Hi

I've had a Mega PC for a while now and after re arranging the games room I thought I'd break it out and have a game of afterburner. Unfortunately the MegaDrive side doesn't work and the PC side has some odd artefacts on the display. After a bit of testing if the cartridge detect switch is activated on PC mode the display artefacts go away, or if you set the jumpers so it is forced to PC mode without the Mega Drive ISA card attached the PC display is good. With the switch set to Mega Drive mode the screen sometimes shows a fuzzy image which is rolling. My guess is there is something up with switching between modes, I tested the continuity on the switch and that behaves as expected. Now I'm at a loss as what to investigate next, I looked for the technical reference manual but the only one I can find has a really poor scan it's very hard to make out the text.

Any ideas what to investigate at would be appreciated.

Cheers