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Intermittent problems
Intermittent system hang problems can be due to a variety
of causes that have nothing to do with a hardware defect,
such as cosmic radiation, electrostatic discharge, or
software errors. FRU replacement should be considered
only when a problem recurs.
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. Rerun the test to verify that no more errors
exist.
Undetermined problems
If the diagnostic tests did not identify the adapter or device
that has failed, if wrong devices are installed, or if the
system simply is not operating, 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 39.)
1. Turn 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-ThinkPad 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 Ultrabay
i. PC Cards
4. Turn on the computer.
5. Determine whether the problem has been solved.
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 nondefective FRU):
a. System board
b. LCD assembly
Symptom-to-FRU index
ThinkPad T40/T40p, T41/T41p, T42/T42p Series 65