BIG problem with my Jupiter Ace

Hi all, I've just opened up my Jupiter Ace and I think the problem I'm having with it is far more severe than a blown CPU. It looks like while I was testing it this morning the PSU was accidentally powered up, the +12(unreg) connection made contact with the barrel of the power jack (-ve) and the PSU's -ve line made contact with one of the first five expansion bus pins on the topside of the board. The CPU was getting very hot - I've since swapped the original NEC D780C (1982 datecode) with a Sharp LH0080 Z80-A-CPU IC. The replacement is also getting hot (takes about a minute for either of them to hit 50deg C). Output output and my TV can lock onto it, but the output is total garbage, no difference if I remove the CPU and ROMs or have them installed. The garbage is always the same, too, in case it matters. The replacement CPU is known-good - it came out of a working Toshiba HX-10 MSX. How should I proceed with this repair? I've got a Fluke 25 DMM and a Tek 466 storage scope at my disposal. Also, the schematics are almost unreadable. I got them from home-micros.freeserve.co.uk. Anyone got a better copy? Thanks. -- Phil. philpem(a)dsl.pipex.com http://www.philpem.dsl.pipex.com/