Hp compaq 4 red beeps

[BemMoertz]

Hello I have a Hp compaq 8000. Ever since we got the PC it always booted up weird but it still worked. I put a graphics card in it and it ran fine for a few days. I come back a couple months later and it's all finicky, it turns on for awhile then randomly shuts off but it would run eventually. I then took the graphics card out and left the PC. But a couple months later I came back and it worked fine and I was using it for hours. I needed a second screen so I put the graphics card in and went to grab a cable but when I got back it was turned off. I tried to start it and I get 4 red beeps, so I got a new 500w smart power supply and a adapter cable and it's still giving me the 4 beeps what can I do?

[Prométhée]

hi

Red Power LED flashes four times, once every second, followed by a two second pause. Beeps stop after fifth iteration but LEDs continue until problem is solved.

Power failure (power supply is overloaded).

OR

The incorrect external power supply adapter is being used on the USDT.

1. Open the hood and ensure the 4 or 6-wire power supply cable is seated into the connector on the system board.
2. 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.
3. Replace the power supply.
4. Replace the system board.

OR

The USDT power supply adapter must be at 135W and use the Smart ID technology before the system will power up. Replace the power supply adapter with the HP-supplied USDT power supply adapter.

https://support.hp.com/sg-en/document/c01941944