Set Appliance State:

Mains Power Off
Mode selector switch to Off/Reset position
Set Multimeter to AC Volts Set meter to measure AC Volts
Use insulation mat as necessary
WARNING! - Mains voltage is expected during test follow
TOPs P4 live testing procedure
Mains Power On

Measurement:

Measure the voltage between live, connection 5 (brown wire) and neutral, connection 7 (blue wire) at connector M16 on the main PCB.
Note:
Connections are numbered top to bottom.