Solved: Screen blacks out for a few seconds irregularly

Hello,

I try to fix my grandma's pc.

The problem is that the monitor blacks out for a few seconds now and then.

I put up a clean install from windows 7 ultimate. So all software problems are solved with this.

The motherboard has been replaced 2 months ago (Asrock FM2A55M-DGS). She uses the onboard video card.

The processor is an AMD A4-5300.

When i was testing and installing the windows updates at home, the problem occured maybe 2x in 4 hours this morning.

When i got to her house putting the computer to use (as i thought it was fixed tho), the screen blacks out again like 1x in about 10 mins, sometimes it happens multiple times in 5 minutes too.

I now think it might be the psu giving just enough/just not enough power to the motherboard, and the first thing that would shut down would sound logically as the monitor to me.

Also when the monitor is black and you are typing something, when the monitor is back, the text you typed is there. So the system itself does constantly have enough power.

Does anyone have ideas to help me out with this?

thanx in advance!

Thomas