In theory, someone can point you can't use two power supply points in one device
Sure you can, no problem. As long as there is no potential difference. And, you won't encounter that.
Check the voltage levels on different points on the computer.
I expect if they are different enough to point out a problem, you have already burnt out some traces (or are VERY close to doing it)!
Does the Meditator 1200 have a power connector? I know the A3000D and A4000T ones do.
