nfg.forums

The video chip in the CV outputs component video natively..

I have tapped it with a trim pot on each of the 3 lines and cannot find settings that produce satisfactory results with all titles - for example the colours of Donkey Kong can be very accurately produced, but Burger Time and Frogger leave somthing to be desired.  Overall, I think the colours appear a bit "washed out" - this can be helped a bit by increasing the resistance on the Y line, but only a bit...

I have noticed a few dealers selling mods and modded systems, so I would suggest that as long as they are only using resistors their mods may not be optimal.

I am hoping to be able to get this one nailed, but I don't have the tools or the knowledge to take the next step...  The data sheet for the TMS9928 recommends 330 ohm resistors on each line on one page and then shows a diagram with 470ohms... I have tried both...

Has anyone had any luck with this mod that is willing to share some info?

I will post some screen shots later.

There's a PDF file from one of the commercial mod vendors that might interest you. Their mod is embodied on a separate daughter board with parts similar to what you're describing, and apparently it's one of the more succesful models:

http://www.8bitdomain.com/Colecovision%20V...bc587b47725f1d0

Note also this post from AtariAge. The consensus is that the native Colecovision component output isn't voltage-matched to NTSC inputs.

http://www.atariage.com/forums/index.php?s...0&#entry1190243

-KKC, who has way too much of this stuff bookmarked...

Here are some screen shots to illustrate what I was trying to describe:

First the good:

Donkey Kong

RF -

Component -

Donkey Kong looks great... the only loss really is in the amount of yellow on the second level.

...and what most other games look like:

Frogger

RF -

Component -

On Frogger you can see that there is no real "brown". The image also appears too bright.

dear god i can't see the whole image..  i'll have to load it in Preview to scale it...

Quotedear god i can't see the whole image..  i'll have to load it in Preview to scale it...

I have reduced them to 800x600 -  B)  

thanks

I wonder if Cr is weak..  it almost looks like red isn't as strong as it should...

Lost Monkey,

The video chip won't drive your TV directly (which acts as a 75 ohm resistor to ground). You'll need some form of active buffer circuit between the chip and your video output to set the correct voltage. A few smiple transistor circuits is all you'd need - like the board that kendrick linked to.

QuoteLost Monkey,

The video chip won't drive your TV directly (which acts as a 75 ohm resistor to ground). You'll need some form of active buffer circuit between the chip and your video output to set the correct voltage. A few smiple transistor circuits is all you'd need - like the board that kendrick linked to.

I am going to put together a buffer tonight on breadboard.