[Color Computer] Fw: [coco] wondering about 68k machines

RJRTTY at aol.com RJRTTY at aol.com
Sun Jul 10 00:39:03 EDT 2005

In a message dated 7/9/05 11:40:21 PM Eastern Daylight Time, 
wdg3rd at comcast.net writes:

 Is there a convenient source of directions for such a conversion?  I want to 
 modify a 9" tube to pack a CC3 into an old Compaq luggable chassis. >>

        I dont have a link or anything  but I'll tell the story from memory
as best as I can (since I'm not home right now).

       The socket for the monitors main video input connector
has a pin for each red, green and blue digital
input signal of course.    I didn't have a schematic but ,Basically,
what I did was take a continuity tester and trace the circuits these inputs
where connected to.    Eventually, they each led to one of three
potentiometers labeled as "gain" on the circuit board.    The digital
signal from the input circuit of each color were fed directly to its 
potentiometer which controlled the amount of signal reaching the
picture tube driver circuit.    This is where the digital part of the
monitor meets the analog part.    The modification consists of
cuting the incoming trace at the connection terminal of these potentiometers
and soldering a jumper wire from that terminal directly to the input connector
of the monitor to the corresponding color signal pin for that potentiometer.

All you're doing is disconnecting the potentiometers from the digital
part of the monitor and feeding the analog signal directly to the
potentiometers.    Works like a charm.  And the gain adjustment
still works.

        Not all monitors are exactly the same but an equivalent configuration
should be present in all CGA monitors.  Just find the gain pots and
bypass the digital input circuit.

hope this helps

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