HP ProDesk 400 G2.5 Maintenance And Service Manual page 82

Blank screen (no video).
Cause
Monitor cable is plugged into the wrong connector.
Monitor settings in the computer are not compatible with the
monitor.
Monitor is configured to use an input that is not active.
Blank screen and the power LED flashes Red five times, once every second, followed by a two second pause, and the computer
beeps five times. (Beeps stop after fifth iteration but LEDs continue flashing.)
Cause
Pre-video memory error.
Blank screen and the power LED flashes Red six times, once every second, followed by a two second pause, and the computer
beeps six times. (Beeps stop after fifth iteration but LEDs continue flashing.)
Cause
Pre-video graphics error.
74 Chapter 6 Troubleshooting without diagnostics
Solution
Systems may have a monitor connection on both the
motherboard or an add-in card. Try moving the monitor
connection to a different connector on the back of the computer
1. In Control Panel, select Category from the View by list, then
under Appearance and Personalization, select Adjust
screen resolution.
To access Control Panel in Windows 7, click Start, and then
select Control Panel.
To access Control Panel in Windows 8, from the Start
screen, type c, and then select Control Panel from the list
of applications.
2. Expand the Resolution box, and then use the sliding control
to reset the resolution.
Use the monitor's on-screen menu controls to select the input
that is being driven by the system. Refer to the monitor's user
documentation for more information on the on-screen controls
and settings.
Solution
1. Reseat DIMMs. Power on the system.
2. Replace DIMMs one at a time to isolate the faulty module.
3. Replace third-party memory with HP memory.
4. Replace the system board.
Solution
For systems with a graphics card:
1. Reseat the graphics card (if applicable). Power on the
system.
2. Replace the graphics card (if applicable).
3. Replace the system board.
For systems with integrated graphics, replace the system board.