Set Appliance State:
Set Multimeter to DC Volts 
Isolate Mains Power to appliance as per TOPs P4
Gain access to PCB (use insulation mat as necessary)
Disconnect display harness from display board
Gain access to PCB (use insulation mat as necessary)
Disconnect display harness from display board
| WARNING! - Mains voltage is expected during test follow TOPs P4 live testing procedure |
Measurement:
Test 1:
Measure the voltage between terminals 3 and 4 at the PCB connector.
Voltage should be approximately 5 Vdc.
Test 2:
Measure the voltage between terminals 3 and 2 at the PCB connector.
Voltage MUST be seen to fluctuate between 3 Vdc and 5 Vdc.
Test 3:
Measure the voltage between terminals 3 and 1 at the PCB connector.
Voltage MUST be seen to fluctuate between 3 Vdc and 5 Vdc.
If the voltages on Test 2 and 3 remain static then this is incorrect.
Note:
Ensure probes do not touch together during tests.
Measure the voltage between terminals 3 and 4 at the PCB connector.
Voltage should be approximately 5 Vdc.
Test 2:
Measure the voltage between terminals 3 and 2 at the PCB connector.
Voltage MUST be seen to fluctuate between 3 Vdc and 5 Vdc.
Test 3:
Measure the voltage between terminals 3 and 1 at the PCB connector.
Voltage MUST be seen to fluctuate between 3 Vdc and 5 Vdc.
If the voltages on Test 2 and 3 remain static then this is incorrect.
Note:
Ensure probes do not touch together during tests.
Isolate as per TOPs P4
and refit as necessary