[Coco] [Color Computer] The Best Monitor for a CoCo 3 is a TV. (Really!)

Mon Jul 11 03:33:08 EDT 2005

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.

-- 
Stephen H. Fischer

Brought to you by the 6809, the 6803 and their cousins! 
Yahoo! Groups Links

<*> To visit your group on the web, go to:
    http://groups.yahoo.com/group/ColorComputer/

<*> To unsubscribe from this group, send an email to:
    ColorComputer-unsubscribe at yahoogroups.com

<*> Your use of Yahoo! Groups is subject to:
    http://docs.yahoo.com/info/terms/