Lenovo ThinkPad T520 Hardware Maintenance Manual - Page 55

No-beep symptoms, LCD-related symptoms, Intermittent problems, Important, Notes - backlight not working

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No-beep symptoms Table 5. No-beep symptoms Symptom or error No beep, power-on indicator on, LCD blank, and no POST. No beep, power-on indicator on, and LCD blank during POST. The power-on password prompt appears. The hard-disk password prompt appears. FRU or action, in sequence 1. Make sure that every connector is connected tightly and correctly. 2. DIMM 3. System board 1. Reseat DIMM. 2. System board A power-on password or a supervisor password is set. Type the password and press Enter. A hard-disk password is set. Type the password and press Enter. LCD-related symptoms Important: The TFT LCD for the notebook computer contains many thin-film transistors (TFTs). The presence of 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. If the LCD you are servicing has two or less visible defective pixels, it should not be considered faulty. However, if the LCD has three or more visible defective pixels, it will be deemed as defective by Lenovo and it should be replaced. Notes: • This policy applies to all ThinkPad Notebooks purchased on 1 January, 2008 or later. • Lenovo will not provide replacement if the LCD is within specification as we cannot guarantee that any replacement LCD will have zero pixel defects. • One pixel consists of R, G, B sub-pixels. Table 6. LCD-related symptoms Symptom or error No beep, power-on indicator on, and a blank LCD during POST. • LCD backlight not working • LCD too dark • LCD brightness cannot be adjusted. • LCD contrast cannot be adjusted. • LCD screen unreadable • Characters missing pixels • Screen abnormal • Wrong color displayed Horizontal or vertical lines displayed on LCD 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 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. Chapter 4. Related service information 49

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No-beep symptoms
Table 5. No-beep symptoms
Symptom or error
FRU or action, in sequence
No beep, power-on indicator on, LCD blank, and no
POST.
1.
Make sure that every connector is connected
tightly and correctly
.
2. DIMM
3. System board
No beep, power-on indicator on, and LCD blank during
POST.
1.
Reseat DIMM
.
2. System board
The power-on password prompt appears.
A power-on password or a supervisor password is set.
Type the password and press
Enter
.
The hard-disk password prompt appears.
A hard-disk password is set. Type the password and
press
Enter
.
LCD-related symptoms
Important:
The TFT LCD for the notebook computer contains many thin-film transistors (TFTs). The
presence of 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. If the LCD you are servicing has
two or less visible defective pixels, it should not be considered faulty. However, if the LCD has three or more
visible defective pixels, it will be deemed as defective by Lenovo and it should be replaced.
Notes:
•
This policy applies to all ThinkPad Notebooks purchased on 1 January, 2008 or later.
•
Lenovo will not provide replacement if the LCD is within specification as we cannot guarantee that any
replacement LCD will have zero pixel defects.
•
One pixel consists of R, G, B sub-pixels.
Table 6. LCD-related symptoms
Symptom or error
FRU or action, in sequence
No beep, power-on indicator on, and a blank LCD during
POST.
System board
•
LCD backlight not working
•
LCD too dark
•
LCD brightness cannot be adjusted.
•
LCD contrast cannot be adjusted.
1.
Reseat the LCD connectors
.
2. LCD assembly
3. System board
•
LCD screen unreadable
•
Characters missing pixels
•
Screen abnormal
•
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.
Chapter 4
.
Related service information
49