[Coco] 1702 monitor

[Barry Nelson]

> Mike Delyea
> Thu May 17 22:00:44 EDT 2018
> Thanks guys.  Barry, $75?  The monitor isn't worth that much.  I was hoping
> for something I could hack together - no offense.
Sorry, but no such luck. S-video is a completely different type of signal from both composite and RGB. Not sure why you say the monitor isn’t worth that much, I don’t think they make them anymore… :) My RGB to SCART trick works because SCART has an RGB signal that is nearly identical to the CoCo 3’s output, just the connector is different. RGB to S-video is a completely different video format, although since that monitor is 15khz, at least you don’t have to scale the signal. You might be able to build something out of an AD724 chip, but if you haven’t designed a circuit before, this will be challenging to say the least. The link below has some info. You could get the RGB signals from the bottom of the CoCo 3, and cheat and connect the composite video to the sync pin like I do with my SCART solution.

http://www.cpcwiki.eu/index.php/RGB_SVideo <http://www.cpcwiki.eu/index.php/RGB_SVideo>

The AD724 is a surface mount chip as is the AD725 which is a similar chip. Here is a link to the AD725 data sheet which includes a reference schematic.

http://www.analog.com/media/en/technical-documentation/data-sheets/AD725.pdf <http://www.analog.com/media/en/technical-documentation/data-sheets/AD725.pdf>

Using either an AD724 or an AD725 and probably less than $15 in parts in theory you could build a RGB to S-video converter, as long as you are willing to add about $100 in blood, sweat, and tears. :) It actually shouldn’t be TOO bad, as circuit development goes, but will require some trial and error.

I also found this prebuilt converter for $34 + $4.45 shipping:

https://www.ebay.com/itm/RGB-to-s-video-composite-converter-adapter/183207486638?hash=item2aa80464ae:g:FkMAAOSwkOda6xUf <https://www.ebay.com/itm/RGB-to-s-video-composite-converter-adapter/183207486638?hash=item2aa80464ae:g:FkMAAOSwkOda6xUf>