Solving Power Problems

Common causes and solutions for power problems are listed in the following table.

Table 2-2Solving Power Problems

Power supply shuts down intermittently.

Cause

Solution

 

 

Voltage selector switch on rear of computer chassis (some

Select the proper AC voltage using the selector switch.

models) not switched to correct line voltage (115V or 230V).

 

 

 

Power supply will not turn on because of internal power supply

Contact an authorized service provider to replace the power

fault.

supply.

 

 

Computer powered off automatically and the Power LED flashes Red two times, once every second, followed by a two second pause, and the computer beeps two times. (Beeps stop after fifth iteration but LEDs continue flashing.)

Cause

Solution

 

 

Processor thermal protection activated:

A fan may be blocked or not turning.

OR

The heatsink is not properly attached to the processor.

1.Ensure that the computer air vents are not blocked and the processor cooling fan is running.

2.Open hood, press power button, and see if the processor fan spins. If the processor fan is not spinning, make sure the fan's cable is plugged onto the system board header.

3.If fan is plugged in, but is not spinning, then replace the heatsink/fan assembly.

4.Contact an authorized reseller or service provider.

Power LED flashes Red four times, once every second, followed by a two second pause, and the computer beeps four times. (Beeps stop after fifth iteration but LEDs continue flashing.)

Cause

Solution

 

 

 

Power failure (power supply is overloaded).

1.

Check that the voltage selector, located on the rear of the

 

 

power supply (some models), is set to the appropriate

 

 

voltage. Proper voltage setting depends on your region.

 

2.

Open the hood and ensure the 4- or 6-wire power supply

 

 

cable is seated into the connector on the system board.

 

3.

Check if a device is causing the problem by removing ALL

 

 

attached devices (such as hard, diskette, or optical

 

 

drives, and expansion cards). Power on the system. If the

 

 

system enters the POST, then power off and replace one

 

 

device at a time and repeat this procedure until failure

 

 

occurs. Replace the device that is causing the failure.

 

 

Continue adding devices one at a time to ensure all

 

 

devices are functioning properly.

 

4.

Replace the power supply.

 

5.

Replace the system board.

 

 

The incorrect external power supply adapter is being used on

The USDT power supply adapter must be at 135W and use the

the USDT.

Smart ID technology before the system will power up. Replace

 

the power supply adapter with the HP-supplied USDT power

 

supply adapter.

 

 

 

14 Chapter 2 Troubleshooting Without Diagnostics

ENWW

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HP dc7800 tower manual 2Solving Power Problems, Power supply shuts down intermittently Cause Solution
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dc7800 tower specifications

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