Led Light Does Not Turn On - Brother PR655 Service Manual

Failure Investigation for Electronic Parts
Is the LED lead properly connected
to the left side of the LED PCB?
Is the LED lead properly connected
to connector CN3 on the main PCB?
Is the LED lead properly connected
to the right side of the LED PCB?
Is the LED lead properly connected
to the left side of the LED PCB?
When the left side of the LED PCB is replaced
with a new one, does it light normally?
Does the LED light turn ON when the LED lead
is replaced with another one?
When the right side of the LED PCB is replaced
with a new one, does it light normally?
Is the voltage between pins 3 and 4 of the
connector CN26 on the main PCB 23 to
27V, when the power is turned ON?

LED light does not turn ON.

Is the lamp set to "ON"?
Y
Y
Y
Y
N
N
N
Y
Change the main PCB.
5 - 18
N
Set the lamp to "ON".
N
Connect it properly.
N
Connect it properly.
N
Connect it properly.
Y
Change the left side of the
LED PCB.
Y
Change the lead wire assy:
LED.
Y
Change the right side of the
LED PCB.
N
Change the power supply
PCB unit.