Servis M3108W keeps tripping house RCD

Hello,

I wonder if you could help me. I have a Servis Automatic 800, model number M3108W and recently it started tripping the RCD when it starts to run. The machine is from 1998 and apart from changing the seal and bearings six years ago has given no trouble up to now.

The machine powers on (red light on) and when you click it onto a program (rotary dial) there is a hissing noise for a second then the house RCD trips.

So far I have;

1) taken the back and top off the machine,
2) removed the motor and inspected it, all seems fine,
3) removed the heater element and inspected it, again no obvious faults.
4) inspected all wiring for dampness and broken insulation/ corroded connectors, again fine
5) have also started machine up with heater element, motor and waste water pump disconnected and it still trips out
6) have also disconnected electrical components (temp sensors, switches etc) one by one, every component I could disconnect and the machine still has power and started the machine and it still gets as far as just starting a program and then the RCD trips.

There is a circuit board bolted to the rear corner of the machine in a plastic cover (partly open) and there is evidence of water splashes on this. Could a water damaged circuit board cause these symptoms?? The board appears undamaged and no burnt out components etc, no corrosion however on the circuit.

Any ideas would be most appreciated.

many thanks

regards

John