LG Washer/Dryer Power Fail

[petehall347]

Re: LG Washer/Dryer Power Fail

i thought d243 is marked as a zener on the diagram then i made it bigger and now its a schottky .

[CapLeaker]

Re: LG Washer/Dryer Power Fail

would have been nice to see if a new TOP246 would have done the same, but at least it is working now with the new TOP248.

[petehall347]

Re: LG Washer/Dryer Power Fail

if its running cooler it is better . surely the rating is maximum and not normal running . higher rating fuses might well work for a while . a new motor would clinch the deal

[AdrianM]

Re: LG Washer/Dryer Power Fail

would have been nice to see if a new TOP246 would have done the same, but at least it is working now with the new TOP248.

These parts seem to have rather high on-resistances in general so it feels right to take this opportunity to waste a little less power.

But yes, I must admit to being curious myself about a like-for-like replacement however the repeated tear-downs and re-building were beginning to wear both me and the board connectors down. I strongly suspect a direct swap would yield the same result but I did actually buy a new TOP246 as well as the TOP248. When I get a chance I therefore plan to breadboard a small test circuit following the procedure outlined in the datasheet and compare their on-resistances.

[momaka]

Re: LG Washer/Dryer Power Fail

Good to hear it's fixed and all running good now! Let's hope it stays that way too. The dryer fan will have to try much harder now to kill the PSU. But if it uses crappy bearings, maybe not. On that note, it probably uses sleeve bearings, so should have dropped a bit of oil on them (if that's even possible, as some fans are pretty good at making their bearings inaccessible.) But hey, if the washer makes it another 3 or more years, I'd say you still did a good job. At least that's how much I am expecting to get out of my tub bearing job. Some of the reviews of the really cheap bearings online say they only got a year, which is pretty terrible of course. I think 3 years is just about enough to say the repair was worthwhile (and of course, if more, then that's all fine).
Yeah, doing a bearing job is pretty much a full disassembly process. But I didn't have to touch any electronics, though. Just some blood, sweat, and tears to get those stupid bearings out.

[redwire]

Re: LG Washer/Dryer Power Fail

The best repair is when you fix it and up the power.

TOPSwitch gets hotter, on-resistance goes up, TOPSwitch gets hotter... and repeat. From 25°C to 100°C it goes up 150%
This is also why I am in favour of the larger part, less thermal runaway.

Does it seem strange to price-point these TOPSwitches at silly levels every few watts?
Is 0.5mm more silicon for the mosfet really going to cause price to skyrocket?

[CapLeaker]

Re: LG Washer/Dryer Power Fail

Don't get me wrong, I am also in favor of the larger TOP248 and I would have done the same, given that same situation.

I just wanted to figure out if a new TOP246 would have done the same, as I mentioned before in my post #4, since they do fail like this for some reason. Like redwire stated in his last post "thermal runaway".

[AdrianM]

Re: LG Washer/Dryer Power Fail

Topic Update: Well, after 2+ years of continued use, the machine died in the middle of a drying cycle on Monday. My immediate thought was that at least I had bought a decent amount of extra time - it's now 8 years old and it wouldn't be so bad if it was finally time to buy a new one. But...

Curiosity got me to have a look to see what failed this time. The fact that it went completely dead (no panel lights or response whatsoever) hinted at PSU again. Fuses all OK? Check. 240V on PSU input? Check. 12V/22V on the output? Nope.

A quick diode test revealed that D243 had failed short-circuit. This was the diode I that I replaced with a 2A 100V PIV Schottky that I had to hand at the time. I couldn't identify the original but I thought this ought to be OK. Obviously not. Anyway, I grabbed a 3A 200V Schottky and replaced the 1000u cap that follows it (after having been subjected to AC I thought this might be a good idea) and to my delight it all sprang back into life. Very happy with that. I've updated this topic in case anyone attempting a similar repair finds it helpful. D243 is now a Diodes Inc SMC case designated: ES3D-13-F (It just about squeezes into the gap between the diodes on either side.)

[redwire]

Re: LG Washer/Dryer Power Fail

Thanks for the update.
The diode D243 is for 22V fan motor it seems. An ES3 is a normal diode 0.9Vf and will run ~20% hotter than Schottky SS36 0.75Vf for example but hopefully the upsizing is tough enough.
Hard to know how much current the fan motor uses, and it might go up with age.

Which TOPSwitch did you go with, the original TOP246YN?

[AdrianM]

Re: LG Washer/Dryer Power Fail

Oh yes redwire, you're right - I misidentified the ES3 part as a Shottky when it is in fact a fast Silicon switching diode as you say. The App note in the datasheet for a Multiple Output, 60 W, 185-265 VAC Input Power Supply uses fast Silicon diodes in all the higher voltage outputs so I figured it would be OK.


Unfortunately the LG PSU circuit only gets feedback from the 16.5V rail so the loading from the dryer fan motor leaves it with a poorly regulated voltage. With no load it puts out 23.5V dropping to 19.5V when the fan is running. The max current I measured was around 0.75A so the diode is dissipating around 0.675W so a Shottky would have been better. Oh well, next time maybe.

Indeed I replaced the TOP246Y with a TOP248Y which runs so much cooler!

[redwire]

Re: LG Washer/Dryer Power Fail

OK good just for anyone else who needs to fix an LG combo washer dryer model 1480YDS.
You were really thorough with the repair and have some good data.
So expensive to just toss them out and replace them over a few underrated semi's that are the problem.

[hugokernel]

Re: LG Washer/Dryer Power Fail

Hi,

I'm currently trying to repair a LG Washer F12952WH (sell on the french market 10 years ago), power board is EBR65873657 / EAX61526804.

The symptoms are simple: nothing happens when the button is pressed, after disassembling the power board (ref EBR65873657), I noticed that the fuse (220V, 8A) had blown and the power resistor (10 Ohms, 5W) used in series with the ignition button is dead.

I changed the 2 but when I press the ignition button, the resistor burns out immediately.

After going through this whole thread and looking at a lot of repairs, reading a lot of comments (https://www.youtube.com/watch?app=desktop&v=uCxA34JIJWQ, https://www.youtube.com/watch? v=CBWepvnvET8), I have unsoldered the TOP246 in order to test it, I have the feeling that it is not out of order (no short-circuit on its pins), moreover, I have put back a power resistor with a higher value (47k Ohms) and I have connected only the 2 connectors (the 2 colored ones), when I press the ignition button, the resistor heats up strongly (even though the TOP246 is not present).

My guess is that because the TOP246 isn't present, and therefore there's no power supply to the control electronics, the ignition relay doesn't switch on, and so the current the washing machine needs passes through the power resistor, causing it to heat up and destroy itself.

I have 2 theories:
- The TOP246 is out of order
- One of the main relay is out of order

Do you have any advice on this?
Thank you in advance.

[stj]

Re: LG Washer/Dryer Power Fail

check the relays for burned contacts or open coils

[hugokernel]

Re: LG Washer/Dryer Power Fail

check the relays for burned contacts or open coils

The relay coil seems to be good (150 ohms measured, same value for the other 2 relays)

[CapLeaker]

Re: LG Washer/Dryer Power Fail

post some straight shot, high resolution pictures. So we can see something. for a 5w resistor to fail, there has to be a dead short somewhere.

[lotas]

Re: LG Washer/Dryer Power Fail

The short is most likely in the module (motor driver) under the radiator, check the resistance on the power capacitor.

[hugokernel]

Re: LG Washer/Dryer Power Fail

The short is most likely in the module (motor driver) under the radiator, check the resistance on the power capacitor.

Hi,

Thank you for your answers.

I just checked the motor driver and apparently, the problem come from it.

All the points in red are shorted and connected to ground, so it looks like the driver is dead.

Does anyone know the reference number of this driver (I didn't see any reference, wasn't sure I'd be able to desolder it, and wanted to make sure I could get one before venturing any further.)?

[lotas]

Re: LG Washer/Dryer Power Fail

Carefully bite off the legs on one side with thin nippers and tilt them onto the top of the driver and there will be a marking on the other side.

[lotas]

Re: LG Washer/Dryer Power Fail

Then you can also take a bite, just do not bend the module itself too much here and there, so as not to damage the heels where it is sealed, then each remaining pin will be easy to unsolder and install a new module.

[hugokernel]

Re: LG Washer/Dryer Power Fail

Then you can also take a bite, just do not bend the module itself too much here and there, so as not to damage the heels where it is sealed, then each remaining pin will be easy to unsolder and install a new module.

Removing component success, thx.

The reference of the motor driver is PS21964-4S Mutsibishi Electric (datasheet: Datasheet)

There is electrical continuity between all the points in red.



Correct me if I'm wrong but I think there's a nice internal short circuit?