KitchenAid/Whirlpool PCB issues

[keithwbloom]

I have a drawer type under-counter refrigerator that has a wonky PCB. I would normally by now have just given up and ordered a new replacement, but apparently the manufacturer/supplier for this particular board was wiped out in the mainland Japan tsunami a few years ago. So the only option is to repair. There is a service that does repair/recondition for a fee, and I have already used them without success. Not even at all sure they did anything to my board at all, as all components look undisturbed.

Here's the wonky part — it works fine when it is not installed in the unit vertically. While it is laying in the floor behind the unit, the fridge works perfectly, albeit the power supply relay is more audible (louder click.) Once it is installed vertically in the slot that holds the housing, it starts cycling power every 2-3 minutes, and eventually starts timing out completely for 10 minutes or so at a time and then repeats the loop.

So amateur that I am, and after having great success with replacing bad caps and MOSFETs on a couple of power supplies using the DIYs on this forum, I am back again because I am solidly at my wit's end.

So here's the PCB:


Another view, closeup of some of the caps:


And this is how it sits horizontally on the floor and works:


There is a thermal fuse that attaches to the outside of the metal housing, which I thought may be suspect, but even when left unattached and dangling away from housing when the board assembly is reinstalled, the cycle/timeout symptoms still occur


So my question... are there any component types on that PCB that might suddenly become hyper sensitive to orientation after years of normal operations?

I should add that I have examined as closely as I could with magnification the connectors and harness wires for stress breaks or any other kind of problem that might occur when they are manipulated into position for board installation. I did not see anything that looked amiss.

[budm]

Re: KitchenAid/Whirlpool PCB issues

What happen when you have it laying on the floor and you poke it with plastic or wooden stick? Since it is mounted in the metal box, you do not see it making fault contact with the metal box and what happen if you move the box in different orientation?

[vinceroger69]

Re: KitchenAid/Whirlpool PCB issues

Try resoldering the large transformer thats on the board ive seen them become dry jointed on various boards.

[pfofit]

Re: KitchenAid/Whirlpool PCB issues

Model # please and does it have auto defrost.?
Need an in focus pic of the underside. The relays as well have their solder connections go bad, so resolder that T9 relay

Moving the board correcting the issue probably indicates a bad joint, cracked foil or flaky connector harness. Look inside the harness ends to see if female pins are spread to far apart.

That thermal fuse is most likely a thermostat or re settable over temp cutoff. Where exactly is it located? Pic!

[keithwbloom]

Re: KitchenAid/Whirlpool PCB issues

Thanks for everyone's feedback. I'll post additional photos and feedback shortly. I have a macro lens for my iPhone I will use for extreme closeups.

[keithwbloom]

Re: KitchenAid/Whirlpool PCB issues

PCB full view overhead and then four quarters
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PCB reverse side full view overhead and then four quarters
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The service sticker from the authorized agent
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The trans
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The relay
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Closeup of caps farm
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The four MOSFETs (I think that's what they are called)
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Some other disc style caps:
Photo 23:


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Three photos of where PCB assembly is located when installed
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Where the thermal fuse is mounted on outside of PCB case when installed
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When mounted, PCB is isolated on plastic clips, no ground contact is made.
Photo 29:


Presently testing in this vertical orientation outside of frame mount
Photo 30:

[stj]

Re: KitchenAid/Whirlpool PCB issues

it's bad solder joints, i can see it in the foto's

first resolder all the connectors and anything large.
by resolder i mean remove the old solder first, not splash more ontop.

the cables pull and put alot of stress on the connectors.

next look at any soldering left for rings or halo's / shadows and resolder them too.

[pfofit]

Re: KitchenAid/Whirlpool PCB issues

Start with these joints and any others that look the same.
as per other techniques on soldering, remember you have a dual sided board so you need to get solder to other side for good connections.

But too much heat for too long and you may start to lift foils
cheers, good luck.

[keithwbloom]

Re: KitchenAid/Whirlpool PCB issues

Start with these joints and any others that look the same.
as per other techniques on soldering, remember you have a dual sided board so you need to get solder to other side for good connections.

But too much heat for too long and you may start to lift foils
cheers, good luck.

So I have a hot air rework station and a squeeze bulb vac. I think I can clean these joins and resolder, probably will do most if not all of the connectors and large components.

If you don't mind briefly explaining, what is wrong with these joins and what may have cause them to deteriorate over time? Should I take any further precautions if the fix is successful?

Cheers,

Keith

[stj]

Re: KitchenAid/Whirlpool PCB issues

vibration and gravity make large parts pull on the joints.
this makes the solder crack into 2 parts - the part on the wire and the part on the pad.

the cracks are very fine, but once you know what your looking for - they are easy to spot.

they look like a ring or halo around half way between the center and outside of the joint.

[pfofit]

Re: KitchenAid/Whirlpool PCB issues

Hi keith.
They joints can be bad for a few reasons.
They are large heavy components with heavy wires that didn't get heated enough during the solder wave process. In essence their large size and/or what the leads are connected to act like a large heat sink and therefore the joint is "cold". Cold solder joint.

This results in a crappy joint that is brittle and not really stuck to the two pieces that one is trying to join. The joints should be shiny and even.
They can be seen by your photos. They tend to be discoloured,pitted. In your photos i can see a burnt,pitted discoloured joint like where the pin is in the middle of the solder. This shows that the joint is a poor connection and the joint is therefore heating up. Which causes more deterioration of the joint and so on. Now, we know you have an intermittent issue and your joints may be so-so for now but they won't last because they don't look good so one would start with the easy stuff.

As well, after these large components are installed the weight and vibration of the component can stress even good joints. Also, removing and replacing plug connectors can weaken the joint.

Below are a few images of the many bad appliances board in my spare parts bin.
To the unknowing eye, in the first image, it doesn't appear so obvious, but zooming in with the second pic shows the end joints are starting to crack. Both of these bad joints are on the ends of a plug connector. The left one indicated is not cracked all the way around yet but the other is. So any flex/ movement of the harness combined with changing environmental temperatures would cause the joints to mess around th electronics.

3 & 4 are what happens when it's not corrected in time. This is a stove board where the two halfs fold together and are about a half inch apart when assembled. The right side is AC ac power and the other is low voltage Mirco and stuff.
When the bad joints on the relay connection for the the bake element further degraded due to heat etc, 10-15 amps at 220 started sputtering across the corroded connection and then started arcing all over the place, got to the other side and we all know that micros don't like 220 AC. The white trace lines on the left are the foil vaporized off the board

The 5th pic is just another I threw in that was even more violent and actually burned down into the physical board once the arc welding got going.

These stove boards are a bad design when the joints go bad. The back sides of the boards have conformal coating so sometimes the joint pops and blows carbon all over and is easy washed off with no harm. A new relay and rebuild the foil respray a coating and good to go. However, i got a bin of dozens where the damage is catastrophic. Since they started years ago, removing the bank of screw in fuses there is nothing to shut it down except the main panel 40 amp breaker or the board foil. Of coarse we all know which is gonna lose.

cheers