IBM ThinkPad X21 2660, Hardware Maintenance Manual

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the number of missing, discolored, or lighted dots in any
background is:
SVGA: 5 or more bright dots, 5 or more dark dots, or
a total of 9 or more bright and dark dots.
XGA: 8 or more bright dots, 8 or more dark dots, or a
total of 9 or more bright and dark dots.
Symptom or error FRU or action, in
sequence
No beep, power-on indicator
on, and a blank LCD during
POST 1. System board.
LCD backlight not
working
LCD too dark
LCD brightness cannot
be adjusted
LCD contrast cannot
be adjusted
1. Reseat the LCD con-
nectors.
2. LCD assembly.
3. System board.
LCD screen unread-
able
Characters missing
pixels
Screen abnormal
Wrong color displayed
1. See important note
for "LCD-related
symptoms".
2. Reseat all LCD con-
nectors.
3. LCD assembly.
Horizontal or vertical
lines displayed on LCD 1. LCD assembly.
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 soft-
ware 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 inop-
erative. 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 com-
puter.
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ThinkPad X21