LG Dishwasher Controller Board EBR73739203 worth repairing?

Thread Starter

HardTimes

Joined Mar 29, 2020
5
A dishwasher that appeared to have stopped halfway though its cycle in the night greeted me this morning, showing 1:37 remaining on the panel, completely unresponsive to front panel buttons. Breaker off and back on led to no display or response to button presses whatsoever.

This is LG model LDS5540BB. I opened the cover and found line voltage at the main PCB, so the separate noise filter inline between main PCB and mains power is fine. The 220uF cap circled in the attached photo was very clearly bad, not only bulging but actually open at the top. The 6a fuse near the line input was also blown - also circled in the photo. Note the photo is not mine, it's of a good board advertised online.

I've ordered another board but will be waiting until Thursday for it. I'm considering ordering and replacing both of the 220uF caps at the bottom of the photo along with the fuse just to see if I can get this control running again. My question is, is it worth bothering with? If the bad cap could explain the blown fuse, great, it might be worth fooling around with. If there is likely to be other components that are also bad, I don't have the skill or time to diagnose.

Could the fuse be blown because of just the bad cap? I can't test the bulging cap for continuity - I stupidly wound up destroying it getting it off of the board because of the potting compound.
 

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LesJones

Joined Jan 8, 2017
2,726
I would make a wild guess that the bridge rectifier has failed connecting AC to the capacitor from your description of the failed capacitor. I suggest testing the bridge rectifier as a first step. If it is worth repairing depends on how good you are at repairing switch mode power supplies and how much time you are prepared to spend reverse engineering it if the schematic is not available.

Les.
 

Thread Starter

HardTimes

Joined Mar 29, 2020
5
Ah, fair enough. So it is fairly likely that something beyond what's visibly damaged is bad - and it's in some really tenacious potting compound so I think I'm going to just cut my losses and let it go.... I know what a bridge rectifier is but wouldn't even know where to start trying to identify its components on this board....
 

MrChips

Joined Oct 2, 2009
22,067
If you are technically inclined and have access to parts why not try and fix it first?
That is what I would be doing.
 

Dodgydave

Joined Jun 22, 2012
9,637
What you have there is a Transformerless psu feeding a Switchmode on the right silver heatsink, ( yellow transformer) chances are that has gone and taken the bridge rectifier out too.
 

Thread Starter

HardTimes

Joined Mar 29, 2020
5
Ouch - now I'm wondering what the chances are that this took out components beyond this board - like the user interface - button board and display board, any sensors beyond the board... Guess I'll find out - these actually do have an ok-ish diagnostic mode...
 

Thread Starter

HardTimes

Joined Mar 29, 2020
5
Just posting again in case anyone finds this thread in a search....

Sorry, my sense of adventure got up and went, and I bought another board and now an entirely new dishwasher. The second control board made it through about a cycle and a half before failing similarly. Obviously there is something else wrong in the machine that's overloading and blowing these boards. I'm fairly sure the wash motor runs on possibly modulated DC coming off of the board - like many LG appliances this has "Direct Drive - Inverter" proudly embossed on the front. Is it possible the motor is drawing too much current and blowing these boards... Next step would be replacing the motor but I'm not sure enough what's happening to throw another $300-$400 in parts at it - bought a nice Bosch to replace it.
 

Thread Starter

HardTimes

Joined Mar 29, 2020
5
Can you check the 8 pin IC, above the relay. This is on the left side of the board. The 8 pin IC, may only have 7 pins/legs.
It could be an 'Offline regulator'. The link is an example only.
https://www.onsemi.com/pub/Collateral/NCP1070-D.PDF
Good luck, keep us informed.
For what it's worth - Here are the numbers on that chip: A6059H SK392 16356D - it does in fact only have 7 pins as you noted.
 
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