Computer Screen Is Blank And External Monitor Displays Information - Compaq Armada 7800 Reference Manual

Computer screen is blank and external monitor
displays information
Possible Cause
Display was switched to the external monitor.
Solution
Press Fn+F4 to display information on the computer screen; press
Fn+F4 again to display information simultaneously on both
screens.
Possible Cause
Display switch is stuck.
Solution
Tap the switch.
16-30 Troubleshooting