Troubleshooting a 286.. oscope level!

[tony duell]

>  might be able to get hold of the bios, but I'm worried about the 3rd

Remember the BIOS might have been specifically modified for that 
machine. Things like internal/external video selection are not going
to be in a generic desktop mchine BIOS

> EPROM. It sits in the middle of a bunch of Yamaha branded chips. The BIOS

That may well be the display character generator. In which case if it contains
_something_ you will get a display.

-tony