HP ProDesk 405 G4 Small Form Factor Maintenance And Service Manual page 85

System does not power on and the LEDs on the front of the computer are not flashing.
Cause Solution
the appropriate voltage. Proper voltage setting depends on
your region.
2. Remove the expansion cards one at a time until the 5V_aux
light on the system board turns on.
3. Replace the system board.
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 the access panel and check that the power button cable
is properly connected to the system board.
3. Check that the 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 assembly.
5. If the 5V_aux light on the system board is off, then replace
the power supply.
6. Replace the system board.
Solving general problems 75