Thanks for posting this. I was wondering why the image was so dull on my Xbox 360 on my Makvisions.I have one of those Makvision monitors. The switch on the remote board is to go between consumer RGB (like your dreamcast or vga arcade PCBs) and higher voltage ttl CGA/EGA pcbs.
If you are getting a dull image from consumer sources like a console, first try flicking the switch (with the monitor off). It's labeled backwards on mine. If it's still dull, it's an issue with the rgb cable. Some of the cheaper or semi diy console rgb cables over-do it with the resistors.
Try sending it a 480p signal direct from a PC gpu with a regular vga cable and you'll see it's noticeably brighter. just don't expect your Windows desktop to look good in 480p on that monitor. 480p games will look good though. I had the same issue with my PS2 tri-sync cable from Ultimarc. It's easily solved with a cheap VGA booster (also from Ultimarc).
They sell them to boost their arcade vga card signal for CGA arcade monitors. It works for this too though.
Do you happen to know how to degauss the Makvisions without a test/service/degauss or JAMMA loom hooked up to it?