Service manual

PN 4237242C
4.5-2
SERVICE AND REPAIR PROCEDURES
AT POWER SUPPLY
4. Connect the power supply to the instrument:
r P1 connects to the floppy disk drive power connector.
r P2 connects to a cable from the lower chassis terminating at the AC Power/Vacuum
Relay card.
r P4 and P5 attach to the AT motherboard connectors P8 and P9.
5. Reconnect the ac power cable and turn ON the instrument’s power. Wait until the
instrument reaches the Main Menu. It is difficult to check power before connecting to
the motherboard, since the power supply requires a load before it turns on any supplies,
including the power for the fan.
Verification
1. Check voltages at any connector. A label showing a detailed pinout is affixed to the top
of the AT power supply and greater detail is also available from the System Interconnect
diagram (Chapter 6, Schematics and Block Diagrams). Even without a voltmeter, if the
system reaches the Main Menu after power ON, the +5, +12, and -12 V supplies must be
present.
r Red wires are +5 V
r Yellow wires are +12 V
r Orange wires are -5 V
r Blue wires are -12 V.
2. Replace the top cover.
3. Perform an SVP (Heading 5.1).