PC just shuts off for some reason

[frozensun]

Hi friends.

Due to sickness my Dad did not turn ON his PC for probably a year.

I took the PC few days ago to my room and usually in few minutes it shuts off.

I had few min to check temp on CPU before that and the CPU was not overheating.

It is an old AMD Athlon 3600+ with 2 gigs of RAM.

I thought it's a power chord cable issue but it is not.

What I noticed is that a switch on PSU is kinda loose.

I can picture it.

I did clean all the dust few days ago.

I noticed that each time I plug/unplug smth from its USB port it switches off.

Now it is evening, I will check tommorow.

What do you suggest me to do?

I only have spare PSU to test,other parts no, maybe I could purchase used RAM but who knows...

I fliped the switch ON/OFF and could see a sparkle behind it...I guess that is not good.

[frozensun]

OK so I switched the PSU..

I turned the PC on but nothing no beep no picture.

I then plugged in the optical drive which is connected over pata cable.

I got the picture but let me see how it works with different PSU.