Thanks for posting this! He was helping me with my Pac-Man. The monitor chassis brand is actually Visual Displays model 125, but still off-brand. I did A TON of searching on this issue today trying to determine if the problem is "hula" or "humbar". It is very similar, if not exactly like, what is found in the animation at the top of this page, but there's no hum that accompanies it:
http://www.twobits.com/Humbar/
It's a solid wave at a constant rate across the screen. The old G07 I had in it didn't have this wave, but is being replaced because the chassis was pretty scorched, the colors were bad even with some caps replaced, and the screen had a lot of burn-in. I haven't made any other adjustments to this machine since I got it. Here's a list of what I was going to try, based on thread searches for problems that sounded similar:
1. Unplug fan (we tried this last night, didn't do anything)
2. Put ground wire on monitor frame
3. Clean edge connector/fuse block, possibly replace it + fuses (I don't think this is the problem since it previously didn't have this problem
4. Adjust screen brightness/size
5. Unplug degaussing coil (we tried this too with no positive results)
6. Tie sync pin wires together (tried this--no luck)
7. Test replace power supply
8. Make sure speaker wires aren't near ground strap
9. Adjust Horizontal Hold/Frequency
I saw that many people suggested adjusting the B+ voltage, but I looked all over the chassis and didn't see anything marked as such. I will try to have a video of this problem tonight, if possible. Anything else I missed in my note-taking session?