[Coco] Bad news, good news...

[John Kowalski]

At 12:38 PM 14/12/2005 -0500, Roger "Merch" Merchberger wrote:
>Why replace, when one could adjust? How hard would it be to replace the 
>resistors with pots? Then you could adjust the colors weights to individual 
>TVs/Monitors.
>
>>The circuit is dirt simple, just some resistors and a 3904 transistor.
>
>I don't exactly have a "big" parts bin, but I'm sure I could scrape up a 
>3904 or two... ;-)
>
>Laterz,
>Roger "Merch" Merchberger

I just replaced the resistors with values that bring it closer to NTSC
specification.  The brightness of the colors now look closer to the way they
look on an RGB display.

Keep in mind, the circuit is just to generate luma.  I can try making a
little diagram of it and posting it up here.  It should be simple enough
that even an ascii diagram may do :)

Generating chroma is more complicated.  For that you'd need a chip and/or
more complex circuit.  In my case, I just tapped the signal from the
daughter board from a PAL CoCo3.  U.S. CoCo3s don't have a chroma signal to tap.

                                         John Kowalski (Sock Master)
                                         http://www.axess.com/twilight/sock/