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SAMSUNG washing machine doesn't power up

I have a washing machine that has stopped in the middle of a cycle and showed an 'UC' error. On the SAMSUNG's site it says that is is related to the excessive fluctuation of the power supply voltage. I turned it off and now it doesn't turn on anymore.

Analyzing the main board, I've checked low voltage power supply and it seems to work, it outputs 37V (or something like that, I don't remember the exact value). On some connectors I've measured 5V and 12V.

In the same board there is also a relay connected to the input that, when active, powers other components (like the door lock) and the main rectifier circuit that powers the inverter.
If I bypass that, the machine turns on and after a couple of seconds I can hear the relay activating. At this point I can remove the bypass and the machine stays on. (I haven't tried to run a cycle)

At this point I'm not sure on what is the problem. The description of the error code makes me think that it has something that measures some kind of voltage? (I don't know what it checks and where), so maybe that is faulty? Or I'm missing something else?

I've attached a simplified schematic  that I've drawn while trying to understand how it works.

Block Image


Moreover, I've found a service manual online that have some details on the wirings: https://www.manualslib.com/manual/279727...

Do you have any suggestions? Thanks.

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@dennisloi what model is your washer?

da

@dennisloi Can you upload pictures of the circuit boards inside your washing machine?

da

@oldturkey03

@andrewsawesome

Sadly I don't have anymore access to the machine or the board, so for now is on "standby".

Anyway, the internal board is exactly the same as the service manual that I've linked.

I don't have any pictures of the board because they are covered in resin and is very difficult to take a good photo. But nothing seems blown or burned on the board.

I have done some more troubleshooting after the post, here's what I have found:

- I traced the power supply for the relay, the rail is not active because the enable pin of the regulator is off (my guess is that it's controlled by the microcontroller)

- There is a optocoupler that sense the AC voltage, the LED seems fine (I've measured a voltage drop of 1.3V), but I'm not sure about the output as was still covered in resin.

Anyway, I will update this post (or put a comment) when and if I will be able to continue working on it.

da

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It sounds like, from your troubleshooting, either K1 or what is driving it is bad.

Do you read a driving voltage on K1? If so, K1 is bad. If not, you must figure out what is driving it and what it senses to drive it.

Unfortunately, that isn't in the manual.

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Hi Bill, thank you for the answer. I'm not sure what's K1, is the voltage regulator that I've mentioned in my last comment? In that case the Enable pin was off and I successfully turned it on by forcing it high with a resistor.

As soon as I have time to take a look at it I will remove the heatsink to see if there is something that 'senses' the input voltages (apart from the optocoupler that I've mentioned before).

da

@dennisloi I believe K1 is the relay, the model number you provided is ADW11. You should check if the relay is getting the power it's supposed to. If the relay is getting the correct voltage and it's not latching, then the relay is bad.

da

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Dennis Loi sarà eternamente grato.
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