Lenovo T420i manual Beep symptoms, No-beep symptoms, LCD-related symptoms

Beep symptoms

Table 4. Beep symptoms

Symptom or error	FRU or action, in sequence
One beep and a blank, unreadable, or flashing LCD.	1.	Reseat the LCD connector.
	2.	LCD assembly.
	3.	External CRT.
	4.	System board.
One long and two short beeps, and a blank or unreadable	1.	System board.
LCD.	2.	LCD assembly.
	3.	DIMM.
Two short beeps with error codes.	POST error. See “Numeric error codes” on page 43.
Two short beeps and a blank screen.	1.	System board.
	2.	DIMM.
Two or more beeps, or a continuous beep. Operating	If a mini-PCI Ethernet card is installed, confirm that Alert
system starts successfully.	On LAN 2 in the ThinkPad Setup program is disabled.
Three short beeps, pause, three more short beeps, and	1.	DIMM.
one short beep.	2.	System board.
One short beep, pause, three short beeps, pause, three
more short beeps, and one short beep.
Only the cursor appears.	Reinstall the operating system.
Four cycles of four short beeps and a blank screen.	System board (security chip)
Five short beeps and a blank screen.	System board

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	1.	Make sure that every connector is connected
POST.		tightly and correctly.
	2.	DIMM.
	3.	System board.
No beep, power-on indicator on, and LCD blank during	1.	Reseat DIMM.
POST.	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.

46ThinkPad T420 and T420i Hardware Maintenance Manual