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yeah i remember discharging with a screwdriver too . them days there were no sensitive electronics though, shorting capacitors that way these days with microchips in the circuit could possibly blow up the silicon chips or other sensitive components on the board though

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  • 2 weeks later...

Hi Everyone,

Just registered here, lots of great information so thanks for that.

I have a question and was wondering if someone could offer some advice? I have a wdx8543130w washing machine that completly died. I replaced The D7 Diode with a Schottky 100v 2a replacement (STPS2H100).

The machine worked again without issue after replacing this for about 12 hours and 1 full wash but I just had a message from my wife saying it's dead again and won't power at all, so the same issue as before.

I could potentially just replace that part again but since I don't want to be doing this daily, is there a possible cause for these failures that I could fix? Maybe another faulty component somewhere causing this diode to fail?

Any advice would be really appreciated.

Thanks,
Alex

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On 13/09/2023 at 16:28, ajsaxon said:

Hi Everyone,

Just registered here, lots of great information so thanks for that.

I have a question and was wondering if someone could offer some advice? I have a wdx8543130w washing machine that completly died. I replaced The D7 Diode with a Schottky 100v 2a replacement (STPS2H100).

The machine worked again without issue after replacing this for about 12 hours and 1 full wash but I just had a message from my wife saying it's dead again and won't power at all, so the same issue as before.

I could potentially just replace that part again but since I don't want to be doing this daily, is there a possible cause for these failures that I could fix? Maybe another faulty component somewhere causing this diode to fail?

Any advice would be really appreciated.

Thanks,
Alex

Switch mode power supplies can be tricky to fix, one failed component could kill another, and if you suspect that the transformer is faulty you probably won't be able to source a replacement. Also, the large capacitors can still retain a charge for some time after the device is unplugged, the ones on the 240v side will charge up to in excess of 300 volts, so allow plenty of time for the capacitors to discharge before touching the board.

Only thing I can suggest is to inspect your soldering on the new diode to make sure you don't have a dry joint, and if you have a meter, test the new diode in circuit to confirm if it is the same fault. I would also suggest inspecting the board to see if any of the electrolytic capacitors have a bulging top, or bottom, or have leaked electrolyte (sure signs of failure), and also look for discoloured and scorched components. 

You'd then need to start testing the individual components you can with a meter to see if they are in spec, and removing those that can't be tested in circuit.

My electronics knowledge is negligible at best, so I've no idea what would cause that diode to fail repeatedly, might be a good question to ask on an electronic forum. At a wild guess, possibly it could have been caused by excessively high reverse voltage spikes from the transformer, but even if it was, I've no idea what would cause it to suddenly start doing that.

One of the more common components to fail in SMPS are the electrolytic capacitors, and they all slowly lose capacitance over time due to evaporating electrolyte (cheap brands are worse), but I doubt a failing cap would cause that diode to fail, I would expect failing capacitors to make the output voltages unstable and cause the washing machine controller to hang, or crash, or the smps control chip to shut down repeatedly.

 

Edited by MelS
typo
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Another success with the replacement diode D7, this time on a Beko WDIX7523000 washer dryer. Hopefully the repair will last but a massive thanks to Bob12241 for his brilliant instructions anyway. The machine has had very little use but is, of course, out of warranty. Once again, a couple of quid spent instead of £79 for a new PCB. What a result!

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