HP Z4 Maintenance and Service Guide - Page 57

Solving power problems

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System does not power on and the LEDs on the front of the computer are not flashing. Cause Solution 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 power problems Common causes and solutions for power problems are listed in the following table. Power supply shuts down intermittently. Cause Power supply will not turn on because of internal power supply fault. Solution Verify the power supply functionality. 1. Disconnect the power cord from the computer. 2. Disconnect all power supply cables from the system board. 3. 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 power problems 49

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System does not power on and the LEDs on the front of the computer are not
flashing.
Cause
Solution
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 power problems
Common causes and solutions for power problems are listed in the following table.
Power supply shuts down intermittently.
Cause
Solution
Power supply will not turn on because of internal power supply
fault.
Verify the power supply functionality.
1.
Disconnect the power cord from the computer.
2.
Disconnect all power supply cables from the system board.
3.
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 power problems
49