Technical data

Fault Isolation 4-63
The following three procedures show you how to checkout the Model 400t and 400dl
system components:
• Procedure 4-5 describes how to check the power supply and related FRUs.
• Procedure 4-6 describes how to check the Winchester disk power.
• Procedure 4-7 describes how to check the calendar battery.
Procedure 4-5. Power Supply Verification for the Model 400t and 400dl Systems
Note the following information about the power supply operation before you perform
this procedure:
• The power supply delivers dc voltages to the CPU board and disk drives when
you press the power-on switch on the front panel. The power-on switch acti-
vates the power supply by pulling low a signal line at Connector J004, Pin 8.
(The signal line is normally high when the supply is off.)
• When you power on the system, a relay within the power supply closes to route
ac voltage to the display monitor outlet at the rear of the system unit.
• The system fan, which is housed in the rear of the power supply, is not a sepa
-
rate FRU. If the fan doesn’t operate, you must replace the power supply.
You need a voltmeter and an ohmmeter to perform this procedure.
NOTICE: Before you replace the power supply or a related FRU, always
visually check the power supply harness and other FRU
cables for loose, broken, or pinched wires.
If you find a defective FRU, follow the removal and replace
-
ment procedures in Chapter 5 to replace it.
First, make sure that the system power is off and that the power cord is unplugged.
Then, remove the system cover. Now continue with the following steps.
1. If connected, disconnect the system from the network. If the system uses a net-
work connector, unplug it from the network wall outlet. If the system uses BNC
connectors to connect to the network, unplug them from the rear of the system unit.
This opens the loop in the network. To complete the loop while you are servic-
ing the system, use a barrel type BNC connector between the IN and OUT connec-
tors.