Troubleshooting 3-9
5. This message will be displayed for approximately 10 seconds after AC power is lost. Once AC
power is restored, the system will power up provided the key switch is either ON or in the
"SERVICE" position. This condition does NOT require cycling of the key switch.
6. These three messages will cycle as the system retries to access the power supply.
7. This fault indicates a watchdog timer error has occurred. The watchdog timer is the Power Monitor
card microprocessor fault detector. If this fault occurs, the Display panel will contain the last
message written to the Panel by PDC or the O/S. The fans will not be running and the Display Panel
backlight will be out.
Display Panel Troubleshooting
The Display Panel is connected to the Power Monitor card via a ribbon cable. Use Table 3-5 to determine
the error condition and suggested action:
Key Switch Troubleshooting
The key switch is connected to the Power Monitor card via a ribbon cable. Use Table 3-6 to determine the
error condition and suggested action:
Table 3-5. Display Panel Troubleshooting
Symptom Cause Action
Backlight is on but Display Panel
is blank
No contrast control from Power
Monitor card
1. Replace PM card
2. Replace Display Panel
3. Replace ribbon cable
Display Panel data is dim Defective contrast control circuitry 1. Replace PM card
2. Replace Display Panel
Display Panel Data is garbled or
unreadable
Data not being correctly decoded by
Display panel
1. Replace Display Panel
Display Panel displays power
monitor messages, but does not
display O/S data
PDH not issuing messages to the
display panel
1. Replace System Board
Table 3-6. Key Switch Troubleshooting
Symptom Cause Action
System does not power up when
key switch is on (no error mes-
sages on Display Panel)
Key switch position not being
detected by the PM card, or the Key
switch is defective
1. Replace PM card
2. Replace Key switch
3. Replace Ribbon cable
Service position does not allow
Control B functionality
"SERVICE" position signal not
being detected by the Access Port
(AP)
1. Replace Core I/O Card
2. Replace System Board
3. Replace PM card
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