🚀 go-pugleaf

Stephen H. Fischer wrote:
> Hi,
> 
> Most of us are aware of the disappointing CoCo displays on a TV.
> 
> When the CoCo 3 was introduced the display choices were expanded to
> include an Video output and a RGB output.
> 
> Tandy produced the CM-8 monitor for the CoCo 3 RGB output.
> The large dot pitch chosen was barely able at best to produce a readable 80
> column display, but more realistically described as not quite.
> 
> Marty Goodman's advice was to buy a Sony KV-1311CR,
> a TV with Video and RGB inputs. This has remained the best
> CoCo 3 monitor and what other CoCo 3 displays are judged against.
> 
> ---------------------------------------------------------------------------
> 
> While I was working on a absurd project to display ATSC HDTV from my HTPC
> on my NTSC RCA TV I realized that the same solution could be used with the
> CoCo 3.
> 
> Some newer TV's have a S-Video input which bypasses the TV circuits used
> with Video input which degrade the picture immensely.
> 
> The "MyHD" HDTV PCI card in my HTPC can produce a 480i(720x480 interlaced,
> 15.75kHz) RGB (VGA) output.
> 
> This is not a S-Video signal but can be converted by a chip produced by
> Analog Devices.
> 
> The CoCo 3 produces a similar RGB output.
> 
> The CoCo 3 S-Video display on my TV is as good as the display on the Sony
> KV-1311CR.
> 
> As the screen is larger many persons (Gamers) will prefer the larger TV
> S-Video displays.
> 
> ---------------------------------------------------------------------------
> 
> Analog Devices has a "AD72x" series of chips that I expect all will do an
> excellent job of converting the CoCo 3's RGB output to S-Video.
> 
> I used the AD723 for my project.
> 
> AD720
> 
> AD721
> 
> AD722
> 
> AD723 $4.12 (#100)
> 
> http://www.analog.com/en/prod/0,2877,AD723,00.html
> http://www.analog.com/UploadedFiles/Data_Sheets/774020909AD725_0.pdf
> 
> AD723 Evaluation Board $75.00
>  The links on www.analog.com for the Evaluation
>  Board are circular and all lead to the basic AD723 pdf.
>  This is true for pages found in the time machine archive
>  and also for 3rd party repositories of data sheets.
>  Hopeful a copy is included with the evaluation board.
>  The original owner of my AD723 evaluation board cannot find a copy.
> 
> AD724 $6.26 (#100)
> 
> http://www.analog.com/en/prod/0,2877,AD724,00.html
> http://www.analog.com/UploadedFiles/Data_Sheets/40671345AD724_b.pdf
> 
> AD724 Evaluation Board $125.00
> http://www.analog.com/UploadedFiles/Evaluation_Boards/Tools/452661188AD724eb.pdf 
> 
> 
> AD725 $5.31 (#100)
> 
> http://www.analog.com/en/prod/0,2877,AD725,00.html
> http://www.analog.com/UploadedFiles/Data_Sheets/774020909AD725_0.pdf
> 
> AD725 Evaluation Board $245.00
> http://www.analog.com/UploadedFiles/Evaluation_Boards/Tools/120333814AD725eb.pdf 
> 
> 
> The Evaluation Boards are assembled with cables. All that you need to 
> add is
> a CoCo 3 RGB cable with a DB15 VGA connector and a connection to a 3-5 volt
> power supply. Three ~100 ohm resisters need be inserted in the R, G and B
> lines.
> 
> -------------------------------------------------------------
> 
> For the CoCo 3 I recommend that a AD724 be used. This chip has 16 leads
> instead of the 28 on the AD723.
> 
> Fewer pins mean fewer problems
> 
> There is a site with a single sided PCB that is a good starting point.
> Changes need to be made, NTSC instead of PAL and S-Video output.
> 
> Coelho's Site - VGATV Hardware Page [AD724 by Ludovico Caledon]
> http://pwp.netcabo.pt/pscoelho/vgatv/ludovico/LC-AD724.html
> 
> Drawn using Eagle 4 for Linux.
> 
> -------------------------------------------------------------
> 
> All the AD72x chips need the same external parts.
> 
> I expect that an evaluation board is really not needed in the 
> development of
> a board for the CoCo 3. There are just not too many things that can go 
> wrong
> and no adjustments are needed.
> 
> -------------------------------------------------------------
> 
> My CoCo 3 plans: To answer questions and offer advise.
> 
> As I have the Sony KV-1311CR for use with the CoCo 3 and an additional
> computer monitor that could be used, I have no real need for
> continuing with this project.
> 
> Now for the non-believers.
> 
> I have taken some digital photos of several CoCo 3 generated screens.
> 
> Taking digital photos off a TV screen has problems that are not visible to
> an human eye looking at the screen.
> 
> The raster lines appear to be too prominent. In normal viewing you will 
> want
> to be farther from the TV due to its larger size.
> 
> There is interference that shows up on some of the photos. Again I say that
> a human looking at the screen will not observe this.
> 
> I suggest that you download the Index first
> 
> "IndexSV.jpg" 204,464 Bytes
> 
> and then
> 
> "P0001814.jpg" 447,272 Bytes.
> 
> This is the CoCo 3 64 colors all on one screen display.
> 
> These photos are ones that you download and look at for 30 seconds once and
> never look at them again.
> 
> So please be kind to Dennis and not abuse his bandwidth.
> 
> ftp://maltedmedia.com/coco/CC3/Monitors/Svideo/
> 
> -----------------------------------------------------------------
> 
> Can I expect the same great display on my S-Video TV?
> 
> Yes, TV's with S-Video inputs tend to be larger, better designed and better
> built.
> 
> How much does a S-Video TV cost?
> 
> Will you believe Cheap or FREE!
> 
> We in the USA are in the process of turning off the analog NTSC TV 
> broadcast
> transmitters and having only digital ATSC OTA transmitters.
> 
> This will make a huge number of old TVs need to be replaced with HDTV sets.
> In Silicon Valley all the Analog stations now are also transmitting digital
> signals with very few exceptions. Even the Praying, Shopping and Spanish
> stations.
> 
> So when a friend says that they are going to get a new HDTV, talk to them
> about their old set. Do not wait. Those persons that have purchased TV's
> with S-Video inputs are the ones that will or already have purchased a new
> HDTV.
> 
> -----------------------------------------------------------------
> 
> The "CoCoList for Color Computer Enthusiasts " is a lively list of CoCo'ers
> that have many projects ongoing and can answer just about any question
> about CoCo's.
> 
> If you are not a member and wish to join us, download the file
> "JoinCoCo.txt" from the S-Video folder with the pictures listed
> above.
> 

Nice! I still like my Magnavox 8CM873 over the TV S-video images :)
By the way, P0001814 is a display of colors grouped for CMP as seen on 
an RGB monitor; not very useful. Makes much more sense to modify the 
program to group the colors in RGB order. You can modify your program or 
get my version of it from my web site.
http://home.att.net/~robert.gault/Coco/Downloads/Downloads.htm

The organization of RGB colors is more complex but still in four 
columns. The color numbers are no longer in sequence 0-64 but grouped by 
color subsets. It is not too hard to see how the RGB cube has been 
squashed into a square.