HP ProDesk 400 G2.5 Maintenance And Service Manual page 113

Activity Beeps Possible cause
Interpreting POST diagnostic front panel LEDs and audible codes 105
Recommended action
OR
Press and hold the power button for less than 4
seconds. If the hard drive LED does not turn on white
then:
1. Check that the unit is plugged into a working
AC outlet.
2. Open hood and check that the power button
harness is properly connected to the system
board.
3. Check that both power supply cables are
properly connected to the system board.
4. Check to see if the 5V_aux light on the system
board is turned on. If it is turned on, then
replace the power button harness. If the
problem persists, replace the system board.
5. If the 5V_aux light on the system board is not
turned on, remove the expansion cards one at
a time until the 5V_aux light on the system
board turns on. It the problem persists, replace
the power supply.