Set Appliance State:

Isolate Mains Power to appliance as per TOPs P4
Set Multimeter to DC Volts Set meter to measure DC Volts
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:

Measure the DC voltage between pin 4 (grey) on connector X20 and a suitable earth.
Expect a reading of approximately 22 Vdc.
Note:
Each pin on the PCB connector is numbered.