HP elite 8300 SFF not showing anything on screen, going off after 1 minute

[Chisala_Chibesa]

Product: QV996AV

Serial: [Personal Information Removed]

my hp elite 8300 was off for about two weeks because i was away from home for work, when i got back i tried turning it on but i it could not show anything on the screen and it goes off after about a minute. i tried searching for solutions in this community but all of them either involve a problem with the ram, the motherboard or my monitor. i have tried resitting the RAM, tried new chips, i even tried turning it on with no ram at all but it does the same thing every single time..

1. click power button

2. fans go on, motherboard light is on

3. no warning beeps or specific code light flashes

4. after one minute the desktop goes off

this happens weather the pc has ram sticks inserted or not, it also happens with brand new ones in. please what am i supposed to do to fix this? 

thanks in advance.

[itsmyname]

What happens if you disconnect the power/data cables from the disk-drive, and then start-up your computer? Does it actually "power-off" or go into "hibernate" mode?

[Chisala_Chibesa]

i just tried removing the power and data cables, that doesn't seem to make a difference unfortunately....

it had been off for two weeks straight, by the time i got back it could not go on anymore....but yes, before the two weeks it "powered off" no hibernation