Need help to repair my washing machine

[marco-ITA]

Hello all,

I kindly ask for help to repair my washing machine. I've sone some simple repairment in the past, I tried to do my homeworks but I think this is far over my possibilities.
I self-taught some basic electronics just to use PIC/arduino, I have no big problems understanding digital electronics (i'm a programmer), but analog electronics it's like sorcery to me.   

The model is an italian brand ARDO (gone bust) TL127LW, it doesn't power on (dead) and I think (HOPE!) it's a power supply problem.
I haven't find schematics or useful information on internet.

This is the electronic board, I think it's a three-layer one (I cannot follow traces flipping the board):



on the opposite side there are only SMD leds, a 4 digit led display and an IC (CAP200DG) placed between the legs of the green 1uF capacitor C1.

I guess that the power supply section follow this scheme:
https://hackaday.com/2017/04/04/the-shocking-truth-about-transformerless-power-supplies/
and that CAP200DG it's there only for safety reason.

I've tested C1, C2, R1, R2, D1 and D2 and all are ok. They let test them on the board, but i desoldered C1 and R2 to be sure and there was OK.





I guess also the problem lies near here:



I think those are 12V zener, right? Voltage across Z1 is 9.8v and Z2 is 40v (!!), and it's the same on the near capacitors respectively, both marked 32v (!!)
I haven't found anything useful about IC2 (marked WT 72 s in no particular order) and I have no clues on what is it.

For what i've understood there is a stepped regulation in voltage and the last stage is feeded on VR1 (KY5033) to feed the microcontroller, but from here I'm lost.

Can you help me?

Thanks in advance and sorry for my english,

Marco

EDIT: some problem in pictures order

[Runco990]

Well, this is NOT the usual proper troubleshooting way... but....

I had the same problem with my Whirlpool washing machine.  I found absolutely nothing wrong with the control board.  But since it had only a few capacitors on it, and I change a LOT of bad capacitors I just "shot gunned" it.  Works perfectly.

I then measured the old capacitors which "technically" were still "OK" in any device that is engineered with a tolerance.  This obviously was set up with NO tolerance whatsoever, so it would fail in a few years.  I did up the capacitor values a little to build in MORE tolerance.

Those caps look like the typical bargain basement types spec'd to the cheapest possible build.

I'd replace them ANYWAY.  If it still won't start, you have some proper troubleshooting to do, but generally the caps in those boards are absolute trash.  Can't hurt to try that first if you find nothing else wrong.

[FIXITNOW2003]

only Ardo info i could find if it helps

[marco-ITA]

Thanks, I'll check for similarities

[marco-ITA]

Well, this is NOT the usual proper troubleshooting way... but....

I had the same problem with my Whirlpool washing machine.  I found absolutely nothing wrong with the control board.  But since it had only a few capacitors on it, and I change a LOT of bad capacitors I just "shot gunned" it.  Works perfectly.

I then measured the old capacitors which "technically" were still "OK" in any device that is engineered with a tolerance.  This obviously was set up with NO tolerance whatsoever, so it would fail in a few years.  I did up the capacitor values a little to build in MORE tolerance.

Those caps look like the typical bargain basement types spec'd to the cheapest possible build.

I'd replace them ANYWAY.  If it still won't start, you have some proper troubleshooting to do, but generally the caps in those boards are absolute trash.  Can't hurt to try that first if you find nothing else wrong.

Well... why not!

Checked my capacitor reservoir, I miss only a value,

KA-KLACK!!



I'M COMING!

 

[MathWizard]

If it's still not working, and you have a DMM and some time, I'd make a map of where the power goes when it comes in. Some of it goes to relay's like for the motors, but somewhere very close by, there should be some little step down transformer, and some rectifier circuit.  Or there could be a little SMPS section, that will make the low voltages rails for all the control circuits and chips.

There's probable some 5 or 12V regulator, or some little circuit for the low voltage rails. And on some stuff anyways, nothing else can work, until those little rails are working.

[hesam.moshiri]

Hi,

You did not mention the problem itself, does the board not power ON?

is there any burning sign on the PCB?

How did you test the capacitors? DMM is not a good tool at all. In many cases, ESR is high, but the capacitance shows OK, even on the LCR. watch this:



Also, check the power rail of the Microcontroller (MLCC capacitors) for any short circuit to see if the MCU is fine

[marco-ITA]

Five capacitors and 2 zener later...


 

If it's still not working, and you have a DMM and some time, I'd make a map of where the power goes when it comes in. Some of it goes to relay's like for the motors, but somewhere very close by, there should be some little step down transformer, and some rectifier circuit.  Or there could be a little SMPS section, that will make the low voltages rails for all the control circuits and chips.

There's probable some 5 or 12V regulator, or some little circuit for the low voltage rails. And on some stuff anyways, nothing else can work, until those little rails are working.

Yes, you are right. The problem was in the 12v zener that i marked Z2 in my photo, and also C-Z2, C-Z1 and the big capacitor down in the photo failed (well, probably C-Z1 was destroyed by me trying to desolder... )

Hi,

You did not mention the problem itself, does the board not power ON?

is there any burning sign on the PCB?

How did you test the capacitors? DMM is not a good tool at all. In many cases, ESR is high, but the capacitance shows OK, even on the LCR. watch this:

Also, check the power rail of the Microcontroller (MLCC capacitors) for any short circuit to see if the MCU is fine

Thanks for the instructive video 

I borrow a capacimeter from my friend, I've checked all my spares before changing, in two cases the originals were better than the spares, so I put them back.
Yes, I did not mention that the circuit was close (no fuses/safety triggered) and no obvious signs of failure were evident.

The repair is a bin Frankenstein-ish  one capacitor is quite bigger than the original so I had to cut the plastic cover around it, and the zener was not smd (so I lost one zener trying to fit it in place) so it's a bit "acrobatic on the circuit" now, but, anyway...



Hope it last!

Thanks for all your help and support! 

[CaptDon]

Very nice to hear you got it working! If it was a General Electric and you were here in the states I would have said "take it to the Higginns Appliance Shoot in Pennsylvania and enjoy blasting holes in it and then loading it with some C4 for the 'final repair'". Want some interesting reading, check out the one-star reviews online for GE appliances.

[marco-ITA]

Very nice to hear you got it working! If it was a General Electric and you were here in the states I would have said "take it to the Higginns Appliance Shoot in Pennsylvania and enjoy blasting holes in it and then loading it with some C4 for the 'final repair'".

LOL  it gives the idea.

Im my case I don't know if the board was planned correctly to not fail catastrophically, or I am just lucky enough. ARDO is a not-well-known (so... now is dead) brand, build by Merloni group, a big builder/reseller with many brands some years ago. It had a good build quality, but the world is going all the same direction: fewer builders, many brands differing mostly in aesthetic/accessories but with the same core components, cheap quality to have aggressive prices.