GE Refrigerator Motherboard Repair

Thread Starter

peterboxer

Joined Mar 24, 2020
6
Hello Everyone,

I have a side by side refrigerator, GE Model ESS25XGMB from around 2002. A while back it stopped cooling. I replaced the main control board (replacement part WR55X10942) and the fridge is back up and running.

I am trying to figure out what to do with the old board. Is it repairable, if so, what things should I look for, what tests can I do? I don’t see any obvious failures (burnt components, swollen caps, blown fuse etc.). A few pictures are attached.

Here are the tests I have done so far:
Removed the control board to test outside the fridge. Used a cheater cord to provide 120V AC at the terminals at the bottom of the board (J11, marked Line and J7-9 which is neutral) and checked voltage at J2 pin 3 to pin 8 – voltage constantly fluctuating around 9 to 10 V DC. Also checked J4 between pins 2 & 3 – same fluctuating voltage between 9 and 10 V DC. I believe it should be about 13V DC for both those tests.

The schematic and tech sheet found with the fridge is also attached.

If there is no easy way to diagnose/fix then I might just scavenge the board for parts, but first would like to try and fix – both as a learning project and to keep as a spare if the board goes out again.

Thanks for your help.
 

Attachments

wayneh

Joined Sep 9, 2010
16,398
Sometimes the people selling repaired/refurbished boards will pay a bit for your non-working board. That'd be my first choice but probably not an option for you.

Next choice would be to replace the electrolytic capacitors. It's not terribly expensive and you don't have to do any testing or diagnostic work. And even it is not the problem, it extends the life of the PCB if you do get it working.

Finally I'd look hard at all the relays. It's possible one wore out. Testing these in-circuit and under power would be ideal but is tricky to do safely.
 

Dodgydave

Joined Jun 22, 2012
9,207
From Pic 5187, the yellow Transformer and all components the right side are a Switchmode psu, with U1 fet as the main pulsing osc and opto coupler U10 as the voltage control, looks like there is only one output 13V.
 

Thread Starter

peterboxer

Joined Mar 24, 2020
6
Guys, thanks for the super quick responses!

@Dodgydave -- I do believe the problem must be in the SMPS since I'm not getting 13V. Are you saying the possible culprits are U1 and U10? If U10 is the voltage control is that the first one to try to replace (I'm assuming there is no easy way to test)? Also, I don't see anything labelled U1 -- is it the one with a heat sink, near U2 and U3? I think that's labelled D10 (a little hard to tell).

@wayneh -- the idea of selling it to a board repair place is interesting. How do I find one, do you have any names? It would be a last resort if I can't find any other option.

Thanks.
 

Thread Starter

peterboxer

Joined Mar 24, 2020
6
I did find U1 -- it is mounted on a heatsink to the left of the transformer, right where it says Warning High Voltage. It's a TOP246YN.

However, I cannot find any markings (part number) on U10. Can you help?

Also, what tests can I run -- e.g. what voltages can I check for on which pins on both U1 and U10? Would you have a schematic or block diagram for the SMPS?

Thanks.
 

Dodgydave

Joined Jun 22, 2012
9,207
TOP246YN is a Switchmode chip, U10 is an Opto-coupler that is used to feedback to the Top chip to set the output voltage, using a Zener diode and resistors, download the datasheet for the TOP246YN to see how it works,.
Here is an example circuit..



unnamed.jpg
 
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Thread Starter

peterboxer

Joined Mar 24, 2020
6
Thanks, that is very helpful. I will look through and then decide how to proceed. I assume the U10 opto-coupler on my board is the U2 (LTV817A) shown on the datasheet schematic? Since I cannot determine which IC has been used as U10, would an LTV817A be an appropriate substitute if I need to replace?

One more question, if you don't mind. As I understand it the 13V DC supplies are used to run the condensor and evaporator fans and provide power to the front control board. But, why would the compressor not work if the 13V is not present? Is there logic on the board to prevent the compressor from running if the fans cannot operate? Or could there be some further problems, even if I fix the SMPS?

Thanks.
 

narkeleptk

Joined Mar 11, 2019
465
Since you have a good working board a octopus tracer would be a useful tool for you in tracking down the fault. Down side tho you'd have to have your refrigerator down while doing the testing and comparing.
 

Thread Starter

peterboxer

Joined Mar 24, 2020
6
Well if the 13V is there then the Switchmode is working ok, and there must be a logic control signal to put the relay on/off that isn't working.
Well no, the 13V is not working. What I was wondering was if that was enough to prevent the compressor working, or if there could be other problems in the board (the compressor itself is OK, it works fine with the new board).
 

Thread Starter

peterboxer

Joined Mar 24, 2020
6
Since you have a good working board a octopus tracer would be a useful tool for you in tracking down the fault. Down side tho you'd have to have your refrigerator down while doing the testing and comparing.
Thanks, but I'm not sure I understand. Are you recommending I remove the good board and re-install the defective one in the fridge, if so what tests should I perform? I don't know what an octopus tracer is!
 
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