Mitsubishi electric noise filter board blowing

[Northy303]

Hi,
I am going to investigate a mitsubishi PUHZ-ZRP140YKA that had a blown noise filter board, a new noise filter board has been replaced and blown immediately. I have contacted Mitsubishi and they tell me that it is a problem with the incoming power supply possibly voltage down the neutral.
I will check this first but after studying the wiring diagram and photos of our blown board it looks like power for the fan motors come off the nf board .
So my question is looking at this wiring diagram could the DC fan motors blow this nf board.
Thanks in advance.

[Tayters]

Yes, it does look that way.
Connector CNDC on the bottom of the noise filter as you point out comes from the gizmo indicated in the lower right hand side of the board, the high voltage supply for the fans, normally red and black wires 350V or a bit more DC.
If you haven't done so already, need to unplug the motors and test resistance between those wires, hopefully not a short circuit!

I've got a bit of info I'll send on general testing of BLDC motors to your email. Might end up in the spam folder.

Cheers,
Andy.

[Brian_UK]

If they are anything like some Daikins it is the fan motor blowing the boards.

[Northy303]

Thanks for the reply, I am going there with just a noise filter board and I am going to check the fan motors unplugged (thanks for the info andy) then I am going to run it up with the power from a working condenser unit same model and check all the boards.
Will let you know how I get on.
Matt

[Tayters]

Just in case you weren’t aware, Before unplugging anything on the high voltage DC side of things (fan motors, inverter parts) be sure to power the unit off for a few minutes before unplugging or else the high voltage can spark across the plug blowing the pin off the board and buggering electronics as well.

Good luck!