Set Appliance State:
Mains Power Off
Set Multimeter to AC Voltage 
Purge Switch in NORMAL position
HW Switch in OFF position
CH Switch in OFF position
HW Switch in OFF position
CH Switch in OFF position
| WARNING! Mains voltage is expected during test, follow TOPs P4 live testing procedure |
Measurement:
Measure the Voltage across one of the Black wires (marked 9V) and the Yellow wire (marked 0) on the Main PCB Connector marked PL7.
Repeat the test using the other Black wire (marked 9V) and the Yellow wire on the Main PCB Connector marked PL7.
A reading of approximately 9 Volts should be measured on both Black wires.
Repeat the test using the other Black wire (marked 9V) and the Yellow wire on the Main PCB Connector marked PL7.
A reading of approximately 9 Volts should be measured on both Black wires.
Isolate as per TOPs P4
and refit as necessary