IBM 7940, Problem Determination And Service Manual

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System board error LEDs and the light path button
The system-error LED on the front panel (“Front view” on page 5) is lit to indicate
that a system error has occurred. The system board has error LEDs for
microprocessors, fans, and memory that will help to locate the source of the error.
Run the diagnostic programs (“Running the diagnostic programs” on page 101) to
find the cause of the error.
When the system board error LEDs are lit to indicate an error, they remain lit when
the server is turned off, provided that the server is still connected to power and the
power supply is operating correctly.
Before you work inside the server to view error LEDs, read the safety information
that begins on page vii and “Handling static-sensitive devices” on page 30.
Remove the server cover and look inside the server for lit LEDs (“Removing the
cover” on page 31). If the server is not connected to ac power, press the light path
button. A lit LED on or beside a component identifies the component that is causing
the error.
The following illustration shows the LEDs on the system board.
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IBM System x3455 Type 7940 and 7941: Problem Determination and Service Guide