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IBM ThinkPad A20m Hardware Maintenance Manual: Lcd-related Symptoms

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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:
v SVGA: 5 or more bright dots, 5 or more dark
dots, or a total of 9 or more bright and dark dots.
v XGA: 8 or more bright dots, 8 or more dark dots,
or a total of 9 or more bright and dark dots.
v SXGA+: 11 or more bright dots, 13 or more dark
dots, or a total of 16 or more bright and dark
dots.
v UXGA: 11 or more bright dots, 16 or more dark
dots, or a total of 16 or more bright and dark
dots.
Note: A bright dot is a white or colored pixel that is
always on. A dark dot is a pixel that is always
off and shows as black.
Symptom or error
No beep, power-on indicator
on, and a blank LCD during
POST.
v LCD backlight not working.
v LCD too dark.
v LCD brightness cannot be
adjusted.
v LCD contrast cannot be
adjusted.
v LCD screen unreadable.
v Characters missing pixels.
v Screen abnormal.
v Wrong color displayed.
Horizontal or vertical lines
displayed on LCD.
54
ThinkPad A20m/p, A21m/p, A22m/p
Symptom-to-FRU index
FRU or action, in sequence
System board.
1. Reseat the LCD
connectors.
2. LCD assembly.
3. System board.
1. See important note for
"LCD-related symptoms".
2. Reseat all LCD connectors.
3. LCD assembly.
4. System board.
LCD assembly.

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