Got a 1200XL with bad video? With a few simple changes under the
hood, you can get rid of that tearing, fuzzy screen and add separate
CHROMA operation.
Unlike the movies, the sequel to the CLRPIC modification is much
"better" than the original. If you were disappointed that the CLRPIC
mod did not allow for a COMPOSITE output, or felt intimidated by the
lengthy list of changes in the original upgrade, then you are at the right
place. This version only requires you to remove 10 components and
add 4 wires and 4 components! IT IS STILL A GOOD IDEA TO HAVE
SOME ELECTRONICS SOLDERING SKILLS. Also, these changes
were developed empirically, which means I just diddled with the values
until they worked. The output is very good - better than an 800XL and,
depending on your preference for overdriven characters, better than a
130XE or 800 in separate CHROMA or COMPOSITE video.
On with the changes. As in the original CLRPIC article, I will list the
existing component in the left column and what to put in it's place in
the right column. A "--" indicates that nothing is to be connected and
"wire" calls for a jumper, shorting out the part.
REMOVE: REPLACE WITH:
C115 10uf
wire
C60 100pf
--
R187 1meg
2.2K
L15 820uh
wire
R188 750
680
CR19 1N4148
--
C119 3.9pf
--
C62 10pf
wire
R24 180
47
R23 180
47
Add a wire from R44 (either side) to pin 5 of J2.