Set Appliance State:

Isolate Mains Power to appliance as per TOPs P4
Set Multimeter to DC Volts Set meter to measure DC Volts
CH Demand
Gain access to display PCB
Disconnect X1 from the display PCB
WARNING! - Mains voltage is expected during test follow
TOPs P4 live testing procedure
Mains Power On

Measurement:

Measure the voltage between pin 1 (orange)
and pin 5 (white) at X5 on the display PCB.
Voltage should be 20V DC or greater.