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such as: cosmic radiation, electrostatic discharge, or
software errors. FRU replacement should be considered
only when a recurring problem exists.
When analyzing an intermittent problem, do the following:
1. Run the diagnostic test for the system board in loop
mode at least 10 times.
2. If no error is detected, do not replace any FRUs.
3. If any error is detected, replace the FRU shown by the
FRU code. Re-run the test to verify that no more errors
exist.
Undetermined problems
If the diagnostic tests did not identify which adapter or
device failed, which installed devices are incorrect, whether
or not a short circuit is suspected, or if the system is
inoperative. Follow these procedures to isolate the failing
FRU (do not isolate FRUs that have no defects).
Verify that all attached devices are supported by the
computer.
Verify that the power supply being used at the time of the
failure is operating correctly. (See “Power system
checkout” on page 35)
1. Power off the computer.
2. Visually check each FRU for damage. Replace any
damaged FRU.
3. Remove or disconnect all of the following devices:
a. Non-IBM devices
b. Devices attached to the port replicator
c. Printer, mouse, and other external devices
d. Battery pack
e. Hard disk drive
f. External diskette drive
g. DIMM
h. CD-ROM and diskette drive in the UltraBase X2
i. PC Cards
4. Power on the computer.
5. Determine whether the problem has changed.
6. If the problem does not recur, reconnect the removed
devices one at a time until you find the failing FRU.
7. If the problem remains, replace the following FRUs one
at a time (do not replace a non-defective FRU):
a. System board
b. LCD assembly
Chapter 3. ThinkPad X20, X21, X22, X23, X24
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