Malfunctions - Brother HL 1240 - B/W Laser Printer Service Manual

CHAPTER 6 TROUBLESHOOTING
6.

MALFUNCTIONS

When taking countermeasures for malfunctions as described in this section, check connectors
for contact failure before measuring the voltage at the specified connector pins.
M-1 No AC power supplied
Possible cause
Supply voltage
Power plug
Fuse (F1, F2)
Wiring
M-2 No DC power supplied
Possible cause
AC power
supply
Wiring, DC load
Low-voltage
power supply
PCB
If you analyze malfunctions with the power plug inserted into the power outlet, special
caution should be exercised even if the power switch is OFF because it is a single pole
switch.
Step Check
1 Is the correct voltage present
at the outlet?
2 Is the power cord securely
plugged into the outlet?
3 Is the fuse blown?
4 Unplug the power supply plug.
Is there a broken wire between
the AC input connector of the
low-voltage power supply and
the power plug?
Step Check
1 Is AC power supplied between
connectors CN1-L and CN1-N
when the power plug is
plugged into the outlet?
2 Turn off the power switch and
disconnect the P3 and P5
connectors on the engine PCB.
Turn on the power again.
Measure the voltages between
the terminals. Do the
measured voltage satisfy the
prescribed valued in the table
below?
3
PCB + lead pin - lead pin
P5-2
Engine
P3-10
Result
No
No
Yes
Yes
Result
No
Yes
No
Voltage
P5-3 Approx. 24V
Approx. 5V
P3-9
WARNING
6-18
Remedy
Inform the user that the correct
voltage is not supplied at the
outlet.
Plug the power cord securely
into the outlet.
If the fuse blows again
immediately after replacing the
low-voltage power supply PCB,
check that there is not a short
circuit somewhere in the AC
power supply line.
Replace the AC power cord.
Remedy
Follow the same check
procedure of M-1 "No AC
power supplied".
Turn off the power switch,
reconnect the connector and
turn the power switch on again.
If the protector circuit is
activated, check the connector,
the wiring from the connector,
and the DC load.
Replace the low-voltage power
supply PCB.