HP Pavilion DV6000 problems (part 59454935)

I received HP Pavilion DV6000 -series notebook, model DV6732eo to be exact. It has Nvidia GeForce 8400M GS GPU and I know 8000 -series nvidia GPUs suffered from defects, I have repaired Macbook Pro with 8600M which I am currently using.

However, unlike the MBP, I'm not sure whether or not previous owner has already tried to fix this DV. It suffers from very basic symptoms, powers on but no picture on its own screen or external. I have noticed that power button also does not work, it can only started by pressing Quickstart -button. I have noticed that if I don't install any memory, the blue led with power symbol will blink and with memory stick it stays lit, this leads me to believe there is something still working in this laptop.

I have tried to fix the GPU by heating it, just as I did with this MBP but so far no success. It might be that I don't have correct temperatures, I have IR heat sensor but it is cheap chinese one and of course cannot provide as accurate readings as IR sensor on real soldering statin would.

What frustrates me is that previous owner may already tried to fix it and possibly ruined it completedly. Do you guys have any tips what to try? I think I cannot reset bios because power button does not work, the bios battery compartment seems to be bit tricky.