PCB Diagnose - Washing Machine

[thyaguster]

Hello, first time posting here. I do occasional fixes, mostly component swapping - I don't have a deep knowledge on electronics. Hope I can get some help.

I've  got this washing machine Fagor FE-8010 pcb that stopped working . (Firstly it stopped responding to switches and/or not starting any program, then it died completely).
I found "W ASTRA P3 E" and "DPC-E8 94v-0" printed on the pcb, but can't find anything online related to it, neither any replacement pcb.

Photos here: https://mega.nz/#F!cBUSQaLA!2bgk2_CZktFmOB6CbDKC2Q

I can see 2 triacs(?) burned that I suppose are ft0103mn162, like the others.
There's black smoke near the choke and the adjacent IC chip (even more so on the back of pcb).
R4 and R121 were also black from smoke but I suspect it came from below. Though R4 is dead.

Would like to get some insight on what components to check and replace.
Thank you.

[nsrmagazin]

This PCB is a non-certain project. Replacing the black smoke and burned ICs is where to start from, but do keep in mind that something was not all right before the whole PCB died and that is your key problem. Probably a short or another burned component that was not noticed.

I found this:
https://www.ebay.com/itm/IR-BOARD-DPC-B1-94V-0-PCB-KB-V6-IFC130A-pXZ16016-A-IM32141-E0003194A-/112564678462
http://www.elektro-nahradnidily.cz/modul-na-desku-fagor-c42p017a8-p39286
https://www.made-in-china.com/products-search/hot-china-products/94v0_Circuit_Board_Factory.html

This is like a specification, i cant guarantee it fits your washing machine.
https://www.wellpcb.com/special/what-you-need-know-about-94v-0-circuit.html

[fzabkar]

I suspect that R4 is the "startup" resistor for the 8-pin IC. This area is the AC-DC power supply. IME black dust is quite common in this area and is not necessarily indicative of component failure. I would clean it up with a toothbrush and isopropyl alcohol. Can you tell us the markings on the IC? It appears to be a Fairchild part.

There appear to be two DC supplies on the secondary side of the transformer, 12V for the relays and 5V for the microcontroller. Be aware that the entire PCB is at mains potential, so be very careful.

[thyaguster]

Yeah I was looking into testing that fairchild q321, because it also looks a little black around, even though it's really close to the choke.

[fzabkar]

I suspect that "q321" may be a YWW (Year / Week) date code. The top line is probably the part ID.

I would obtain a datasheet for this IC and examine its application circuit. I wouldn't be ready to condemn the IC just yet. O/C startup resistors are common failures in these types of circuits. That may be all that is necessary to restore the DC supplies.

[thyaguster]

It says "F BBHAC Q321", but I didn't find anything googling BBHAC.

I did find when searching for Q321
https://www.kynix.com/Detail/587684/Q321.html

This is FSQ321, seems to be the same, but can't be sure.
https://www.datasheets360.com/part/detail/fsq321/2739237769812975745/

About the possible cause of the failure you talk about the resistors, would those resistors burn the triacs?

[fzabkar]

Sorry, you're right. That does appear to be the correct IC. The startup resistor would be connected to pin #5 (Vstr). The application circuit has a 100k resistor in this position, albeit for a different chip.

I believe the two faults (resistor and triacs) are unrelated. Triacs would be associated with motors and solenoids, so that's where I'd be looking, especially if a triac fails again after replacement.

[thyaguster]

Yes, you're correct, R4 goes to IC pin #5.
Thanks for clarifying that about the triacs, I already suspected that because I could see that they're connected either to a relay and/or the pcb fingers where the rest of the machine connects. And I also knew that the machine wouldn't start any program first (fits with triac/relay failure I guess), it was only after some retries to start it and leaving it on for some hours that the pcb died completely. Also I have fixed a few machine boards by replacing resistors and stuff like that, but on this one I was afraid to just do that because I saw damage on different pcb parts.
I guess I'll start by replacing R4 and test the board without connecting any peripheral hardware.
I don't think I'll find those triacs on stock on any shop on my city, would it be any problem in removing them from the pcb and just test the board for the DC part?

Thanks for the help, you've been very helpful.

[fzabkar]

I think it should be OK to test the PCB without the triacs. Another common failure in PSUs of this type is the electrolytic capacitor that filters the voltage on Vcc. It tends to dry out and develop high ESR. You might like to replace it with a low ESR type.

BTW, I often see "dust" in high voltage areas, particularly around the focus resistors in CRT TVs (although these voltages are much higher than yours).

WARNING: If the supply doesn't start, there will be 350VDC on the main filter capacitor. You may need to discharge this with a suitable load. To this end I momentarily connect a 100W incandescent lamp across the capacitor terminals.

[thyaguster]

So I changed that resistor and the capacitors and it's working again. I didn't change the triacs yet, because I can't easily find them.
Would a z0301mn replace it? I tried some tools online that compare for replacements, but I have to admit, there are too many values for me to make a decision.
Or should I just get the Fagor part anyway, even if it takes longer and it's more expensive?

Also I may have found the fault that started this, I found some wires that were rubbing against something that exposed the copper. There were like 5 wires like this. No peripheral component seems shorted though.

[fzabkar]

The Triac part number is FT0103MN. "162" is a date code.

Fagor part markings:
https://www.fagorelectronica.com/images/download/semiconductor/Fagor-marking.pdf (page 6)

FT0103MN, Fagor, logic level Triac, 1A, 600V, Igt = 3mA, Vgt = 1.3V
https://www.fagorelectronica.com/images/download/semiconductor/ft01nll.pdf

The Z0103MN looks like a good match:
https://media.digikey.com/pdf/Data%20Sheets/ON%20Semiconductor%20PDFs/Z0103_107_109MN.pdf

[thyaguster]

So, I didn't update the thread, because I was waiting for the parts and got a spare machine. So even though I had already replace the parts on the PCB I only tested it now.
Thank you all for all the help, everything seems to be working fine and as intended