[Help] Monitor turns on and then blacks out

Hey guys, I have a family member that their display turns on (varies from a few seconds to minutes) and then blacks out.

They have a HP Pavilion P7-1126S, which has an AMD A8 and ATI HD 6550
Full specs here

We have ruled out the monitor by trying another monitor and it does the same thing. Also have tried putting in a dedicated graphics card to test since it was using the onboard and it still has this same problem. We tried different cables and also updated graphics drivers. The problem continues and happens whether we are in bios or windows does not matter.

At this point I am thinking it could be a problem in the motherboard. Does anyone have any other suggestions?