Set Appliance State:
Mains Power Off
Use Insulation Mat as required
Set Multimeter to AC Volts 
| WARNING! Mains voltage is expected during test, follow TOPs P4 live testing procedure |
Measurement:
Measure voltage across terminals marked L (live) and N (neutral) on connector X4 on main driver board.
Isolate as per TOPs P4
and refit as necessary