[Coco] Re: Help using the Coco3 with a 1084S-D2 Monitor

[Gene Heskett]

On Wednesday 12 November 2003 14:31, Gene Heskett wrote:
>On Wednesday 12 November 2003 13:42, Hank wrote:
>>Torsten,
>>
>>
>>
>>I have a NTSC Coco3 with the newer Gime Chip.
>>
>>Can I make internal Adjustmets inside the 1084S-D2 Monitor?
>>
>>Hank
>
>Be extremely carefull in there Hank, there are voltages in there
> that can not only give you nasty burns, but can kill.  High voltage
> at the side of the crt is around 27 kilovolts.  Thats not normaly
> lethal unless applied directly across the chest area because its
> current limited to around a milliamp or so, but it can darned sure
> get your attention in a manner you'll remember the rest of your
> life.
>
>WRT the synch problem, I'd expect you'll have to do there what many
> of us did for the maggy monitors, which are very similar, and which
> commie did right inside the molded plug of their special amiga
> cables.  Hidden away inside that plastic db23's molding is a cmos
> (thats why its so easily damaged, an lsttl works just as well, I've
> done that) to buffer the sync signals and bring them up to about 4
> volts.  I suspect you may have to do a similar operation for the
> coco.  It was done on the amiga's because the agnus chip had
> overcurrent sensors in it that shut it down if it tried to drive
> too many 75 ohm loads.  It could drive the rgb lines ok, but add a
> 75 ohm load on the synch lines and it shut itself down.  That
> monitor has 75 ohm terminations on every signal line going into it,
> and I don't think the gime is up to hitting a low ohms load like
> that with enough voltage to make the monitor see it.  And its
> probably warming up the gime trying, which isn't good for a chip
> thats almost made out of unobtainium today.
>
>Any old NAND gate, used 2 in series so the polarity isn't changed,
>should do it just fine.
>
>On the box box amiga's, tehre was a 5 volt powered pin to supply
> that chip, but I don't recall if the coco3 can be rigged to do that
> or not.

Darn these ancient fingers, they never do as they're told anymore, 
that should be "big box amiga's, there" and a 4k isn't a big box, but 
a 500 is.  Don't ask...


>>PS: are far as the NEC-3Ds goes, I found those RBG Gounds on pinds
>> 6,7, and 8 do not need to be connected when hooking it up to the
>> Coco3.  It works great just using any of the ground pins.
>>
>>----- Original Message -----
>
From: "Torsten Dittel" <Torsten at Dittel.info>
>
>>To: <coco at maltedmedia.com>
>>Sent: Wednesday, November 12, 2003 6:13 AM
>>Subject: [Coco] Re: Help using the Coco3 with a 1084S-D2 Monitor
>>
>>> Hi Hank,
>>>
>>> > You guys have any ideas on this one?
>>>
>>> I checked your pin out on all 3 components and it looks OK (just
>>> to complete it, pins 6,7,8 on the NEC 3D are the GND lines for
>>> R,G,B).
>>>
>>> I noticed "glitches" in vertical sync on my 1084S-P1 (AFAIR the
>>> only difference between the P1 and the D2 is a head phone jack)
>>> too. The funny thing is that it's only with one of my two (PAL)
>>> CoCo3s. Both work fine with the NEC 3D. One of the CoCo's is
>>> US-made, the other Korean. The difference is, that the (newer) US
>>> model has a new version of the GIME chip and I guess this is
>>> causing the problems because of slightly different signal timing
>>> and/or amplitudes. I never cross-changed the GIME chips nor
>>> checked it out with an oscilloscope.
>>>
>>> Hope this helps.
>>>
>>> Regards,
>>> Torsten from Germany
>>>
>>>
>>> --
>>> Coco mailing list
>>> Coco at maltedmedia.com
>>> http://five.pairlist.net/mailman/listinfo/coco
>
>--
>Cheers, Gene
>AMD K6-III at 500mhz 320M
>Athlon1600XP at 1400mhz  512M
>99.27% setiathome rank, not too shabby for a WV hillbilly
>Yahoo.com attornies please note, additions to this message
>by Gene Heskett are:
>Copyright 2003 by Maurice Eugene Heskett, all rights reserved.

-- 
Cheers, Gene
AMD K6-III at 500mhz 320M
Athlon1600XP at 1400mhz  512M
99.27% setiathome rank, not too shabby for a WV hillbilly
Yahoo.com attornies please note, additions to this message
by Gene Heskett are:
Copyright 2003 by Maurice Eugene Heskett, all rights reserved.