Dell OptiPlex 990 (Early 2011) - Manual (Page 70)

• Ensure that any power strips being used are plugged
into an electrical outlet and are turned on.
• Ensure that the electrical outlet is working by testing it
with another device, such as a lamp.
• Ensure that the main power cable and front panel cable
are securely connected to the system board.
LED
Power Button
Problem Description A possible system board failure has occurred.
Troubleshooting Steps Unplug the computer. Allow one minute for the power to drain.
Plug the computer into a working electrical outlet and press
the power button.
LED
Power Button
Problem
Description A possible system board, power supply, or peripheral failure has
occurred.
Troubleshooting
Steps
• Power off computer, leaving the computer plugged in.
Press and hold the power supply test button at the rear
of the power supply unit. If the LED next to the switch
illuminates, the problem may be with your system
board.
• If the LED next to the switch does not illuminate,
disconnect all internal and external peripherals, and
press and hold the power supply test button. If it
illuminates, there could be a problem with a peripheral.
• If the LED still does not illuminate, remove the PSU
connections from the system board, then press and
hold the power supply button. If it illuminates, there
could be a problem with the system board.
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