Brother International HL-720 Service Manual - Page 73

Malfunctions, No AC power supplied

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3. TROUBLESHOOTING OF MALFUNCTIONS Always turn off the power switch and unplug the power cord from the power outlet before accessing any parts inside the printer. In case that you analyze malfunctions with the plug inserted into the outlet, such as checking the supply voltage, special caution should be exercised even if the power switch is OFF because it is one way off type. Touching the power supply PCB may cause to struck you by electricity. When carrying out the countermeasures for malfunctions described in this section, make sure to check connectors for contact failure before measuring the voltage at specified connector pins. M-1 No AC power supplied Possible cause Supply voltage Power plug Fuse (F1) Wiring Step 1 2 3 4 Check Is the correct voltage present at the outlet? Is the power cord securely plugged into the outlet? Is the fuse blown? Unplug the power supply plug. Is there a broken wire between the AC input connector of the lowvoltage power supply and the power plug? Result No No Yes Yes 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 low-voltage power supply PCB. Check if there is a short circuit somewhere in the AC power supply line. Replace the AC power cord.

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3.
TROUBLESHOOTING OF MALFUNCTIONS
Always turn off the power switch and unplug the power cord from the power outlet before
accessing any parts inside the printer.
In case that you analyze malfunctions with the plug inserted into the outlet, such as
checking the supply voltage, special caution should be exercised even if the power
switch is OFF because it is one way off type. Touching the power supply PCB may
cause to struck you by electricity.
When carrying out the countermeasures for malfunctions described in this section, make
sure to check connectors for contact failure before measuring the voltage at 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)
3
Is the fuse blown?
Yes
If the fuse blows again
immediately after
replacing low-voltage
power supply PCB.
Check if there is 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.