HP Parvilion P6210y Will not boot

I have an HP Parvilion P6210y computer the monitor video went out, rebooted computer which stayed on for short time and will not boot now. Green light on the back of PSU will not light, tried different power cord and test all power sources. Use HP web site to problem shoot PSU ending with buying a new PSU, same name brand and wattage. With all cables plugged in and pressing the case switch the PSU green light goes out. Disconnected everything on MB and reconnected, plugged in Ram one stick at a time and tried different configuration of ram, no change. When the 24 pin power cable is disconnected from MB the PSU green light will stay on when the case switch is pressed but that is all. When the 4 pin ATX CPU power cable is unplugged and the case switched is pressed PSU come alive, case fan starts, CPU fan starts, case switch lights up and HD chatters, then all stops except PSU fan. There are no burned, popped components on the MB, everything clean and in excellent condition throughout the computer case. The house where the computer resides has had several power outages lately but no lighting strikes, I suspect that the onboard video is the issue, can any one confirm or have further problem solving ideas.