[Coco] Using Roy's vga adapter with other computers

Gene Heskett gene.heskett at verizon.net
Sun Oct 25 07:46:33 EDT 2009

On Sunday 25 October 2009, Aaron Wolfe wrote:
>On Sat, Oct 24, 2009 at 11:21 PM,  <RJRTTY at aol.com> wrote:
>> In a message dated 10/24/2009 10:58:29 P.M.  Eastern Daylight Time,
>> aawolfe at gmail.com writes:
>>>Hello,  i have  one of Roy's adapters and it works perfectly on my cocos.
>> I have many  other "classic" >machines and wondered if it might be
>> posible to use it with  them if i can build the right cable.  Many things
>> >seem to use similar  rgb sync etc.
>> My converter already works with the Amiga and Atari520ST.
>> All that is needed is the right cable for both....
>Any hints on where to get parts for creating the cable needed?

Keep in mind when srcing the parts, that the amiga's video connector is _not_ 
a db25, but a db23.  Also keep in mind that the agnus chip cannot drive all 5 
outputs and will shut down to protect itself if the H&V sync lines aren't 
buffered with external logic. All of the cables made back in its heyday 
actually had a cmos logic chip buried in the backshell plastic casting to not 
only buffer the synch signals but also combined them into whatever mode and 
polarity that monitor needed.  It being cd4000 family cmos stuff, wasn't all 
that happy driving a 75 ohm load, so the failure rate was a problem, I've had 
to cut it off and build a new one twice now.  And I used the 74HC nand gate 
for that, much more robust.

>> Roy
>> --
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>> Coco at maltedmedia.com
>> http://five.pairlist.net/mailman/listinfo/coco
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>Coco at maltedmedia.com

Cheers, Gene
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