Can any of your old PCs display .bmp files?
Here are four 256 color .bmp files of the same test screens, which are each sub-100KB. If you want them in a different format, I'll make them.
https://dl.dropboxusercontent.com/u/32377930/tests.zip(The "converge" one I made myself.)
I took just a couple shots of my TV so you can see what to look for. I used an RGB modded Supergrafx and the 240p test suite.
The backlit zone test - both shots are of a single small white square against an all black background. The first one has the square in the center of the screen, while the second one has it in the top right corner. The exaggerated red and blue around the edges you see in the corner shot are a problem of convergence. Basically, the three light guns in the CRT can aim at a center pixel more uniformly than they can at a corner pixel. If I put the white square in the top left corner, the problem roughly reverses. This has nothing to do with signal quality.
Center:
(This looks much nicer when you're not zoomed in so closely)
Top right corner:
(This only happens in the very corner of the screen. If I move it an inch toward the center, the effect nearly disappears)
Next, here's the checkerboard pattern. The first pic is of the center, while the second is of the center-right side.
Center:
Center-right, from slightly further away and at a slight angle:
Again, this is mostly a matter of the light guns being able to aim at the center of the screen more accurately than the sides.
I'd actually like to take a shot of a second TV I have, because it freaks out with this pattern even in component video (it doesn't have an RGB input). It actually tints the whole thing red, and although you can make out the black and white dots, it's not very uniform across the screen.
If you try and display this with a composite signal, or even an s-video signal under less than ideal circumstances, it's a mess. If your TV itself is not so good, it's a mess. I actually have a much cheaper Sony from around the same period that also has an RGB input, and it's still pretty bad. Truly, the checkerboard pattern is the toughest one for a setup to pass.
I can take shots of the color bleed test later, but it does pretty well with those. Only the blue is a little less sharp than the others.
