Electrolux EWT904 (Simpson brand) - Top Loader Washing Machine

[Wodger]

Hi Everyone,

I'm looking for a circuit diagram layout for the power board on this machine, so I can attempt to troubleshoot, As per the sicker on the back:

SIMPSON/Electrolux
W2104A-V06

I've repaired and replaced this board once but now I have 2 dead powerboards. Usually the capacitors blow on this design, but recently I found no problems with the capacitors and finally found the offline switcher (LNK306PN) had burned. On replacement, one board worked for a while but now is dead again (no beep when powered up from wall supply), and the other older board didn't work even when the offline switcher that looked damaged was replaced.

Thanks for your time.

Pete

[CapLeaker]

Post some high resolution, straight shot pictures front and back of the board. Let's see what we are dealing with here.

[Wodger]

Post some high resolution, straight shot pictures front and back of the board. Let's see what we are dealing with here.

Good day,

Thanks for responding. Attached are pictures of the board. I'm without power at the moment for another 6 hours and lighting and board design doesn't lend well to pictures (circuitboard is encased in a clear rubberized silicone material which makes repair of this board a headache). I have done top and bottom and then front and both sides.
From my investigation, the ptc resistor on the ac incoming line gets really hot to touch within 20 seconds of power applied.
The machine was functioning normally during a cycle then after draining was about to spin when the supply went dead. Found the 2nd inline 4.7uf cap furthest from ac-in bulged, but replaced both - no change.

Thanks,

Pete

[CapLeaker]

revisit the switcher bottom make sure it isn't dead and clean in between the pins. Joining the top 2 pins on each side is ok. Caps can look brand new, but yet be bad. Maybe wanna check all of them. If you get power from the switcher, but nothing on the motor drive, check out the SCR's, check the blue caps and make sure the resistors are within tolerance. There is another device between the SCRs and the little cap. What is that?

[Wodger]

revisit the switcher bottom make sure it isn't dead and clean in between the pins. Joining the top 2 pins on each side is ok. Caps can look brand new, but yet be bad. Maybe wanna check all of them. If you get power from the switcher, but nothing on the motor drive, check out the SCR's, check the blue caps and make sure the resistors are within tolerance. There is another device between the SCRs and the little cap. What is that?

Cheers for the advice - I will get back on this probably tomorrow night if I get energy (troubleshooting a Kia that is now refusing to start). Regarding your question what device is there, I assume your looking at the arrowed area on attached pic? - Diodes - I will of course make sure they are working properly.

I will advise of my findings.

Pete

[CapLeaker]

I did some mark ups for you. I can clearly see one SCR on a heat sink. Also something needs to drive the gate of the SCR. Caps near a heat sink are always suspect too. Check the diodes, the resistor. To get the best reading take it out of circuit or lift one leg.

[Wodger]

Hi mate,

Thanks for that😊I was just about to head out to do the jobs for the day. Attached is a closeup picture looking from the right side of your markup picture showing the part number of the question marked part. Hopefully, I have energy later to look at this as the laundry is building up.😂

Pete

[CapLeaker]

Hi mate,

Thanks for that😊I was just about to head out to do the jobs for the day. Attached is a closeup picture looking from the right side of your markup picture showing the part number of the question marked part. Hopefully, I have energy later to look at this as the laundry is building up.😂

Pete

That 7905 is a negative 5v regulator (-5V) also worth checking out.

[Wodger]

That 7905 is a negative 5v regulator (-5V) also worth checking out.

So I unsoldered the parts you circled plus the switcher (it made it so much easier to remove the silicone gunk from the board). And cleaned the board up as best as I could.
I tested the small smd resistors and capacitors on the back to the ac line 2 for continuity on either side and all but a couple sounded on connected side only (the remaining ones didn't sound at all) - I also tested the chunky smd diode and that appears working normally (first time I have seen a 2nd band on a diode casing - I'm not deep electronics specialist - trained in marine engineering).

Short stop for refreshments then will check removed parts.

Pete

[Wodger]

So I unsoldered the parts you circled plus the switcher (it made it so much easier to remove the silicone gunk from the board). And cleaned the board up as best as I could.
I tested the small smd resistors and capacitors on the back to the ac line 2 for continuity on either side and all but a couple sounded on connected side only (the remaining ones didn't sound at all) - I also tested the chunky smd diode and that appears working normally (first time I have seen a 2nd band on a diode casing - I'm not deep electronics specialist - trained in marine engineering).

Short stop for refreshments then will check removed parts.

Pete

Hi everyone,

So after removing the remaining 0.1uf capacitor / varistor / PTC on the ac line, found the PTC actually has "leaked" so I'm pretty confident that's dead, the yellow 0.1uf capacitor also appears dead giving open circuit on terminals, also dead is 470uf and 100uf electrolytic capacitors which don't appear to charge and remain shorted (going by analog multimeter). The varistors are a puzzle, I should have some sort of reading, but I get nothing from any of them.

The rest of the parts appear fine (checked SCR's, the 5V regulator, diodes, the voltage switcher and resistor).

I'm waiting on an answer for replacement parts (varistor and PTC are proving to be hard to find where I am located)

Pete

[CapLeaker]

Hi everyone,

So after removing the remaining 0.1uf capacitor / varistor / PTC on the ac line, found the PTC actually has "leaked" so I'm pretty confident that's dead, the yellow 0.1uf capacitor also appears dead giving open circuit on terminals, also dead is 470uf and 100uf electrolytic capacitors which don't appear to charge and remain shorted (going by analog multimeter). The varistors are a puzzle, I should have some sort of reading, but I get nothing from any of them.

The rest of the parts appear fine (checked SCR's, the 5V regulator, diodes, the voltage switcher and resistor).

I'm waiting on an answer for replacement parts (varistor and PTC are proving to be hard to find where I am located)

Pete

Open circuit reading on the square 0.1uF cap is normal, Other than that, you are well on your way. Hopefully you didn't miss anything, so better double check.

[Wodger]

Open circuit reading on the square 0.1uF cap is normal, Other than that, you are well on your way. Hopefully you didn't miss anything, so better double check.

Thats good to know, one less purchase. the varistors though, from what I've seen online, I should have some sort of reading with a multimeter, but I have nothing, not even a short.

Regarding the board, everything on the hot side has been removed and checked save for the 2 inductors (I'll check on them first thing tomorrow).

Pete

[CapLeaker]

The Varistor or MOV shour read open. If it has a reading its degraded already. The MOV can only take a finite amount of hits, each time degrading it more.