820-00923 Ram replacement issue

I have this 820-00923 board that was liquid damaged around J4402 and J3300. The pin for PP5V_S0_T139 on J4402 was completely melted and the pad is gone. Surprisingly this rail does not show as short still (0.445 diode). Besides this damage, I also found a dead short to ground on L7900, which is for PP1V2_S3. I ended up having to remove all 4 of the ram chips to clear that short. This board had 8GB of Samsung ram on it, and the only donor board I have for this model, has 16GB of Micron ram. I took those 4 Micron ram chips and reballed them and put them on this board. I also made sure to switch R1330 to the R1331 position and removed R1332 from the board, so the ram config should be correct. When I turn the board on now, I get 20v and about 800ma and then it drops to around 550ma after a few seconds, but the board does not turn on. No USB activity or caps lock reaction. PPVCC_S0_CPU is 0.9v, PPVCCEDRAM_S0_CPU is 0v and PPVCCGT_S0_CPU is at 0.7v, which is weird because I thought that rail should only get power under high graphics load. Is there something else I need to do when changing ram chips on these boards that I missed?


Staff member
I can only imagine RAM chip burnt because of overvoltage.
That could also damaged CPU.

Do you get now voltage at L7700/900?