This is how the GPU looks on board, take no notice of the smeared thermal paste, it was all cleaned off.
The underneath of the heat shield
I have now tried re flowing the GPU with a heat gun, i have done this many times before on other ps3's with success every time. However . . after adding paste and building the system back up . . .
i have the same problem. It turns on like it is going to work, YLOD's and goes back to a flashing standby light.
If i hold the power on for a display reset, after the first beep it actually turns the console off with a solid red standby light.