Heres the fix:
This requires access to the cpu and heatsink, remove the keyboard and palmrest to access the motherboard, I think you have to remove the screen too. Remove the heatsink and cpu. Reseat the cpu, heres the kicker, press firmly on the center of the cpu while turning the locking screw. Pressing the cpu hard, allows the locking mechinism to get a good bite. Turn the locking screw hard into the end of the turn. Hook up the heatsink and set it back on top of the cpu. Press down on the heatsink over the cpu, fairly strong pressure.
Now test the motherboard, use just cpu, heatsink, memory, power button board and cable and external monitor, you can use your screen instead by just hooking up the cable to motherboard, leave the screen laying flat on the table. Now push the power button with one hand and the other is still applying pressure to the heatsink, no you dont need to screw it down yet. Keep reseating the cpu with varying degrees of pressure if you dont get it go the first time.
The trick will be to get it all assembled with the same results.
There seems to be a problem with the cpu seating correctly, it must come loose and the laptops
exhibit the symtoms of no video. It might even be neccessary to insert a wafer thin piece of copper or something in between the cpu and heatsink if the heatsink doesnt apply enough pressure to cpu to keep it seated deep enough to run the computer