Beep Symptoms; No-Beep Symptoms; Lcd-Related Symptoms - Lenovo ThinkPad T420i Hardware Maintenance Manual

Beep symptoms

Table 4. Beep symptoms
Symptom or error
One beep and a blank, unreadable, or flashing LCD.
One long and two short beeps, and a blank or unreadable
LCD.
Two short beeps with error codes.
Two short beeps and a blank screen.
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.
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ThinkPad T420 and T420i Hardware Maintenance Manual
FRU or action, in sequence
1. Reseat the LCD connector.
2. LCD assembly.
3. External CRT.
4. System board.
1. System board.
2. LCD assembly.
3. DIMM.
POST error. See "Numeric error codes" on page 47.
1. System board.
2. DIMM.
If a mini-PCI Ethernet card is installed, confirm that Alert
On LAN 2 in the ThinkPad Setup program 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.