Brother HL-1240, Service Manual

Page: 128 / 333

CHAPTER 6 TROUBLESHOOTING
6-18
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 Step Check Result Remedy
Supply voltage 1 Is the correct voltage present
at the outlet? No Inform the user that the correct
voltage is not supplied at the
outlet.
Power plug 2 Is the power cord securely
plugged into the outlet? No Plug the power cord securely
into the outlet.
Fuse (F1, F2) 3 Is the fuse blown? Yes 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.
Wiring 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? Yes Replace the AC power cord.
M-2 No DC power supplied
Possible cause Step Check Result Remedy
AC power
supply 1 Is AC power supplied between
connectors CN1-L and CN1-N
when the power plug is
plugged into the outlet? No Follow the same check
procedure of M-1 “No AC
power supplied”.
Wiring, DC load 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? Yes 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.
Low-voltage
power supply
PCB 3
PCB + lead pin - lead pin Voltage
Engine
P5-2 P5-3 Approx. 24V
P3-10 P3-9
Approx. 5V
No Replace the low-voltage power
supply PCB.
WARNING
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.