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ClearPic 2002 for your 1200XL

Preface:
Here is a new video mod, hot off the press for 2002! A new and improved ClearPic mod from Bob Woolley that corrects and enhances the video performance of the 1200XL even more than the original ClearPic. This may be the cleanest 1200XL video mod ever in both implementation and performance. RAID data recovery was not needed to enhance the video performance. I have completed the Supervideo mod in the past and was very pleased with the results, except for the slightly "over-boosted" color saturation. ClearPic 2002, on the other hand, is crystal clear and yields the cleanest, sharpest picture yet seen on the 1200XL (I am currently working on some still screen video captures to compare the output of SuperVideo to ClearPic 2002). To top it off, the mod has been simplified and requires only 10 resistors and 2 capacitors. What are you waiting for?
--the Webmaster


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.


(click to enlarge)
   
ComponentReplace With
R63 1 ohm
L15 1 ohm
C115 1 ohm
CR19 -
R22 -
C60 -
R25 75 ohms
R28 75 ohms
R23 130 ohms
R24 130 ohms
C118 -
C119 -
Q8 -
C62 68 pf
R31 1 ohm
R38 1000 ohms
R27 -
C63 1000 pf
R44 47 ohms

Add a wire from the junction of R27 and C61 to J2-5 (the empty pin on the video DIN connector)


html-ized by Dan Vernon -- May 2002