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Light path diagnostics
Light path diagnostics is a system of LEDs on various external and internal
components of the server. When an error occurs, LEDs are lit throughout the
server. By viewing the LEDs in a particular order, you can often identify the source
of the error.
The server is designed so that LEDs remain lit when the server is connected to an
ac power source but is not turned on, provided that the power supply is operating
correctly. This feature helps you to isolate the problem when the operating system
is shut down.
Any PCI-X, memory, microprocessor, and VRM LED can be lit again without ac
power after you remove the microprocessor tray so that you can isolate a problem.
After ac power has been removed from the server, power remains available to
these LEDs for up to 24 hours.
To view the PCI-X, memory, microprocessor, and VRM LEDs, press and hold the
light-path-diagnostics button on the PCI-X board, memory card, or microprocessor
board for 30 seconds to light the error LEDs.
The LEDs that were lit while the server was running will be lit again while the button
is pressed.
Many errors are first indicated by a lit information LED or system-error LED on the
operator information panel on the front of the server. If one or both of these LEDs
are lit, one or more LEDs elsewhere in the server might also be lit and can direct
you to the source of the error.
Before working inside the server to view light path diagnostics LEDs, read the
safety information that begins on page v and "Handling static-sensitive devices" on
page 8.
If an error occurs, view the light path diagnostics LEDs in the following order:
1. Check the operator information panel on the front of the server.
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IBM ERserver xSeries 460 Type 8872 and xSeries MXE 460 Type 8874: Installation Guide
v If the information LED is lit, it indicates that information about a suboptimal
condition in the server is available in the BMC log or in the system-error log.
Important: If the server has a baseboard management controller, clear the
BMC log and system-event log after you resolve all conditions. This will turn
off the information LED and LOG LED, if all conditions are resolved.
v If the system-error LED is lit, it indicates that an error has occurred; go to
step 2 on page 75.
The following illustration shows the operator information panel.
Power-control button
USB connector
Power-on LED
Hard disk drive activity LED
Locator LED
Information LED
Release latch
System-error LED
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