Set Appliance State:

Set Multimeter to AC Volts Set meter to measure AC Volts
CH Demand
Isolate Mains Power to appliance as per TOPs P4
Operating Switch in Heating & Water position
Gain access to PCB (use insulation mat as required)
WARNING! - Mains voltage is expected during test follow
TOPs P4 live testing procedure
Mains Power On

Measurement:

Is there Mains Voltage across connector X6 (Blue) and (Brown) on the Main Driver Board?