Dell OptiPlex 755 User Manual page 204

CAUTION: Before you begin any of the procedures in this section, follow the safety instructions in the Product Information Guide.
If the power light is green and the computer is not responding —
If the power light is blinking green —
normal operation.
If the power light is off — The computer is either turned off or is not receiving power.
Reseat the power cable in the power connector on the back of the computer and the electrical outlet.
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Bypass power strips, power extension cables, and other power protection devices to verify that the computer turns on properly.
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Ensure that any power strips being used are plugged into an electrical outlet and are turned on.
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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 system board (see the "System Board Components" section for
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your computer).
Perform the power supply self-test, if applicable (see
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If the power light is blinking amber —
Ensure that the voltage selection switch is set to match the AC power at your location (if applicable).
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Ensure that all components and cables are properly installed and securely connected to the system board (see the "System Board Components"
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section for your computer).
Perform the power supply self-test, if applicable (see
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If the power light is steady amber —
Ensure that the processor power cable is securely connected to the system board power connector (POWER2) (see the "System Board Components"
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section for your computer).
Remove and then reinstall all memory modules (see Memory).
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Remove and then reinstall any expansion cards, including graphics cards (see the "Cards" section for your computer).
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Perform the power supply self-test, if applicable (see
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Eliminate interference — Some possible causes of interference are:
Power, keyboard, and mouse extension cables
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Too many devices connected to the same power strip
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Multiple power strips connected to the same electrical outlet
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Power Supply Self-Test
CAUTION: Before you begin any of the procedures in this section, follow the safety instructions in the Product Information Guide.
If your mini tower, desktop, or small form factor computer has been certified for ENERGY STAR® 4.0, then your power supply is equipped with a self-test
feature to help with troubleshooting power problems. The self-test feature can be performed with the power supply connected to computer devices or in
isolation. The test button and LED are accessible externally on the back of the power supply (where the AC plug is located).
NOTE: The power supply self-test feature is available only with ENERGY STAR 4.0 power supplies.
1 test button
2 test LED
To perform the power supply self-test:
1. Turn your computer off and disconnect the computer from the electrical outlet.
2. Disconnect the DC power supply connectors from the system board and all internal devices. The procedure for disconnecting the power supply cables
depends on the form factor of your computer:
For the mini tower, see
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See
The computer is in standby mode. Press a key on the keyboard, move the mouse, or press the power button to resume
Power Supply
The computer is receiving electrical power, but an internal power problem may exist.
Power Supply
A device may be malfunctioning or incorrectly installed.
Power Supply
Power Supply
Diagnostic Lights.
Self-Test).
Self-Test).
Self-Test).