Specifications

Power Supply Verification for the Model 400t, 4254 and
400dl Systems
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Note the followin information about the power supplyoperation before you
?perform the troub eshooting steps:
The power suppl delivers dc volts es to the CPU board and disk drives
x
‘%
when you press t e Power+n swtc on the front panel. The power-on
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switch activatesthe power supplyby ulling low a si nal line at Connector
7!J(H)4,Pin 8. (The signal line is norms Iyhigh when t e supply is off.)
When you
r
wer on the system, a relay within the power supplycloses to
ro@e ac vo tage to the display monitor outlet at the rear of the systemunit.
The system fan, which is housed in the rear of the power supply,is not a
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separate FRU. If the fan doesn’t operate, you must replace the power
supply.
Perfrom the followingsteps to troubleshoot the power supply. Youneed a volt-
meter and an ohmmeter to perform these steps.
NOTICE: Before ou replace the power supplyor a
relatedhU, ahva~checkthe~wersup
ly harness and ot er FRU cab es for loose,
Eroken, or pinched wires.
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4-16
Troubleshooting