Thanks for the information Peter.
There are 3-Relays on the board and I removed the worst looking one.
However on close inspection and opening it up, it was perfect inside, now replaced with new. The diode across the coil I read as 5.6? on the test meter. After cleaning that capacitor and removing, I think I got a high value resistance, assumed it was OK and not knowing the value at the time soldered it back in.
The 230v/12v 12VA transformer on board had burn't the primary winding OC so I replaced that.
Certain areas of the board were blackened especially around the relays, leading me to remove one for investigation, however it looks like this black residue appears to follow the route of the embedded copper connections in the circuit board. Maybe these strips get warm since they carry the ac switching from the 16A relay contacts and cooling air is blown around to keep the inverter going over temp.
It has been in use for approx. 16 years and I am hoping to repair the inverter, since this is only the ac control board for the main inverter unit.
There are no wiring diagrams available, so I have been trying to draw one out, not easy since there appear to be 3-layers of connectons on board, and need to shine light through the board, still working it out.
I send you a couple more photos showing the 2-Current Transformers also on board.
Lots of time required.
Best regards
Gordon