[Coco] [Color Computer] COCO II A/V Mod

[Fedor Steeman]

I found it myself now. The title of my original message was: "*COOL* Look
what I found! (VideoMod for CoCo2)"

This is the link to the scanned in doc:
http://www.steeman.dk/CoCoManuals/VideoMod_(KoenVaartjes).pdf

As said, I wanted to translate it and tidy it up, unless you can figure it
out as such of course! :-)

Cheers,
Fedor

On 29 May 2012 11:36, Fedor Steeman <petrander at gmail.com> wrote:

> Hi!
>
> I actually have some old documentation for doing precisely that that I
> wanted to scan in, translate from Dutch and post online for a long time but
> never got around to do it. I can revive the effort if you're interested!
> Just let me know...
>
> I also have a CoCo2 that has that mod with composite video output, but it
> no longer works (probably some short circuit). If you search the CoCo
> mailing list for my name and the proper keywords you may find this earlier
> discussion.
>
> Cheers,
>
> Fedor Steeman
>
>
> On 26 May 2012 06:21, Computer Doc <computerdoc at sc.rr.com> wrote:
>
>> Double check to make sure both transistors are functioning correctly.  I
>> need some HP oscilloscope probes, so I can't verify your 20mV measurement,
>> but if you have the correct DC voltage on each transistor pin minus the
>> voltage drop across each transistor junction then your circuit should
>> work.
>> It seems like I remember output video rms voltage is very small like 1V
>> peek-to-peek.  Video Circuits are not my forte but a close friend of mine
>> has taught me quite a bit over the decades.  It would seem to me that
>> 20mVs
>> is just too small to effectively produce a good video image on a composite
>> video monitor if any at all.  Also make sure that you soldered the color
>> monitor driver circuit to the correct pins of the MC1372 IC.  The
>> following
>> is another link (the original I can't find) of the same simple color
>> monitor
>> driver circuit that produces a composite video output for the color
>> computer
>> that I used.  When I built it, mine would not work either.  I got to
>> checking DC voltages to make sure the transistors were turned on and it
>> turned out that the final NPN was not turned on!?!.  I suspected Radio
>> Shack
>> must have sold me a bag full of NPNs that must have had some PNPs mixed in
>> with them.  It turned out that MOST (12 out of 15!) transistors in the bag
>> was PNPs!  It was labeled NPNs!  I got the transistors switched out, but I
>> have not gotten back to replacing the PNP with an NPN yet.  It's so
>> simple I
>> should have done it already, but I have been busy building a Motorola
>> 6802/6846 microprocessor & ROM, I/O, Timer based computer system that I
>> had
>> started way back in college. I never finished it because the project was
>> too
>> overwhelming and I did not have enough time to complete it. I've been
>> reinspired to tinker with 8-bit microprocessors again and I just have not
>> gotten back to repairing my composite video driver circuit.  I have my
>> color
>> monitor driver circuit  connected to my Coco 2 also.  I pray you find the
>> problem so you can enjoy your Coco 2 also.  Happy Computing!
>>
>> Kip Koon
>>
>> Here's the link:
>> http://coco_docs.tripod.com/id53.htm
>>
>>
>> -----Original Message-----
>> From: coco-bounces at maltedmedia.com [mailto:coco-bounces at maltedmedia.com]
>> On
>> Behalf Of Ale Smukler
>> Sent: Friday, May 25, 2012 9:40 AM
>> To: ColorComputer at yahoogroups.com
>> Subject: [Coco] [Color Computer] COCO II A/V Mod
>>
>> Hi! I'm an argentine Home Computers collector and am interested in adding
>> a
>> audio / video composite outputs to a COCO II (my model is a "melted
>> keyboard" one). I saw that there exists a circuit, but I can't find it!.
>> Could you help me, please?
>>
>> Muchas gracias!
>>
>>
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>>
>>
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>
>