Set Appliance State:

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

Using either a socket and see or multimeter re confirm the polarity on the incoming mains supply to the appliance at connector X1 for the live and neutral terminals and X11 for
the earth connection.
Is the polarity correct?