IBM 7012 300 Series Installation And Service Manual page 33

Step 4
(from Step 3)
This problem can be caused by one of the following FRUs:
Front fan
Rear fan
Note: It is likely that the voltage regulator has failed when power is supplied and the power
Voltage regulator card (Model 39H)
System planar (Models 340, 34H, 350, 355, 360/36T, 365, 370/37T, and 375 , 380, 390,
397 if the rear fan is failing)
Power supply.
The power supply will not stay on if it does not sense the rotation of the cooling fans.
Note: The power supply does not sense the fans that cool the disk drives if the fans have
1. Set the power switch on the system unit to Off.
2. Test each fan by connecting a new fan. Refer to the "Rear Fan" removal procedure on
page 3-45 and the "Front Fan" removal procedure on page 3-46.
3. Set the power switch on the system unit to On. Wait 10 seconds before answering the
following question.
Did the power-on light come on and stay on?
NO
YES
light is on for one second or less. The same symptom will occur when the voltage
regulator is not connected to the CPU card.
only two wires and comes on independent of the operation of the front or rear fans.
These fans will not cause the power supply to shutdown.
When the front or rear fans are not connected or are not operating, the power supply
will usually power on for approximately three seconds before shutting down.
Repeat this step until the defective fan is identified or all the fans have been
tested.
One of the remaining FRUs is defective.
To test each FRU, exchange the FRUs in the following order:
1. Voltage regulator card (Model 39H)
2. System planar (Models 340, 34H, 350, 355, 360/36T, 365, 370/37T,
375, 380, 390, and 397 if the rear fan is failing)
3. Power supply
If the symptom did not change and all the FRUs have been exchanged go
to Step 5.
Exchange the defective fan. Go to "Map 0410: Repair Checkout" in the
Diagnostic Information For Micro Channel Bus Systems .
Maintenance Analysis Procedures (MAPs)
2-1520-3