Desk top Mac not turning on

Hey there,

we have an old desk top Mac and it’s refusing to turn on even after unplugging for 15 secs and holding down the power button for 10 seconds, along with holding down various other buttons at the same time, it’s as dead as a door nail! So can this be fixed by me or somebody with some skills?

Hopeful for an answer.

Thanks everyone.

Tracey