Samsung WD80N645OOW died mid-cycle

[stj]

put a lamp in series with the pump and see if the fuse doesnt blow

[sam_sam_sam]

put a lamp in series with the pump and see if the fuse doesnt blow

I would add one thing to this is dose the pump runs or is the light very bright if this could be your problem with the motor

[mrsith]

Replaced the pump, the fuse again, but I have a suty no power now. Nothing clicks, no leds go up, absolutely nothing. Checked main fuse again, confirmed with dmm that there's continuity between the mains plug and the main board connectors. Can't see any shorts etc either.

[CapLeaker]

Wasn't there another white glass fuse somwhere on the boards?

[mrsith]

I will check it in the morning. I don't understand why would it blow, if the washing machine was powering up with faulty pump and only blew a fuse when intended to use it, why would another fuse, on a different board, blow with new pump installed? Machine newer powered up or clicked any relay even once after I put it back together. It was continuously clicking the relay before replacing the pump along with the fuse.

I need some sleep, cannot think even remotely clear anymore lol.

[CapLeaker]

It could be that finally one of my favourite power IC's blew too.

[mrsith]

Fuse on the other board is fine. Your favourite kind of ic seems good too. I'm running out of ideas.

Just ckecked main relay with service psu, works fine.

[CapLeaker]

Hmm. So you got power going to, but nothing coming out of the board and the machine is absolutely dead? Mabe the STBY power is fuxed. I mean of these power supplies gotta be on 24/7. Also check larger wattage power resistors (SMD) they can unsolder themselves one side from the board. Filter inductors in the primary is another hidden spot. Transformers where the wire broke off at the leg, A fusible resistor, PWM, or a short on the secondary. Oh! Maybe it's one of the safety crap sensors! Sorry… still early here a working on downing my coffee!

[mrsith]

I have noticed that without the CN7 plugged in (front panel + inverter communication pins) the led on the main board blinks repeatedly.

Checked DC voltages there, instead of 5v I have unstable reading (jumping from 0-2.5v-0-3.2v-0-4.2v-0 etc, doesn't reach 5v), on 12v pin I'm getting 10-11.5v, randomly fluctuating.

[CapLeaker]

Well, at least you found something is a miss. Something is telling the pwm to shut down. It's still alive, other than that you wouldn't get anything at all.

[mrsith]

I've seen another thread on this forum, where someone had faulty voltage regulator (KIAsomething I think). It worked fine only if heated up, wasn't completely dead, like a zombie ic lol. Maybe something similar happens here?

Otherwise, what might be telling it to shut down? I'd consider just buying a new board if I was sure it'll work well lol. Getting desperate with laundry 🙃

Edit: when I think about it, isn't that the standby voltage that's wrong here? I mean this is required to power the sub pcb, which includes power button to run main relay.

Edit2: this 7-legged wonder description: "Including an auto standby function in the controller, the product achieves the low standby power by the automatic switching between the PWM operation in normal operation and the burst-oscillation under light load conditions." It also features protections:

　Overcurrent Protection (OCP) : Pulse-by-Pulse
　Overload Protection (OLP) : auto-restart
　Overvoltage Protection (OVP) : auto-restart
　Thermal Shutdown Protection (TSD) : auto-restart

According to datasheet it oscillated at 62khz, so it's not what I'm reading. Auto-restarting or pulse-by-pulse protecting?

Even another edit: measured Vcc pin voltage, at the beginning it was jumping between 18.something volts and 0, quite rapidly, after a while It was just over 2 volts. The initial jumping might've been caused by me trying to pry the probes through the resin though.
According to datsheet, it requires 15.3v to start. I need to figure out if it fails because of something else or itself.

Edit spree (still better than multiposting): checked ac voltage on middle pins of bridge rectifier (the large one just behind the fuse that was blowing), getting very small voltage (8-20), with occasional split second very high spikes.

Is there something else other than the rectifier itself that could cause this?

[mrsith]

Cant edit for the fifth time lol. DC volts on bridge rectifier initially jumped above 20v, then strarted decreasing. Unplugged and plugged back in when dropped under 10v, it raised to just around 11.5v and started to drop after a few seconds.

[CapLeaker]

Keep on digging and restore VCC. Maybe a bad startup resistor gone high in value or some thing along these lines. Without proper VCC it's not going to work. So this is priority. What is the part number of the pwm?

[mrsith]

It's str-W6053s.

I'm still trying to figure out why this all might've happened. With drain/circulation pumps, does polarity matter? Wouldn't think so as it's AC, but I remember the pump had pins marked L/N, I didn't remember which was which so just put orange wire to L, blue to N, guided by common sense. The machine acts the same even without pumps disconnected though.

Also why am I not getting stable AC on the bridge rectifier? It's the 1st component after the fuse, and both ac and dc measures taken from it seem wrong. Dc volts looked kinda similar to what I could read on PWM Vcc pin.

[stj]

no stable ac on a primary rectifier - check for loose spade terminals on everything upstream - seen it a lot on older stuff but never anything this new.
but worth a look, also check the mains filter - i'm sure it has one.

[mrsith]

I've been checking voltage on mainboard connectors, used the CN1 live line for plus (it's the main ac input for the board) and RY7 negative for minus (seen it has continuity against N line of the mains plug), got stable 245v there. I think everything goes through filter before it reaches the boards?

Spade terminals (the ones I'm aware of and I can somehow access) look brand new.

[CapLeaker]

Make a picture and draw or circle on it.

[mrsith]

Think I've found the problem. The N line goes through one of the main relay pins - confirmed via continuity against plug's N pin, relay's leg and the bridge rectifier leg. When I measure A voltage with CN7 L pin L and the relay plug (there's enough space to shove a probe between the plug and the relay when it's connected), I have stable 245v, but when I take the measurement using the relay leg on the other side of the board - which has continuity against that plug - I have same jumping voltage as measured on rectifier itself.

Gonna try reflowing that relay, if nothing changes I'll take it out and open it to see what's happening inside.

[CapLeaker]

I just wanted to say that there is nothing much in between the rectifier and the power cord, but you are in the right track. The relay could have burnt contacts not letting enough juice go through.

[mrsith]

Well I've made a mistake, it's the other pin of that relay that's supplying the N ac line. And it's normally closed so that relay has to be switched on first. This means there's whole another route of power here.

Starting with DF06S rectifier, I'm getting dc output of circa 50 volts, raising steadily (~10v at a time) to circa 110v,then drops again to 50s and raises again. Is that normal?

Edit: also found a tiny T4 marked diode, just next to the relay (looks like it's connected to the relays coil), which is open, doesn't conduct anything any way.