Diagnostic Light Codes During Post - Dell OptiPlex 760 Service Manual

WARNING: Before working inside your computer, read the safety information that shipped with your computer. For additional safety best
practices information, see the Regulatory Compliance Homepage on www.dell.com at www.dell.com/regulatory_compliance.
To help troubleshoot a problem, your computer has four lights labeled 1, 2, 3, and 4 on the front panel.
NOTE: If you are using an ultra form factor computer, the diagnostic lights are present on the back panel. See the Setup and Quick Reference Guide that
ships with your computer for more information.
When the computer starts normally, the lights flash, and then turn off. If the computer malfunctions, use the sequence of the lights to help identify the
problem.
NOTE: After the computer completes POST, all four lights turn off before booting to the operating system.

Diagnostic Light Codes During POST

Light Pattern Problem Description
The computer is either turned off or
not receiving power.
Off
A possible motherboard failure has
occurred.
Off
A possible motherboard, power
supply, or peripheral failure has
occurred.
Blinking Amber
No CPU present.
Steady Amber
Memory modules are detected, but a
memory power failure has occurred.
Steady Amber
A possible CPU or motherboard
failure has occurred.
Suggested Resolution
Reseat the power cable in the power connector on the back of the computer and the
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electrical outlet.
Bypass power strips, power extension cables, and other power protection devices to verify
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that the computer turns on properly.
Ensure that any power strips being used are plugged into an electrical outlet and are
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turned on.
Ensure that the electrical outlet is working by testing it with another device, such as a lamp.
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Ensure that the main power cable and front panel cable are securely connected to the
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system board.
Unplug the computer. Allow a minute for the power to drain. Plug the computer into a
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working electrical outlet and press the power button.
If the problem persists, contact Dell (see
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Power off computer, leaving the computer plugged in. Press and hold the power supply test
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button on the back of the power supply unit.
If the power supply diagnostic light next to the switch illuminates, the problem may be with
your system board. Contact Dell (see
If the power supply diagnostic light 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. Contact Dell (see
If the power supply diagnostic light still does not illuminate, disconnect the power supply
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from the system board, then press and hold the power supply button.
If the light illuminates, there could be a problem with the system board.
If the power supply diagnostic light still does not illuminate, the problem is probably with the
power supply.
Contact Dell (see Contacting
Reinstall the processor and restart the system. If the computer still fails to boot, inspect the
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processor socket for damage.
If the problem persists, contact Dell (see
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If two or more memory modules are installed, remove the modules, then reinstall one
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module and restart the computer.
If the computer starts normally, continue to install additional memory modules (one at a
time) until you have identified a faulty module or reinstalled all modules without error.
If only one memory module is installed, try moving it to a different DIMM connector and
restart the computer.
If available, install verified working memory of the same type into your computer.
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If the problem persists, contact Dell (see
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Replace the processor with a known good processor. If the computer still fails to boot,
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inspect the processor socket for damage.
If the problem persists, contact Dell (see
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