[Coco] TRS-80 Tandy Color Computer CoCo 3 RGB Video Cable

[Gene Heskett]

On Sunday 22 July 2007, Derek wrote:
>There was recently an e-bay auction (which I lost btw..grrr) for a cable
> that went from a Coco III  to a 9 pin RGB monitor. I was wondering if there
> are any schematic or instructions on how to build one of these around that
> someone would be willing to share? I see the old 9 PIN color monitors all
> the time at local thrift stores for around $5 so this would be an
> affordable way to upgrade to a nice video display. Also I ould think there
> would only be certain monitors that this cable would work with. What
> specifications would one need to look for on the monitor end?
>
>The auction which has ended is here :
> http://cgi.ebay.com/ws/eBayISAPI.dll?ViewItem&ih=009&sspagename=STRK%3AMEDW
>%3AIT&viewitem=&item=190132725303&rd=1&rd=1
>
Derek, those monitors usable with the coco's nearly ntsc video output are few 
and far between today as the few NEC 3fg's & multisync's, in addition to the 
magnavox 8cm515 and 1cm135's, and of course the shacks very cheaply made 
cm-8, have all long since either blown their high voltage circuitry or their 
crt's have faded away into the sunset.

A broadcast tv monitor is generally available yet, but at stratospheric prices 
(probably over $700 for a crt type, more for modern lcd stuff) because of the 
low production level required to fill that market.

Most (99.9% or more) of the 9 pin monitors are 31 khz vga, not 15.75 khz ntsc, 
and any attempt to slow the h-sweep of a vga designed monitor down enough to 
work with ntsc will let the smoke out of its horizontal and high voltage 
circuits in milliseconds.  Litterally.

Your best bet today is a scan doubler adapter such as Roy Justice has been 
making for us for the last year or so, and which plugs directly into the 10 
pin on the bottom of the coco3 and drives a vga (31khz hscan rate) monitor, 
one of those "5 dollar" models quite nicely, although you may find it has a 
dead color gun at that price range.  And its probably not any more expensive 
than some of the ebay auctions might fetch for an original cable.  And it has 
the added plus of being a known to work solution, I have one.

Roy, speak up, here's a customer!

>Thank you
>
>Derek
>
>
>
>
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-- 
Cheers, Gene
"There are four boxes to be used in defense of liberty:
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I'm thinking about DIGITAL READ-OUT systems and computer-generated
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