Control Board Failure

[sburtchin]

Is anyone up for a real troubleshooting chalenge?

I didn't know where to put this, but I thought you TV geeks might want to test your skills. I suspect problems with a digital controller board of a major item in the home (not a TV or computer), but I am almost certain that the problem originated with one of the peripheral devices (which has been acting up for years). This board stores events and they all point to this same peripheral.

I have tried forums that specialize in this item, but they all want to take the easy way out and have me replace the whole item, or swap out one or more $200 components by trial and error.

On the Control Board, one resistor gets very hot and has burnt the board around it almost black. Also (in close proximity), an electrolytic capacitor is domed on its top end. Is this ever normal?

I suspect that a sensor failed and that this led the controller to repeatedly send a signal to the peripheral until it burned it out. The control board may be damaged too.

If someone is willing to provide some serious help so I can fix this, I will go the extra mile to provide circuit diagrams, pictures, etc.

I have basic knowledge of analog and digital electronic circuits and have designed and built some simple gadgets, but no electronic troubleshooting experience. With a little expert guidance I would like to find the bad transistor or whatever if possible. I have been out of work for some time and need to fix this at minimal cost. Please help!

Thanks!

[seanc]

Re: Control Board Failure

Hello! Could you tell us what this control board is for?

No, domed caps are not ever normal and it's likely that the hot resistor is cooking it, or it is causing the resistor to cook or a combination of both.

What value, series and model is the capacitor, what about the rest of them?

Can you please post clear pictures of the board, front and back, in 2000x2000 maximum size, attached to the forum using the "manage attachments" function.

[jetadm123]

Re: Control Board Failure

Is anyone up for a real troubleshooting chalenge?

I didn't know where to put this, but I thought you TV geeks might want to test your skills. I suspect problems with a digital controller board of a major item in the home (not a TV or computer), but I am almost certain that the problem originated with one of the peripheral devices (which has been acting up for years). This board stores events and they all point to this same peripheral.

I have tried forums that specialize in this item, but they all want to take the easy way out and have me replace the whole item, or swap out one or more $200 components by trial and error.

On the Control Board, one resistor gets very hot and has burnt the board around it almost black. Also (in close proximity), an electrolytic capacitor is domed on its top end. Is this ever normal?

I suspect that a sensor failed and that this led the controller to repeatedly send a signal to the peripheral until it burned it out. The control board may be damaged too.

If someone is willing to provide some serious help so I can fix this, I will go the extra mile to provide circuit diagrams, pictures, etc.

I have basic knowledge of analog and digital electronic circuits and have designed and built some simple gadgets, but no electronic troubleshooting experience. With a little expert guidance I would like to find the bad transistor or whatever if possible. I have been out of work for some time and need to fix this at minimal cost. Please help!

Thanks!

First of all, no disrespect, but what's with all the mystery? Why don't you just come out and tell us what "it" is along with the model number and some photos. Being vague is not going to win you any friends here. You're asking for "serious" help on a forums website? The help here is FREE and before anyone commits their valuable time to help you, you're going have to be forthcoming as to what you want to repair.

[sburtchin]

Re: Control Board Failure

I was not trying to be vague or mysterious, but I have a bad habit of overwhelming people with information (and scaring them off). Having been given the “easy way out answer” on 5 previous forums I was trying to provide no more information than necessary to answer just one question, namely if anyone was willing to see this to the end. Also, I was afraid if I mentioned "flood" I would get the standard answer. I paid almost $1300 for this and it matches my dryer. I'm not ready to throw in the towel that easy. Your forums have no “Miscellaneous” categories, so I wasn't sure if anyone wanted to venture outside the established forum topics. Having received the answer I was hoping for to my first question, I am ready now to invest the additional time to provide all the details.

Please excuse the late reply. I am still dealing with recent flood damage, and both my car and truck developed serious problems (brakes and fuel pump) at the same time. It apears that at least 3 separate problems with the car's brakes all developed within a few weeks. Still working on that.


DETAILS ABOUT THE APPLIANCE:

Maytag Neptune Front Loading Washer
Model (p) MAH5500BWQ
Serial NO. (S) 74793793ZY
Style (Y) Y7909216
Machine Control Board Number: 60C21280302, Software Version: 11
Motor Control Unit Model: AA20630 Rev: 04
This machine is referred to as the “LED Washer” in the service manual.

The MCB sits at the top of the washer behind the membrane pad and LED display. The MCU and discharge pump with its electronics is about 2 inches above the floor. The door latch assembly and other sensors and actuators and the drum motor remained dry in the recent flooding. The MCB keeps track of the last 99 non-critical events (called “Help Codes”) and the last 99 critical events (called “Service Codes”) in non-volitle memory.

This machine is only about 8 years old.


REFERENCE MATERIAL:

Here is a link to the repair manual: 16010061 Maytag Neptune Washer MAH3000 MAH4000.pdf. Pages 106 thru 157 are specific to my machine. No circuit diagrams of the logic circuits or the MCU that I have been able to find.

There was a class action lawsuit in Illinois Maytag® Front-Load Washing Machine Settlement about failures of the door latch and circuit boards. This machine is long past qualifying for benefits.


THE PICTURES:

MCB_Assy.JPG (MCB complete w/ backplate removed)

MCB_Front.JPG, MCB_FrontLeft.JPG, MCB_FrontRight.JPG

MCB_Back.JPG, MCB_BackLeft.JPG, MCB_BackRight.JPG

MCB_Close.JPG, MCB_CloseSunLit.JPG (closeups of obvious damage)

MCU_ID-tag.JPG, MCU_Front.JPG, MCU_Inputs.JPG

As far as I can tell the circuit boards are all just 2 layers. I could not find any internal traces.


THE TRIGGER EVENT:

Two years ago my basement flooded with about 5 or 6 inches water; enough to submerge the Motor Control Unit and discharge pump assembly. This washer performed flawlessly following that flood. Recently it flooded again with 10 inches water. This time I think the washer was turning valves on and off while the water was rising, and again when the flood water was going down because I could hear water running. Nothing additional got wet in the second flood.


SYMPTOMS & DIAGNOSTIC CHECKS:

Since then all the front panel lights seem to behave normally, but when I press Start it just humms quietly for a few seconds and nothing happens. A few seconds later it flashes "do" (door open), and sometimes it eventually flashes "FL" (failed lock). I tried to dry it with fans. That didn't work! There was a lot of other flood damage to deal with, so the MCU and discharge pump electronics remained wet about a week until I had time to dry them with a hair dryer. This condition was immediate, ie. no additional problems developed as a result of the MCU and discharge pump electronics remaining wet.

I've taken off the rear, top and front pannels, and ran some of the diagnostics, and here's the details:

Help Code.....Cycles Ago.........Service Code.....Cycles Ago
....19..................0......................04. ..................0
....47..................0......................17. .................56
....16..................2......................17. .................--
....40..................2......................17. .................--
....16..................3......................17. .................--
....19..................3......................17. .................--
....16..................5......................--
....13..................6
....19.................10
....--

Code key (see service manual for detailed explanations):
Help 19 - Power Down
Help 47 - Door did not lock
Help 16 - Spin suds lock
Help 40 - Motor running & door not locked
Help 13 - Low speed unbalance
Service 04 - Door fails to lock
Service 17 - Door switch not seen open since last final spin
"--" - No previous Help/Service code exists, OR the problem occurred more than 99 cycles ago

Note the flurry of problems occurring in just the last ten cycles! I have never placed a service call for this machine, so I know that these lists are complete. There are just two of us, so the Service Code 17 has been occurring over several years. I remember some of these events. No service warning was given, and I was allowed to continue.

Membrane Pad Check: ........Passed
Board Input Test: ..............Passed, except Fails "Latch Position" test
.......................................(shows "L0" even when I manually trip the switch)
Board Output Test: .............Fails everything I can see/hear (w/o VOM)
Fuse on Motor Control Board: OK

I tried everything that could be done in service mode (without using VOM) but could not make anything happen.

I removed the connectors from the door latch assembly and made some checks:
Door Lock/Unlock Switch: OK (0.4 ohm closed, infinity open)
Door Lock/Unlock Solenoid left pin (black wire) to common (white wire): 58 ohm
Door Lock/Unlock Solenoid right pin (yellow wire) to common (white wire): 61 ohm


On the MCB, "R102" gets very hot and has burnt the board around it almost black. Also, "C100" is domed on its top end. I removed Q2, R102 and C100. R102 measures 67 ohm now. C100 is an open circuit.

C100 should be 47uF 35v.

It is not obvious from the picture, but R102 connects directly to Q2. I could find no traces on the front side of the board associated with the Q2 circuit.

The markings on C100 (& C27, C34, C36) are:
SURGE
(M) 85º C
0114H

The other elecrrolytic caps are "0127H".

The markings on Q2 are:
MPS
A06
119

The caps on the MCU are made by Rubycon and have “CE 85º C” and “U S A” printed on them.

The connector terminals on the Lower Tub Displacement Switch and on the Pressure Switch (just the two center ones) have a lot of corrosion and thick foam-like mineral deposits on them.


QUESTIONS:

Can I assume the Door Lock/Unlock Switch and Door Lock/Unlock Solenoid are OK?

If you can tell me which lead is which and PNP/NPN on transistor "Q2" I can test it.

When the manual says to check the voltage between P1(5) and P8(2) I assume this means connector P1 pin 5 to connector P8 pin 2, but do I check this with the connector attached to the board, or do I check the board pins / connector contacts with the connector pulled off?

[retiredcaps]

Re: Control Board Failure

If you can tell me which lead is which and PNP/NPN on transistor "Q2" I can test it.

1) Did you replace the domed capacitor yet?

2) What is the part number for Q2? For transistors, I do a simple test for a short. Number the pins 1, 2, and 3. Test the resistance between 1-2, 1-3, and 2-3 "in circuit". Any reading under 30 ohms suggests the transistor is shorted and needs to be verified by desoldering the transistor and retesting out of circuit.

[jetadm123]

Re: Control Board Failure

Q2 is a MPSA06 NPN transistor. Spec sheet below. Not sure about the value of the surge caps.

[retiredcaps]

Re: Control Board Failure

You can test the transistor like I wrote above. 1-2, 1-3, and 2-3. Or E-C, E-B, B-C.

[Dgtech]

Re: Control Board Failure

If you do not know how to check for capactor markings to tell what the value is, google it and then apply that method to your situation. If you dont know how to solder, do the same thing. Once you have both of those covered, then seek out a cap with the similar value then remove the old one and replace it with the new one by way of soldering procedures. After this is done then place the boards back into the unit and give it a try. If it doesnt work then take it to someone who can troubleshoot it for you. I could go into how to test a transistor but I dont really know if you're up to the challenge. It's hard enough to get the capacitor value from you. We'll keep it simple, one thing at a time. The cap may just fix the damn thing. Dont make it harder than what it is. If you found a defective component, there is a problem that needs rectification. Let us know once this has been addressed. Thanks.

[sburtchin]

Re: Control Board Failure

Q2 has an open emitter. I think the Q2 circuit is for voltage or current regulation, please correct me if I am guessing incorrectly. So can I substitute any NPN with similar hFE and as good or better power dissipation?

What about the value of R102? Do you think it was 67 (or 65) ohms before it cooked? The band that is light brown now has the same lustre as the gold bands on the other resistors, however the band next to it had a patch of green on it's bottom side, which I don't think makes sense in this circuit if the light brown band was the tolerance.

I could go into how to test a transistor but I dont really know if you're up to the challenge.

It has been a while since I studied this stuff, but I can assure you that I can pick it back up very quickly.

It's hard enough to get the capacitor value from you.

I know my second post was a lot to digest, but it was there:

C100 should be 47uF 35v.

The cap may just fix the damn thing. Dont make it harder than what it is.

Can't argue with that. Well, the cap and the blown transistor, and maybe that cooked resistor. After I get advice on the condition of that resistor I'll solder things back together and post back the results.

[Dgtech]

Re: Control Board Failure

The resistor may be good. Higher wattage can stand a little heat from time to time.

[dbritton14]

Re: Control Board Failure

On replacing the transistor:

So can I substitute any NPN with similar hFE and as good or better power dissipation?

Yes, BUT transistors with the MPS prefix are Darlington-emitter transistors. Kind of like two transistors in one and provides very high, stable hfe. As the MPSA06 is easy to find, I would go back with that. Otherwise, ensure that whatever replacement you use is also Darlington. A regular general purpose NPN won't work or at least won't work well.

As for the resistor, how sure are you the value was 65/67 ohms? (BTW- the difference between 65 and 67 ohms wont matter to that transistor) If the value was 65 ohms, then it's color bands should have been Blue, Green, Black.

Can you tell if the cap was in circuit with Q2? I'm assuming a bypass cap to ground?

A side note: A good way to test transistors is to buy a multimeter with a diode check feature. Use it to test the N-P and P-N junctions.

[sburtchin]

Re: Control Board Failure

The resistor may be good. Higher wattage can stand a little heat from time to time.

It was hot enough to melt (or almost so) the solder on the opposite side of the board (see picture in previous post). But I guess these things are probably put together at much higher temperatures than that.

As for the resistor, how sure are you the value was 65/67 ohms? (BTW- the difference between 65 and 67 ohms wont matter to that transistor) If the value was 65 ohms, then it's color bands should have been Blue, Green, Black.

(and gold) My digital meter from Harbor Freight says it's 67 ohms (after I subtract the 0.8 ohms in the test leads). The second band from the left (Q2 end) had a little patch of green on the underside, hence my suggestion that it might be 65 (but it might have been 45 or 85 before the heat damage). Rechecked it again on my BK analog meter, and it reads 65 ohms on that meter. The color bands are now (from left) light brown, light gray (w/ patch of green), powder blue and black. I hoped there might be a conversion chart between cooked colors and original colors. Not surprised that gold would become black, but didn't expect blue to become light brown.

I made a diagram for the Q2 circuit (see attached). I am pretty certain it is correct. This should shed some light on what is reasonable for R102. The repair manual says the output of this circuit is +24v. I am guessing C100 was there to protect the emitter from back EMF from the switched load, so (with C100 open) I am seriously wondering whether the flood had anything at all to do with the failure other than speeding things up a little. With the open emitter, the only other path to ground for R102 was through D12, and sure enough, the diode check shows a 30mv drop in both directions.

[jetadm123]

Re: Control Board Failure

I figure that if C2 would vent as shown in your photos and with R102 overheating like that, it would be a common problem and there would probably be many complaints of it on internet. No complaints or others having the same issues, right? So, let's assume the flood cause some surge of power to vent C2 and damage Q2. Start by measuring the output voltage of the bridge rectifier (CR1). If no DC output, then CR1 could be bad. Now measure the AC input. If the input is also zero, then the transformer could have shorted out.

Also remember that you're making measurements in circuit, where surrounding components could affect your readings. Ideally, you want to remove the components for accurate testing. If your components still show failed, then go to digikey.com and order new parts (they're cheap, so order a few of each) and replace the defective components. With the new parts in place, look for the 24V output at Q2.

If there was some type of surge, then other portions of this board could have been damaged, possibly making your board beyond economical repair.

[tmwalsh]

Re: Control Board Failure

Is is possible there are 'out of balance' sensors that are mounted further down in the chassis such that they were being flooded? It looks from the 1st two pictures and your diagram that the circuit was simply over loaded. Flood waters make good conductors.
C2 is totalled. Hard to say about the MPSA06. Do U4 and U7 have any connection to this power circuit? From the picture, the labelling on the top of the two IC's seems 'brownish', as if they'd been over heating.
As noted above, the cap is cheap, the transistor is cheap, and you could get a couple resistors of each value, all for less than $10. Why not? I might even replace the full wave rectifier, CR1, as they can fail from overload also, and are less than a buck.
I have done similar with my almost 20 year old Kitchen Aid dishwasher. It has cabinet wood in the door panel, and one of the 1st membrane control panels. I keep seeing the words NLA whenever I look for parts. Next time it dies, out it goes. The timer-sequencer was ~$80, and available only as special order from one place when I replaced it about 10 years ago. I have even taken the membrane assembly apart. Ugh.
tom

[sburtchin]

Re: Control Board Failure

I didn't see other complaints of this burnt resistor, but maybe I just didn't use the right search criteria. There is an overwhelming volume of control board failure complaints for this machine and a class action suit about it (see my second post) related to the door latch which is directly driven by this circuit. All the appliance forums give the pat answer to replace the whole board and usually the door latch assembly too (which they sell). I suspect this in particular is common because the serviceman at Miller's Coral told me he once repaired a Neptune washer by replacing a cap, transistor and resistor, and maybe something else from a repair kit he bought on eBay for $25. Sound familiar? On his the transistor was split open.

I'm thinking a lot of little surges. Notice that problems with the door latch (and unbalance switches) started ocurring before the flood. It was sort of a slow failure. I didn't smell the resistor burning until several days after the flood. Once that cap died the transistor had to bear the brunt of any surges.

The unbalance switches remained above water, but the motor controller board and the discharge pump would have been submerged. I'm not sure if they have any connection to this circuit.

The loss of output from this circuit would explain at least some of the diagnostic failures. I can't find anything else on the board that looks burnt, so I'm crossing my fingers. I put my order into Digikey today. In the mean time I have quite a bit of reassembly to do.