No-Beep Symptoms; Lcd-Related Symptoms - Lenovo ThinkPad T420si Hardware Maintenance Manual

Table 4. Beep symptoms (continued)
Symptom or error
Two or more beeps, or a continuous beep. Operating
system starts successfully.
Three short beeps, pause, three more short beeps, and
one short beep.
One short beep, pause, three short beeps, pause, three
more short beeps, and one short beep.
Only the cursor appears.
Four cycles of four short beeps and a blank screen.
Five short beeps and a blank screen.

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.

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.
FRU or action, in sequence
If a mini-PCI Ethernet card is installed, confirm that Alert
On LAN 2 in ThinkPad Setup is disabled.
1. DIMM.
2. System board
Reinstall the operating system.
System board (security chip)
System board
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.
FRU or action, in sequence
System board.
1. Reseat the LCD connectors.
2. LCD assembly.
3. System board.
Chapter 4
.
Related service information
55