HP Z4 G4 Maintenance And Service Manual page 51

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 verify the
power supply functionality.
a. Disconnect the power cord from the computer.
b. Disconnect all power supply cables from the system
board.
c. Reconnect the power cord to the power supply.
○ If the power supply fan is spinning AND the BIST
light illuminates, the power supply is good.
Consider replacing the system board.
○ If the power supply fan is not spinning OR the
BIST light does not illuminate, replace the power
supply.
Solving general problems 43