IBM ThinkPad T20, Hardware Maintenance Manual

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Symptom-to-FRU index
LCD-related symptoms
Important
The TFT LCD for the notebook computer contains
many thin-film transistors (TFTs). A small number of
dots that are missing, discolored, or always lighted is
characteristic of TFT LCD technology, but excessive
pixel problems can cause viewing concerns. The LCD
should be replaced if the number of missing,
discolored, or lighted dots in any background is:
Ÿ
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 System board.
Ÿ
LCD backlight not
working
Ÿ
LCD too dark
Ÿ
LCD brightness cannot
be adjusted
Ÿ
LCD contrast cannot
be adjusted
1. Reseat the LCD
connectors.
2. LCD assembly.
3. System board.
Ÿ
LCD screen
unreadable
Ÿ
Characters missing
pixels
Ÿ
Screen abnormal
Ÿ
Wrong color displayed
1. See important note
for “LCD-related
symptoms.”
2. Reseat all LCD
connectors.
3. LCD assembly.
4. System board.
Horizontal or vertical lines
displayed on LCD 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
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.
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ThinkPad T20 HMM