My friend gave me a Dual Processor 1.8GH/z G5 A1047 a few days ago because it was broken. I thought it was a Logic Board Failure as I have heard of this. It would display apple logo and lock up. After doing the oven/heat gun reflow (I have experience with this) the machine does the same thing. I tried running on 1 CPU...
CPU A=Top
CPU B=Bottom
...and it will not start at all on CPU B, will turn on from A. After doing this, I will not get a video signal and the USB does not initialize, also no startup chime. RAM reseating and replacing does not help, PMU Reset does not help, GPU reseat/replace does not help, Battery replacement/removal does not help, I have tried everything and I am at a loss.
Also, when replacing the Logic Board, I forgot to replace the plastic shields for the back heatsink and CPUs, I also dropped the GPU screw into the PSU so I am wondering if maybe a short occurred and that is causing this.