Re: Motor Wiring Help Please!

prettyboy988-google@xxxxxxxxx wrote:
James,

I bought a Neptune washer model MAH5500BWW in 2001. It has been working
until this Monday. The motor does not spin at all. BTW, I totally
missed out on the class action lawsuit since I hadn't had any problems
with the washer. An of course, I don't have the warranty anymore.

So I opened the main control board cover and found a wiring diagram and
some diagnostic test instructions. I ran the test and traced it down to
the motor control board (located at the lower right bottom from the
front panel), and a 10Amp fuse was blown. The instructions states that
"If the motor does not run: Check the 10 amp fuse located on the
control board, either visually or with an ohm meter. If bad, replace
motor control/wire harness assembly completely." I checked the maytag
website and the part costs $174.99 + tax + shipping. After reading all
the problems with the neptune washer on the net, I am not sure if I
want to reinvest about $200 on this thing, which may fail with other
problems sooner or later.

With my understanding in electricals, a fuse is supposed to the protect
the circuitry. So why in the world do you need to replace the entire
assembly if just the fuse is blown. I went to the radio shack and
bought a 10 amp fuse, soldered it in, ran the test again, same failure.

With your experience in fixing a neptune, can you shed some light or
give me any suggestions. I'd be much appreciated.

Best Regards,
PB



Well so far I've picked up two Neptunes, both with the exact symptoms you describe. The first one I was lucky and the fuse was not blown on the motor board and resoldering a bunch of cracked joints got it up and running.

The next one the fuse was also not blown, but several of the MOSFETs, and a couple of the driver chips had craters blown in them. I replaced those parts and then discovered that the large custom chip was also fried so I ended up replacing the motor board, got lucky and a friend had an extra one through a screwup of the warranty service on his but you can order them from repairclinic.com.

You can try replacing any shorted mosfets and driver IC's and you may get lucky, or you may find that the control chip is fried. It's unfortunate that they didn't incorporate any sort of isolation or protection so if a mosfet shorts then high voltage can trace right back into the low voltage logic. The fuse blows to prevent anything from catching fire, but logic chips can be fried an order of magnitude quicker. What I would do is remove any shorted mosfets and their respective driver chips, then apply power and check for 5V across the power and ground pins on the control chip. In my fried one it was holding the voltage down to around 1V. You could also check for signs of life from the outputs of the chip, a scope will help here but be sure you power the board from an isolation transformer if you try that.
.

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