[Coco] Coco monitors 1084s-xx ?

Kip Koon computerdoc at sc.rr.com
Sun Mar 30 21:00:22 EDT 2014

Hi Gene!
That is a very interesting factoid and a very sneaky secret for a
proprietary cable.  You guys are awesome to figure that out.  

-----Original Message-----
From: coco-bounces at maltedmedia.com [mailto:coco-bounces at maltedmedia.com] On
Behalf Of Gene Heskett
Sent: Sunday, March 30, 2014 5:41 PM
To: coco at maltedmedia.com
Subject: Re: [Coco] Coco monitors 1084s-xx ?

On Sunday 30 March 2014 17:25:52 farna at amc-mag.com did opine:

> Date: Fri, 28 Mar 2014 23:45:50 -0400
> From: mike delyea <mdelyea at gmail.com>
> None of them will work.  You need to wire in a 74ls02 to change the 
> horiz/vert signal.  I have done this myself because nobody seemed to 
> know how at the time.  I spent a lot of time tracking down pinouts for 
> Amiga monitors and the signals on each wire.

A little known factoid might be fitting here.  The factory cable to run the
1084 on an Amiga, and 10's of thousands of them were, actually had that
74LS04 molded into the back molding of the DB23 plug.  I had one fail, and
when I went to ring out the cable, comparing what one end was compared to
the other, the synch line to the monitor was shorted to ground thru the
failed chip, but it looked like I was trying to measure a integrated circuit
input on the H&V sync lines from the amiga end.  I scratched my head on that
for a few minutes and decided there must be an IC hidden in the plastic
molding on the back of the db23 & started grinding away on the plastic with
a dremel.  By being very careful I was able to preserve the chips marking,
and teased it out and replaced it.  With a 74HC04.  Worked fine till the CRT
in the 1084 was so burnt we couldn't use it for fine grx work anymore.

I don't know if that was supposed to be a secret, but it sure sold a lot of
cables for commie when they didn't have anything else left to sell us.

> ==============================================
> Mike, the later models apparently sense the polarity of the H/V sync 
> or are made differently. I am aware that the 1080 needed the signals 
> inverted, but the 1084S I had worked perfectly with just a simple 
> cable matching signal pins. I posted a site with pin-out info earlier...
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Cheers, Gene
"There are four boxes to be used in defense of liberty:
 soap, ballot, jury, and ammo. Please use in that order."
-Ed Howdershelt (Author)
Genes Web page <http://geneslinuxbox.net:6309/gene>

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