As soon as i connect the power cable to my PC hp Compaq d503,my pc start blinking red 4 time for 1 second what the problem please help

Red Power LED
flashes once
every two
seconds.
OR
Red Power LED
flashes four
times, once
every second,
followed by a
two second
pause.
None Power failure
(power supply is
overloaded).
1. Check that the voltage selector,
located on the rear of the power
supply, is set to the appropriate
voltage. Proper voltage setting
depends on your region.
2. Open the hood and ensure the 4-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 blinking should be in a pattern.

Power Green On (S0) Computer on
Power Green 1 blink every 2 seconds (S1) Suspend Mode
Power Green 1 blink every 2 seconds (S3) Suspend to RAM
Power Green Off (S4) Suspend to Disk (if applicable)
Power Clear Off (S5) Computer off
Power Red 1 blink followed by 2-second
pause - Repeat
Power Supply failure
Power Red* 2 blinks 1 second apart CPU thermal shutdown
Power Red* 3 blinks 1 second apart CPU not installed
Power Red* 4 blinks 1 second apart Power supply overload (crow bar)
Power Red* 5 blinks 1 second apart No memory
Power Red* 6 blinks 1 second apart No graphics
Power Red* 7 blinks 1 second apart System board failure (detected prior to video)
Power Red* 8 blinks 1 second apart Invalid ROM
Hard Drive Green Blinking Hard drive activity
*Blinking

How many times does the red light come on ? It should blink a number of times, then go off for a little while, and start blinking again. The number of blinks within each cycle will help you find out what is wrong:
Number of 1-second red LED blinks followed by 2-second pause, then repeats:
2-processor thermal protection activated
3-processor not installed
4-power supply failure
5-memory error
6-video error
7-PCA failure (ROM detected failure prior to video)
8-invalid ROM, bootblock recover mode
(http://h18000.www1.hp.com/products/quickspecs/productbulletin.html#spectype=worldwide&type=html&docid=11632)

A bad power supply, OR a bad motherboard. And I hate to tell you, but it's more common for the motherboard to fail first. Especially in those HP/Compaq slimline PCs.

It's because there's very little airflow, and system overheats and burns out. I've had many customers with the same issue.

The good news is you can still recover your data from the hard drive, just take the drive out, and hook it up inside another desktop with SATA connections, or get a SATA-to-USB adapter, they cost about $15

Are they Long Beeps? Does the RED led light on the front show up?
If there is no RED led light blinking, then the problem is your RAM.
If there IS a RED led Light showing up, then the problem is your Power Supply.

It all depends how many beeps there were.
From http://h18000.www1.hp.com/products/quickspecs/12253_div/12253_div.HTML
Diagnostic LED Explanation Table Number of 1-second red LED blinks followed by 2-second pause, then repeats:
2-processor thermal protection activated
3-processor not installed
4-power supply failure
5-memory error
6-video error
7-PCA failure (ROM detected failure prior to video)
8-invalid ROM, bootblock recover mode

I have only really come across 4 beeps = order new Power Supply or 5 Beeps = reseat the memory and hope it works

Regards,

Oli

ur pc needed power supply

System does not power on and the LEDs on the front of the computer are not flashing.
System unable to power on.
Press and hold the power button for less than 4 seconds. If the hard drive LED turns green, then:
1.Check that the voltage selector is set to the appropriate voltage.
2.Remove the expansion cards one at a time until the 3.3 V_aux light on the system board turns on.
3.Replace the system board.
OR
Press and hold the power button for less than 4 seconds. If the hard drive LED does not turn on green then:
1.Check that the unit is plugged into a working AC outlet.
2.Open hood and check that the power button harness is properly connected to the system board.
3.Check that both power supply cables are properly connected to the system board.
4.If the 3.3 V_aux light on the system board is on, then replace the power button harness.
5.If the 3.3 V_aux light on the system board is off, then replace the power supply.
6.Replace the system board.

Here is what is says in the owners manual in what to do in this case, Hope this is a Help, Happy Holidays
Red Power LED
flashes five times,
once every second,
followed by a two
second pause.
5 Pre-video memory
error.
1. Reseat DIMMs. Power on the
system.
2. Replace DIMMs one at a time to
isolate the faulty module.
3. Replace third-party memory with
HP memory.
4. Replace the system board.
Red Power LED
flashes six times,
once every second,
followed by a two
second pause.
6 Pre-video graphics
error.
For systems with a graphics card:
1. Reseat the graphics card. Power on
If you need anymore let me know and I will post them for you.

it all depends on the number of flashes , pause, repeat.
Since the problem did not indicate any beeps her is the following info


Power LED blinks RED 2 times, one every second, followed by a
2-second pause. = Processor Thermal Protection Activated


3 blinks 1 second apart = Processor not installed (not an indicator for a bad processor).

4 blinks 1 second apart .= Power Failure (power supply is overloaded)

Other possibilities are:
5 blinks 1 second apart No memory
6 blinks 1 second apart No graphics
7 blinks 1 second apart System board failure (detected prior to video)
8 blinks 1 second apart Invalid ROM