NTSC dot crawl is bad
 

I have a Commodore 64 monitor, a clone, Teknika MJ22, that I'm using for my father in the kitchen. It's hooked up to the cable boxes composite out, and it has always worked and always had a great picture. One day, something changed, in a very odd way. All solid colors are basically dots, kinda like a checkerboard. But all black and white areas of a picture, are sharp, REALLY sharp. Any ideas on what's going on here? Here's a picture of what it's doing with the colors. Those colors are supposed to be solid, not dots.

http://i.imgur.com/9dBJPkt.jpg

Whatever that monitor uses to suppress dots (either a simple tuned circuit chroma trap or a comb filter) has failed. You'll need a schematic to look for it, but it should be easily identifiable.

Eidt: since the black and white areas got much sharper, I'd guess this set uses a simple trap.

I haven't find a schematic for it, but I started taking the monitor apart on the counter, and it's now black and white only.

http://i.imgur.com/ClKi9Za.jpg

Fixed! There is a switch on the back panel for switching between Separate Video, or Composite. It wasn't working right anymore. Replaced it, and now: http://i.imgur.com/sHscpah.jpg

Working good.