Acer Aspire 7420 Service Guide

Chapter 411 3
3Ch Advanced configuration of chipset 
registers
3Dh Load alternate registers with CMOS 
values
42h Initialize interrupt vectors
45h POST device initialization
46h 2-1-2-3 Check ROM copyright notice
48h Check video configuration against CMOS
49h Initialize PCI bus and devices
4Ah Initialize all video adapters in system
4Bh QuietBoot start (optional)
4Ch Shadow video BIOS ROM
4Eh Display BIOS copyright notice
50h Display CPU type and speed
51h Initialize EISA board
52h Test keyboard
54h Set...

11 4Chapter 4
82h Detect and install external RS232 ports
83h Configure non-MCD IDE controllers
84h Detect and install external parallel ports
85h Initialize PC-compatible PnP ISA devices
86h Re-initialize onboard I/O ports
87h Configure Motherboard Configurable 
Devices (optional)
88h Initialize BIOS Area
89h Enable Non-Maskable Interrupts (NMIs)
8Ah Initialize Extended BIOS Data Area
8Bh Test and initialize PS/2 mouse
8Ch Initialize floppy controller
8Fh Determine number of ATA drives 
(optional)
90h...

Chapter 411 5
B9h Prepare Boot
BAh Initialize DMI parameters
BBh Initialize PnP Option ROMs
BCh Clear parity checkers
BDh Display MultiBoot menu
BEh Clear screen (optional)
BFh Check virus and backup reminders
C0h Try to boot with INT 19
C1h Initialize POST Error Manager (PEM)
C2h Initialize error logging
C3h Initialize error display function
C4h Initialize system error handler
C5h PnPnd dual CMOS (optional)
C6h Initialize notebook docking (optional)
C7h Initialize notebook docking late
C8h Force check...

11 6Chapter 4
F5h Boot to Mini DOS
F6h Clear Huge Segment
F7h Boot to Full DOS
CodeBeeps 

Chapter 411 7
Index of Symptom-to-FRU Error Message
LCD-Related Symptoms
Symptom / ErrorAction in Sequence
LCD backlight doesnt work
LCD is too dark
LCD brightness cannot be adjusted
LCD contrast cannot be adjustedEnter BIOS Utility to execute “Load Setup Default Settings”, 
then reboot system.
Reconnect the LCD connectors.
Keyboard (if contrast and brightness function key doesnt 
work).
LCD inverter ID
LCD cable
LCD inverter
LCD
System board
Unreadable LCD screen 
Missing pels in characters
Abnormal...

11 8Chapter 4
The system doesn’t power-off. Power source (battery pack and power adapter). See “Power 
System Check” on page 105. 
Hold and press the power switch for more than 4 seconds.  
System board
Battery can’t be charged See “Check the Battery Pack” on page 107. 
Battery pack
System board
PCMCIA-Related Symptoms
Symptom / ErrorAction in Sequence
System cannot detect the PC Card 
(PCMCIA) PCMCIA slot assembly
System board
PCMCIA slot pin is damaged. PCMCIA slot assembly
Memory-Related Symptoms...

Chapter 411 9
The system doesnt resume from 
hibernation mode.See “Save to Disk (S4)” on page 39.
Hard disk connection board
Hard disk drive
System board
The system doesnt resume from standby 
mode after opening the LCD.See “Save to Disk (S4)” on page 39.
LCD cover switch
System board
Battery fuel gauge in Windows doesn’t go 
higher than 90%. Remove battery pack and let it cool for 2 hours.
Refresh battery (continue use battery until power off, then 
charge battery).
Battery pack
System board
System...

120Chapter 4
NOTE: If you cannot find a symptom or an error in this list and the problem remains, see “Undetermined 
Problems” on page 122. Touchpad does not work. Reconnect touchpad cable.
Touchpad board
System board
Modem-Related Symptoms
Symptom / ErrorAction in Sequence
Internal modem does not work correctly. Modem phone port
modem combo board
System board Keyboard/Touchpad-Related Symptoms
Symptom / ErrorAction in Sequence 

Chapter 4121
Intermittent Problems
Intermittent system hang problems can be caused by a variety of reasons 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 recurring problem exists.
When analyzing an intermittent problem, do the following:
1.Run the advanced diagnostic test for the system board in loop mode at least 10 times.
2.If no error is detected, do not replace any FRU.
3.If any...

122Chapter 4
Undetermined Problems
The diagnostic problems does not identify which adapter or device failed, which installed devices are incorrect, 
whether a short circuit is suspected, or whether the system is inoperative.  
Follow these procedures to isolate the failing FRU (do not isolate non-defective FRU).
NOTE: Verify that all attached devices are supported by the computer.
NOTE: Verify that the power supply being used at the time of the failure is operating correctly. (See “Power 
System Check”...