Washing machine PCB - component replacement  - Page 1
Forum section: electronics / repair

author: thyaguster
author_rank: Newbie
timestamp: April 17, 2021, 11:21:16 pm
content: So I had a problem on this board before, but with the help of fellow users got it working, it has been washing fine since then!But this week a slug crawled on the PCB (yeah...) and both got toasted. I can see that R120 is dead but that's the easy part.The slug was lodged near D15-D7, touching the transformer. I suspect the transformer died since it burned a hole on the PCB itself (only on one leg). I wanted to remove it to test and clean the PCB around that area but the transformer started to disintegrate as it was very brittle.Now the thing is I don't know much about electronics, and when I search for the numbers on top of it I can't find anything. Can someone help me find a replacement?Also, what should or could I also test along that area/circuitry?Photos here:https://mega.nz/#F!cBUSQaLA!2bgk2_CZktFmOB6CbDKC2Q(these photos were taken before the first fix, so they have burnt components (triacs) that have been replaced)

author: james_s
author_rank: Super Contributor
timestamp: April 18, 2021, 03:15:26 am
content: What's that 8 pin IC next to the transformer? The transformer is probably a custom part, you won't be able to buy a replacement off the shelf. You may be able to repair it though, if you can find a datasheet for that IC which I suspect is the power supply controller it will probably have an example circuit similar to what is used there. It's also possible you could just add a separate external DC supply and disable the damaged one.

author: thyaguster
author_rank: Newbie
timestamp: April 18, 2021, 08:35:46 pm
content: Quote from: thyaguster on January 25, 2019, 02:55:21 amQuoted myself from the old thread, since it was already identified.

author: perieanuo
author_rank: Frequent Contributor
timestamp: April 19, 2021, 09:28:54 am
content: Quote from: thyaguster on April 17, 2021, 11:21:16 pmhi,first, i really don't see hole in smps transformer area, maybe you're mistaking the cuts that separate hot and cold areasif the tnansformer is dead, you will never find him, if you are brave open it, undo the coils, note all like diameter and no of turns etcaetere, i mean make an identical transformer, but that's for the experienced people. maybe it's realistic to change the board or if you vahe space, put another supply with same voltage output levels ( maybe 2 voltages are made, but you can tell from filtering caps on smps transformer output).I doubt he was gone, i'd guess control circuit or surrounding components are dead, but if his 'disintegrate ', no way of repair him, maybe find some other tranformer body same size and 'clone' the disintegrated onebut after remaking the transformer you still have to deal with control IC and around him

author: fzabkar
author_rank: Super Contributor
timestamp: April 19, 2021, 06:47:29 pm
content: It appears that FSQ321 is the correct part, although Google Images shows different variations of part markings, some with "Q321" on the top line, others on the bottom line.Here is one that matches yours:https://tecsho.com/Detail/ای-سی-ها-(IC)/168026/FSQ-321-DIP-8https://www.mouser.com/ds/2/149/FSQ321-195587.pdf

author: Alti
author_rank: Frequent Contributor
timestamp: April 19, 2021, 07:15:58 pm
content: Check for opto-couplers on a PCB. If there aren't any then the only sensible way to turn on a triac in mains application is in QII and QIII by applying negative voltage. If that is the case then this burnt thing is a negative voltage offline switcher, non-isolated. So do not bother replacing it but simply add an AC/DCwallmartwall-wart(considering relay, looks like this is 9VDC powered).

author: james_s
author_rank: Super Contributor
timestamp: April 19, 2021, 11:25:28 pm
content: Walmart? Did you mean wall wart? I would use one of the small potted power supply modules personally, not a wall wart. You'll want to make sure you remove enough parts of the original PSU to isolate it.