Comments on: Seeking motor controller for F&P MW512 washing machine

Question: Seeking motor controller for F&P MW512 washing machine

flabdablet — Thu, 29 Mar 2007 17:28:36 -0800

Please help me find a second-hand motor controller for my Fisher & Paykel Smartdrive MW512 washing machine.

I was very proud of my homebrew extended cold water supply hose, but the hose clamp on the machine end failed after about a year, accurately injecting a few litres of water into my Smartdrive MW512's electronic innards before popping off entirely and flooding the laundry floor.

I didn't realize that the electronics had been doused until I replaced the hose a day later and the machine failed to start; it had been plugged in all that time. Now the motor controller smells bad, the PCB features a very artistic pattern of burnt and corroded tracks, and assorted components have been so badly corroded that they snap off when gently brushed clean. Sigh.

I've disassembled, dried and reassembled the also-drenched front-panel board, but I think the motor controller has gone to God. Burnt trackwork aside, the PCB has an assortment of high-voltage electronics and proprietary microcontroller parts, and I have no faith that their magic smokes have remained unmixed.

Can anybody help me track down a replacement motor controller for less than the AU$160 RRP I've been quoted by Fisher & Paykel Customer Care? Second-hand is fine. I'm in East Gippsland, Victoria, Australia.

The motor controller has a big yellow sticker that reads

MOTOR CONTROLLER
PASS
P7CP
(bar code)
420786⁰⁰³³³⁶
230V
24/08/2005
10:48

By: FauxScot

FauxScot — Thu, 29 Mar 2007 17:49:09 -0800

Ick! Sorry! What a disaster.

My experience in fixing stuff like this says to bite the bullet and go with the manufacturer's replacement part.

( I've got a Thermador dual oven with a clock/controller that I know one day will die a horrible death, leaving me with a $5,000 US hole in the cabinet. I'm tempted to buy a replacement now, prophylactically. Sometimes, there is just no good alternative to the manufacturer.)

Really, there are so many design decisions involved in a motor controller that I'd be loathe to buy anything else, in the unlikely event you could buy ANYTHING to work.

Just a few of the issues... motor constants (coil resistance, torque, RPM, BEMF constant). How is speed measured (tach, BEMF, current)? Control method (PWM, phase angle control)?

There's probably a PID running in there, too, and those are tuned to specific mechanical and electrical time constants, inertias, etc.

You've got mechanical issues too... how to mount, connect, etc. Safety must factor in, too.

The $160 sounds like a reasonable price for a motor controller.

Good luck... ( FWIW, I think you're pretty brave to even attempt fixing it on your own! )

By: flabdablet

flabdablet — Thu, 29 Mar 2007 18:02:42 -0800

Just to be clear: I wouldn't even consider using something other than the manufacturere's original part; it's a very specialized microprocessor-controlled machine that drives a direct-drive DC motor. I'm hoping to track down a second-hand one.

By: nonmyopicdave

nonmyopicdave — Thu, 29 Mar 2007 21:15:37 -0800

Whoa, that's going to be a long shot!

You might try posting something over at the Appliance Samurai forum.

By: flabdablet

flabdablet — Thu, 29 Mar 2007 22:42:09 -0800

This is AskMe. It has a history of making long shots work :-)

And I already have a post open with the Samurai, which has so far only resulted in a suggestion that I check eBay, which of course I did before posting anywhere, and continue to do.

I live in hope :-)

By: flabdablet

flabdablet — Thu, 29 Mar 2007 23:46:43 -0800

It's not going to happen, is it.

I've cracked, and ordered a new one direct from F&P; so I've stopped living in hope, and now I'm living in poverty instead. Which is almost as good, I suppose :-)

Thanks to all who gave this some thought.