Atari 1200XL ClearPic Version
128.3 5/31/2002 by Bob Woolley
I have been fooling around with the video on the 1200XL since I first hooked
one up to a
monitor oh so long ago. The first version of ClearPic was OK, but it did
not have a composite output, just separate Chroma. As time went by I conceded
that not having composite was too limiting, no matter how much better the
video was as Luma/Chroma - particularly in the face of limited availability
for separate Chroma capable monitors. (now, of course, there are a large
number of s-video TV/monitors that look fantastic)
So, here is a pretty good upgrade for your 1200XL that looks really, really
good on a s-video TV and has a decent composite output. And, it is fairly easy
to do. I realize that other upgrades are available which really maximize the
signal bandwidth but, some of the video is better not seen, I think. This
version is designed to provide the best looking display, not the correctly
engineered circuit.
By the way, if you want to hook up a stock Atari to a s-video TV or monitor,
the Atari circuits are designed to be terminated with 75 ohm resistors. The
old fashioned monitors had the option of using 75 ohm termination, but modern
TVs do not. The result is an over-driven signal to the TV, which looks bad.
So, if you want to hook an 800, for example, to a nice s-video TV, add 75 ohm
resistors as terminators somewhere in the cable. Then it looks pretty good.
You do not need this on ClearPic.
These instructions are presented as a list of components on the 1200XL board.
For each listed part, remove the old device and add whatever is specified in
its place. Those locations shown with a - are to be left empty. I have
included a picture of a 1200XL board with all the listed components removed.
The holes are then backlit to help you locate the components. Do a nice clean
job and good luck.
Hope you like it.
