2 ] Led Does Not Turn On; Led Doe Not Turn On. - Brother TD-4000 Service Manual

[ 2 ] LED does not turn ON.

LED does not turn ON.
Or LED turns on temporarily.
power supply connected correctly?
Is the cable of SB PCB
lines in the cable broken?
the correct color connected?
Is the head cable connected
power supply PCB correctly?
Are the power supply PCB, DC8V
power PCB and main PCB
of the power supply PCB 24 to 26V?
Is the output of the pin (No.1)
output of the DC8V power
The SB PCB is defective.
Replace the SB PCB.
Is the cable of
Is the main power
switch ON?
Y
connected correctly?
Y
Are any of the
N
Is the panel cover
assembled correctly?
Y
Is the head cable of
correctly?
Y
Is the connector
(CN6)connected to the
connected correctly?
Y
Is the connector output
on the power supply
PCB 7 to 5V?
Y
Is the connector
PCB 7 to 5V?
Y
Are the key and LED
signals of CN16 normal?
Y
Are the output signals
from pin 3 and pin 4 of
CN16 normal?
Y
N
Correct the connection.
Turn ON the main power switch.
N
Correct the connection.
Y
Replace the SB PCB.
N
Re-assemble the cover correctly.
N
Correct the connection.
N
Correct the connection.
N
Replace the power supply PCB.
N
Replace the DC8V power PCB.
N
Replace the SB PCB.
N
Replace the main PCB ASSY.
IV - 4