[Coco] cm-8, the next generation

[KnudsenMJ at aol.com]

In a message dated 4/22/04 2:19:31 PM Eastern Daylight Time, 
kevdig at hypersurf.com writes:

>   Has anybody ever hooked a tre up to a multi-sync to see what
>  actually happens? I know that if you over drive a multi-sync, the def-
>  lection circuits start snarling and spewing "colorful metaphors". But
>  what happens if you under drive them? Vertically everything should be
>  fine since 60 is within the vertical sync range for a multi-sync.
>  Horizontally will it not sync or will you just see the left half of
>  the picture (cauz it just can't scan that slow)?

If it does try to scan that slow, but it wasn't really designed to, it will 
burn up the horizontal output section.  If it syncs to a freq exactly 2X the 
Coco's horizontal, then you may see something like half the picture.  More 
modern monitors shut themselves down if the sync freqs are out of range.

>   This becomes more interesting for an LCD monitor since there
>  is no "electron beam" to push around. What would control the lower
>  sync limits? I have an LCD monitor that can be used as a TV. So it
>  can definitely sync at 15khz.

Have you tried feeding the Coco3's composite video into that LCD, same as you 
would a VCR?  It won't have the 80-column resolution but should do for games.

Of course it would be great to get inside that LCD and tap into its RGB 
circuits, thus bypassing the composite demodulator and its bandwidth limits.
  
>   Anybody know how to make a cable to interface a tre to a VGA
>  style multi-sync?

Given the connectors' pin assignments at both ends, you can figure it out.  
Marty Goodman had cookbook solutions for every workable combination, but 
haven't seen him post lately.
  
>   FYI:  The service manual lists the horizontal resolution as 480 dots.

Interesting.  Given a 5x7 character (minimum acceptable), plus one dark dot 
for spacing, that makes 6 hor. dots per char, so the CM-8 is just barely 
capable of 80 columns.  Actually it's not terrible, but it isn't as good as a 
Magnavox, and after a Coco session everything I look at has dots superimposed on it 
:-)
 
>  P.S.:    I am thinking of going after Radio Shack over this monitor
>   dying (sp?) because of the deflection coil. It really "burns    me up".

Good luck trying to sue a company over a part that burns out after 15-20 
years of usage.  Also, the coil may have failed because a transistor shorted out 
and cooked it, and failure is to high-power transistors what divorce is to 
movie stars.
> I believe that one way to
>   discourage companies from producing crap is to beat the
>   crap out of them when they do.

Nobody's denying the CM-8 is crappy :-)  but after 20 years it's kinda late.

>   I must concede that this monitor has been used fairly
>   solidly. Should I just let it go?

Try to find another busted CM-8 and get one working out of the two.
--Mike K.