[Coco] S-video Prospects...

[John Kowalski]

Hi again everybody.

I've posted up some photos of the video output of the AD724 here:
http://www.axess.com/twilight/sock/graphics/svideo2.jpg

The top/left is the normal composite video output of the U.S. CoCo3.
top/right is composite generated from RGB using the AD724.
bottom/left is Svideo generated from RGB using the AD724.
bottom/right is the normal RGB output of the U.S. CoCo3.

All were displayed on the exact same monitor for convenient 1:1:1:1
comparison, but it looks like my camera's white balance drifted a bit this
time... the slightly blue tint of the "white" bar in some of the photos is
only a figment of my camera's imagination.


At 08:31 PM 05/01/2006 -0600, Christopher Hawks wrote:
>    I would! Also a couple of photos of the board. Your parts list is a
>little different from the data sheet. How about a schematic??

Here's a photo of the board - it ain't much to look at!
http://www.axess.com/twilight/sock/graphics/ad724.jpg

I tried taking a photo of the bottom too, but the glare from the copper
around the holes makes it impossible to see anything.

Yes, it's sitting inside a Game Boy cartridge case.   The 3 RCA jacks are
composite, luma and chroma.  The 74LS86 and capacitor in the bottom/right
can be entirely ignored because it isn't actually used now.  I had only put
it there at first in case the AD724 may have required the syncs to be
inverted or combined, but it works just fine with the CoCo's syncs "as-is".

One of the capacitor pairs just above the AD724 might as well be eliminated
too as I'm only using a single power supply and there isn't much point in
having two sets of power capacitors.

The circuit is pretty much as in the data sheets except some of the
resistors have been changed (3x82 Ohm in series on the RGB lines, then 3x82
Ohm to ground on the RGB lines...)  and I had to use a larger (82 pF)
capacitor on the clock crystal to get the colorburst within acceptable NTSC
frequency.


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