HP DC7800 - Manual (Page 227)

Activity Beeps Possible Cause Recommended Action
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.
Table C-2 Diagnostic Front Panel LEDs and Audible Codes (continued)
Interpreting POST Diagnostic Front Panel LEDs and Audible Codes 215