavior in state to find the component level problem. I would check for obvious shorted transistors, obvious shorted outputs, then test the motor for a short and (assuming none) likely replace the board unless the earlier testing turned up something easy to fix. – KMJ Jun 05 '23 at 20:49
  • Is it possible something landed on top of the solder points causing a short? – crip659 Jun 05 '23 at 20:50
  • @KMJ replacing the board costs about half than a new washing machine. Hence, if it was something trivial, fine, otherwise it's not worth it. – Mark Jun 05 '23 at 20:52
  • @crip659 I don't think it is possible, given that the board was enclosed into a plastic box – Mark Jun 05 '23 at 20:53
  • These boards fail they are not designed to last a long time. We have had them fail on dishwashers and washing machines from cheap brands to expensive ones. It's worth replacing a few components, if its out of warranty. – Rohit Gupta Jun 05 '23 at 21:33
  • If it's a long shot (which it sounds like it is) I would check first for shorted transistors. – KMJ Jun 05 '23 at 22:15
  • Yes, it has 11 years old. This is the first failure, and the whole machine worked perceftly until few days ago... – Mark Jun 06 '23 at 08:25
  • Usually (not always) burned/discolored connector pins are indicative of a high resistance connection caused by pins not making good, low resistance contact, or high current. – SteveSh Jun 06 '23 at 15:20

2 Answers2

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Generally, if a PCB looks burned, that means one of the components mounted on it in that area failed and seriously overheated. If you are lucky, replacing that component or components, and making sure the burnt area neither broke traces nor created new current paths, may be enough to repair it. If the failure blew out other components, or was due to other components failing, this may be more complicated.

keshlam
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Judging by the discoloration on the plug connectors, and the uniform darkening across the anti-creepage cut-outs, I don't think it sparked/arced, it simply got (way) overheated. My money would be on a loose connector fitting. It could be bent, weak, or was just not firmly affixed/seated when initially connected.

All the components except the capacitors are fairly high-heat-tolerant. That's a common-mode choke btw, not an inductor. Maybe the relay or choke has enameled windings that could have smoked, but usually they can take quite a bit of abuse.

Test the relay with 12v and see if it clicks. Then measure the resistance across the NO/COM/NC pathways; should be well under 1 ohm (be sure to test the ohms of the meter leads shorted and subtract that). The cap looks ok (not swollen), but it looks like you'll have to remove it to test it to be sure. R2917 also looks suspect; test that in-situ.

If you find something bad, just replace it. The main thing I would do is squeeze the blade connector's sleeves so that they really grab the connector lugs this time; i think that was the root. If they arced, there would be pitting and soot on the top-side, instead of the uniform discoloration, likely cause by machining, anti-tarnish, or fingerprint oils smoking from heat.

dandavis
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