Identifying burned component on refrigerator controller - Page 1
Forum section: electronics / beginners

author: sanchaz12
author_rank: Regular Contributor
timestamp: January 11, 2024, 05:29:46 pm
content: Hi,Today I came home to my refrigerator/freezer combo beeping that the freezer temperature was too high.I did not hear the compressor running, and checking the wires to it there was no voltage present when it should be running.I found the controller board at the back where the 230V AC connects to, as well as the compressor and some other things,I opened it up and found a burned out component next to the main 220 uF 400V filter cap. It connects to the bottom of the PCB to the negative side of the filter cap, and the other side seems to connect to a ground plane on the side where the 5N50F (500V 5A N-Channel) MOSFETs are connected to with their source pin. In the state it is in now it measures 1.53 k\$\Omega\$.Since the freezer is slowly defrosting at the moment I am curious if this is the reason the compressor isn't working, and what this component even is and if I could just bridge it for the time being.Any help would be appreciated!

author: JJ_023
author_rank: Frequent Contributor
timestamp: January 11, 2024, 06:26:46 pm
content: I would not try bridging it because you don't know if there are other faults on the board which could lead to a cascading effect of faults. Have you played with the board to see what is short and what is open?

author: magic
author_rank: Super Contributor
timestamp: January 11, 2024, 06:42:56 pm
content: This looks like a low value resistor used for current monitoring. It blew because its permissible current has been exceeded, most likely for unrelated reasons. The same may easily happen to a replacement, unless the root cause of overcurrent is found and resolved. Depending on its role, replacing with wrong value may easily make things worse (and is rather unlikely to make them better).

author: MarkT
author_rank: Frequent Contributor
timestamp: January 11, 2024, 06:47:58 pm
content: I would guess some MOSFETs blew up, or went into cross-conduction (aka shoot-through) and burnt it out - that failure could have cascaded to many other components too like gate-driver chips and the MCU even....If you are lucky the motor siezed and the extra current cooked the resistor and the other components are OK, but who knows?

author: sanchaz12
author_rank: Regular Contributor
timestamp: January 11, 2024, 06:50:28 pm
content: Thanks, in the chaos of what to do with the contents of my freezer I only thought of replacing this one component. I just measured the mosfets and 5 of 6 measure fine on diode check between source-drain (~490mV one way, open the other way), except one that measures 47mV both ways. I guess when it shorted it blew this component up (fusible resistor perhaps?).I'll look further into it if I can find more things that don't measure right. I suspect replacing this one shorted mosfet and the other component will be enough, but I haven't tested the compressor itself for resistance as I need to look into it what the wiring is since it has three wires connecting to the board.Also, is a mosfet likely to short in case the compressor may have locked up?

author: magic
author_rank: Super Contributor
timestamp: January 11, 2024, 07:01:26 pm
content: I think it's not a fuse but a current sense resistor, there are two vias under it which appear to connect with internal layer tracks going to somewhere.BTW, if you are unlucky, the "somewhere" may have blown too when the resistor went open circuit, if it wasn't sufficiently protected.

author: sanchaz12
author_rank: Regular Contributor
timestamp: January 12, 2024, 02:58:28 pm
content: Thanks for the input.Meanwhile I found another mosfet to be shorted (source to gate), and the switching diode and 22R0 resistor connecting to that gate have gone open circuit.Besides that the 5A 250V slow-blow fuse at the mains input side also tripped.Luckily I found an image of an intact board, and the burned component was originally a SMD resistor with value 'R075'. As you pointed out, probably acting as a current sense resistor.I have ordered replacement mosfets, BAS16 switching diodes, both the R705 and 22R0 resistors and a pack of identical spec fuses.If it fixes it that would be great, if not it's no big deal. I found a complete replacement board for about 1/3 the price of a new fridge/freezer combo, but that's not worth it for me at least.

author: magic
author_rank: Super Contributor
timestamp: January 12, 2024, 03:29:40 pm
content: Quote from: sanchaz12 on January 12, 2024, 02:58:28 pmThe current which blew these components went somewhere. Chances are that this IR gate driver chip is blown as well. Check if the pin which drove the failed MOSFET isn't shorted to one or both rails, or open (compare with other pins). Check if the whole chip isn't a dead short between VCC and GND.And as MarkT said, the next link in the chain is likely some MCU. If this blows, and you don't have the firmware, it's game over for this board.Quote from: sanchaz12 on January 12, 2024, 02:58:28 pmNot a good sign IMO...

author: sanchaz12
author_rank: Regular Contributor
timestamp: January 12, 2024, 04:06:35 pm
content: Quote from: magic on January 12, 2024, 03:29:40 pmAfter I found the 5A 250V fuse to have blown and reading your comment I think the chances that it will take more than 'just a few parts' are becoming low. Something in there took more than 1150W causing the fuse to blow.The control panel at the front where the main power switch is located is still powering on and working, and I found the mains is connected to the compressor board, where the live and neutral branch off to an adjacent three-wire connector which connects to the control panel, and the third wire is most likely the switched live return from the control board to supply the compressor board as this third wire is the only path feeding into the 5A fuse on the compressor board.I just received an e-mail from RS-Online where I ordered the parts that the order is cancelled as I am not a business customer, perhaps a good thing since I did not check the gate driver or MCU yet.Perhaps a good thing to do next is checking if the compressor is still working, and then decide whether to spend more time diagnosing this board or sourcing a (used) replacement module.

author: Stray Electron
author_rank: Super Contributor
timestamp: January 12, 2024, 09:27:23 pm
content: I can't help you with identifying the part but I will tell you that I was given a very expensive top end refrigerator that had some problems. I took the part numbers from the circuit boards and bought some used boards from E-bay (guaranteed of course) and the 2nd board fixed the problem. The first board cost me about $40 and it didn't fix the problem. The second board cost about $80 and it did fix the problem. The point is it will probably be quicker and possibly cheaper to just replace the circuit board. My refrigerator circuit boards didn't have any obvious damage but there were only three circuit boards in it so I just started swapping boards.