Mitsubishi Electric EHST20C-YM9B+PUHZ-SHW112YHAR3 U9 alarm

Hello everyone.

I have a trouble with finding solution to the problem with this unit.
Received a call from the customer with U9 alarm. As manual says, there could be a problem with Power PCB or Converter PCB.
When the PCB box was open, it was clear that the PCB was out of service - some parts that are brazed to the PCB were on the bottom of the PCB box. The Power PCB was replaced. Then the most confusing part started. The unit does not start the compressor, but starts fans for about 1-2 seconds at full speed and then stops for 3-5 minutes. There is not any error code. The resistance of the compressor was controlled and ohms were OK according to manual, Inverter PCB was controlled with inverter checker - no problem. What could cause this kind of problem? Maybe someone had any familiar cases before?

Have you tried to obtain the detailed codes of U9 error?
The manual says:
To find out the details about U9 error, turn ON SW2-1, 2-2, 2-3, 2-4, 2-5 and 2-6 when U9 error occurs.
To find out the detail history (latest) about U9 error, turn ON SW2-1, 2-2 and 2-6.

http://sftp.mitsubishielectric.es:80...co/OCH526C.pdf

page82

I think the power board is bad