Solving Scsi Problems; Solving Power Problems - IBM 7985 Problem Determination And Service Manual

Solving SCSI problems

Note: This information also applies to Serial Attached SCSI (SAS) problems.
For any SCSI error message, one or more of the following devices might be
causing the problem:
v A failing SCSI device (adapter, drive, or controller)
v An incorrect SCSI termination jumper setting
v Duplicate SCSI IDs in the same SCSI chain
v A missing or incorrectly installed SCSI terminator
v A defective SCSI terminator
v An incorrectly installed cable
v A defective cable
For any SCSI error message, follow these suggested action in the order in which
they are listed until the problem is solved.
v Make sure that SCSI devices are turned on before you turn on the server.
v Make sure that the cables for al external SCSI devices are connected correctly.
v If an external SCSI device is attached, make sure that the external SCSI
v Make sure that the last device in each SCSI chain is terminated correctly.
v Make sure that the SCSI devices are configured correctly.

Solving power problems

Power problems can be difficult to solve. For example, a short circuit can exist
anywhere on any of the power distribution buses. Usually, a short circuit will cause
the power subsystem to shut down because of an overcurrent condition. To
diagnose a power problem, use the following general procedure:
1. Turn off the server and disconnect all ac power cords.
2. Check for loose cables in the power subsystem. Also check for short circuits, for
3. If a power-channel error LED on the system board is lit, perform the following
termination is set to automatic
example, if a loose screw is causing a short circuit on a circuit board.
steps; otherwise, go to step 4. See "System-board LEDs" on page 17 for the
location of the power-channel error LEDs. Table 3 identifies the components
associated with each power channel, and the order in which to troubleshoot the
components.
a. Disconnect the cables and power cords to all internal and external devices.
Leave the power-supply cords connected.
b. Remove each component that is associated with the LED, one at time, in
the sequence indicated in Table 3, restarting the server each time, until the
cause of the overcurrent condition is identified.
Table 3. Components associated with power-channel error LEDs
Power-channel
error LED Components
A Fan 4, fan 6, fan 8, fan 9, microprocessor 1, system board (integrated
voltage regulator)
B Fan 1, fan 2, fan 3, fan 5, VRM, IDE CD/DVD cable, IDE CD/DVD
media backplane, microprocessor 2, system board
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Chapter 3. Diagnostics