4 beeps and display normally

[amineamine]

Hello, i have a issue in my desk top hp z440.

when i wanna turn it on he start with 4 beeps , after that , i press again the power button, and he start working normally. sometimes, it takes more than 2 press on the power button to work. always the same problem. 

in short: press the button, 4 beeps, press the button again... till he work

[BeemerBiker]

From page 101 of z440 manual

Since it is intermittent problem you might try blowing dust out of power supply 

Do you have the 500 or the 700 watt supply?

If 500, have you upgraded the system to where the 500 might not be big enough?