Philips M3921A Service Manual page 61

Chapter 5 - Troubleshooting
problems.
Condition
1. With external power
supply connected
the green
EXTERNAL
POWER indicator
on the front panel is
not lit.
2. The A1 fails to
power-up when the
ON/STANDBY
button is
pressed...with the
monitor connected
to external power
supply.
3. The A1 fails to
power-up when the
ON/STANDBY
button is pressed
with the monitor not
connected to
external power
supply.
Recommended Action
1. Ensure that the external power supply input (PS-120V
or PS-240V) is plugged into an operational AC outlet
of appropriate voltage and frequency.
2. Disconnect the power supply output cable from the
monitor. Measure the voltage across pins 1 and 4 of
output connector. If the open circuit voltage does not
measure approximately 17 ±3 V~RMS, replace the
power supply.
3. If the battery is severely discharged or shorted, the
EXTERNAL POWER indicator does not light. Connect
the external power supply to an AC outlet and to the
monitor. Allow the battery to charge for 30 minutes. If
the EXTERNAL POWER indicator still does not light,
replace the battery.
4. Inside the monitor, check the ribbon cable and ensure
that it is properly connected to the main PCB.
5. The EXTERNAL POWER indicator is embedded in
the keypad. Ensure that the keypad is plugged into
Main PCB. If the connection is good, replace the
keypad.
6. If the problem persists, replace main PCB.
1. Connect the appropriate external power supply (PS-
120V or PS-240V) to the monitor. Ensure that the
external power supply input is plugged into an
operational AC outlet of the appropriate voltage and
frequency. Ensure that the green EXTERNAL
POWER indicator is lit. If the indicator is not lit, follow
the steps described in Condition 1, above.
2. Ensure that the keypad is plugged into Main PCB. If
the connection is good, replace keypad.
3. If the problem persists, replace the main PCB.
1. First, follow the steps described in Condition 2,
above, to ensure that the monitor operates when
connected to an external power supply.
2. Check fuse F301 located on the Main PCB, near the
battery cable connector. Replace fuse if necessary.
3. Recharge the battery as directed in "Battery Charge"
on page 11. If the battery fails to hold a charge,
replace the battery.
4. If the problem persists, replace the main PCB.
Troubleshooting Guide
49