Question My Dell pc Has the motherboard light but when it try turn the pc on the light goes away and everything cuts off

[lauchlang673]

So i haven’t used the pc in a while and im away it’s a old pc tell optiplex 390 but wondering if anyone can help me as i know nothing about pcs the motherboard light is on when plugged in but when i try turn it on it makes a noise the light goes away and the pc cuts off and if i try press the button again nothing happens

 

[Lutfij]

Welcome to the forums, newcomer!

Are you referring to the diagnostic LED's on the prebuilt? Turn to page 69;

https://dl.dell.com/manuals/all-products/esuprt_desktop/esuprt_optiplex_desktop/optiplex-390_owner's%20manual2_en-us.pdf

for the prebuilt's manual and then see what the pattern's for the LED's are and the beeps you're hearing.

 

[punkncat]

Given the age of that unit, I would take a close look at the motherboard for swelled or leaking capacitors. I would also test the power supply.