HP EliteDesk 800 G1 Tower Service Manual page 224

"No Connection, Check Signal Cable" displays on screen.
Cause
Monitor video cable is disconnected.
"Out of Range" displays on screen.
Cause
Video resolution and refresh rate are set higher than what the
monitor supports.
212 Chapter 9 Troubleshooting without diagnostics
Solution
Connect the video cable between the monitor and computer.
CAUTION: Ensure that the computer power is off while
connecting the video cable.
Solution
Restart the computer and enter Safe Mode. Change the
settings to a supported setting then restart the computer so that
the new settings take effect.
To enter Safe Mode in Windows 7:
1.
Restart the computer.
2. Press and hold the F8 key as your computer restarts,
before the Windows logo appears. If the Windows logo
appears, you must restart the computer and try again.
3.
On the Advanced Boot Options screen, use the arrow
keys to highlight the safe mode option you want, and
then press Enter.
4. Log on to your computer with a user account that has
administrator rights.
When your computer is in safe mode, Safe Mode
displays in the corners of your monitor. To exit safe
mode, restart your computer and let Windows start
normally.
To enter Safe Mode in Windows 8:
1.
Press the Windows logo
2. Select Change PC Settings, select General, and then
under Advanced startup, click Restart now.
3. Select Troubleshoot, select Advanced options,
select Startup Settings, and then click Restart.
4. Use the function keys or number keys to select the safe
mode option you want.
When your computer is in safe mode, Safe Mode
displays in the corners of your monitor. To exit safe
mode, restart your computer and let Windows start
normally.
+ l to open the Settings charm.