Finally, since it was all set up anyway, I tried a Mac 13" 640x480 signal (same resolution, 10% faster scan rate):
No problems on vertical sync at all (just like techknight predicted). The picture is a little shorter but could easily be adjusted with the trim that's already on the analog board. However, the checkerboard pattern has become very dark. 832x624 is even worse-- all you see is the floppy icon! I think the speed of the CRT video amplifier circuit will start to become a limitation here.
Which raises another question. Has anyone tried one of the Micron Xceed replica CRT boards that are for sale online? Not only would it be a useful eventual grayscale solution, but the amplifier might also have better bandwidth than the stock CRT board.
No problems on vertical sync at all (just like techknight predicted). The picture is a little shorter but could easily be adjusted with the trim that's already on the analog board. However, the checkerboard pattern has become very dark. 832x624 is even worse-- all you see is the floppy icon! I think the speed of the CRT video amplifier circuit will start to become a limitation here.
Which raises another question. Has anyone tried one of the Micron Xceed replica CRT boards that are for sale online? Not only would it be a useful eventual grayscale solution, but the amplifier might also have better bandwidth than the stock CRT board.