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)
Attach a crocodile clip to the rectification lead
WARNING! - Mains voltage is expected during test follow
TOPs P4 live testing procedure
Mains Power On

Measurement:

Reset appliance as necessary.
Allow boiler to complete its self check.
Set the appliance to t6 - click here for information on how to set the boiler test modes.
Measure the voltage between the green wire
on X4 marked 11.1 and the crocodile clip.
Approx 40V AC should be measured.