Lenovo THINKPAD X120E Hardware Maintenance Manual page 44

d. Battery pack
e. Hard disk drive
f. External diskette drive or optical drive
g. DIMM
h. Optical disk or diskette in the internal drive
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
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ThinkPad X100e and X120e Hardware Maintenance Manual