DaveyPocket wrote:So I plugged the my Uzebox into the Pacman CRT directly with RGB and Sync. The picture is stable, but it is very dim. I have the brightness set up to where it should be for the Pacman motherboard. Is there a certain spot on the R2R ladder that I should be taking the signal from?
What is the expected voltage & input inpedance for these monitors? Are you taking the signals before or after the 100nf capacitors?
As some of you may remember, much of the time I'm designing JAMMA arcade game boards for a living, so feel free to ask me questions-- I probably know the answer off the top of my head.
Arcade games use video signal levels left-over from when monitors were driven directly from TTL outputs. So essentially "full brightness" is in the neighborhood of ~3-3.5V and black is generally 0.4V or under (lower is better).
What you want to do on the Uzebox is remove the pulldown resistors on the video DAC outputs (the 75 ohm resistors on the schematic) -- that should give you more or less perfect output levels for a standard resolution arcade game monitor.
(It works fine, BTW. All my original testing was on my JAMMA test rig here since that's usually what I'm dealing with.)