Repair Power Module for washing machine

[Malcolm Fowler]

Hi,
I have a Fisher & Paykel washing machine with Smart Drive (?) The main
motor power module has "spat the dummy". The fuse blew and two diodes
on the input bridge rectifier self destructed. No replacement modules
are available. Can anyone give me a clue as to the most likely cause?
Basically the mains is rectified and then passed on to what appears to
be a 3 phase inverter motor controller. The motor may have shorted but
it looks OK and I would have expected the diodes on the control side
to have blown - they are OK. I am suspicious of the mains filter
capacitor (10mfd 250v) but it tests OK as 10mfd when removed from the
circuit - but could it still be an effective short at mains voltage?
Any suggestions would be appreciated

 

[selldastuff]

I would suspect that a cap that would be a short at mains voltage would very
quickly burn/melt or blow the mains fuse.

Perhaps this site may give some ideas:
http://www.irf.com/product-info/appliance/washer.html

or if not, then....

http://www.angelfire.com/electronic/antifisherandpaykel/

 

[budgie]

Hi,
I have a Fisher & Paykel washing machine with Smart Drive (?) The main
motor power module has "spat the dummy". The fuse blew and two diodes
on the input bridge rectifier self destructed. No replacement modules
are available. Can anyone give me a clue as to the most likely cause?
Basically the mains is rectified and then passed on to what appears to
be a 3 phase inverter motor controller.

It certainly is on our SD603.

The motor may have shorted but
it looks OK and I would have expected the diodes on the control side
to have blown - they are OK. I am suspicious of the mains filter
capacitor (10mfd 250v) but it tests OK as 10mfd when removed from the
circuit - but could it still be an effective short at mains voltage?

IMHO it would smoke.

Any suggestions would be appreciated

Most common failure appears to be one of the six FETs. If it fails short (most
often the case), this takes out its opposite number on the next half cycle of
drive. This then presents a rail-to-rail short and the fuse (at least) goes
west.

If you are determined to fix it, I recommend:

1. Use a lamp (say 100W) in series with the machine. That way any hard shorts
will be immediately obvious and non-destructive.

2. Be aware that both DC rails are live.

3. The micro drive to all six FETs should be checked. Often this is the
underlyiing cause. (Unfortunately due to 2 above this is difficult with the
average CRO unless you also have a 1kW isolation transformer available.)

If your machine is a SD603 or one of its siblings, I may be able to advise
further.