[Coco] *COOL* Look what I found! (VideoMod for CoCo2)

[George Ramsower]

http://sunpal7.mit.edu/6.111/mc6847/6847.pdf
Here is the data sheet on the 6847. On the bottom of pp. 12 there is a 
sample ckt for connecting the MC1372 to a composite monitor. It only uses 
two transistors
It's been many years since I connected a coco to a TV bypassing the RF 
circuitry. I'm pretty certain pin 12 was where I picked up the video. From 
there, I think I had one transistor to invert the signal and then injected 
in the video detection point on the B&W TV set. I do remember seeing pixels 
for the first time. The image was perfectly sharp.

George
----- Original Message ----- 
From: "N8WQ" <exwn8jef at gmail.com>
To: "CoCoList for Color Computer Enthusiasts" <coco at maltedmedia.com>
Sent: Thursday, January 08, 2009 12:27 PM
Subject: Re: [Coco] *COOL* Look what I found! (VideoMod for CoCo2)


> Hi Fedor,
> Your board is clearly a "through hole" project.
> I can see the 4 transistors, variable cap and potentiometer on the circuit 
> board.
> That looks like a nice project for the CoCo.
>
> Alan Jones
>
> -- 
> N8WQ - Canal Winchester, Ohio
> http://exwn8jef.googlepages.com/home
> http://n8wq.blogspot.com
>
>
>
> Fedor Steeman wrote:
>> Hi all,
>> Well, there is definitely a little board to be added, but I do not know 
>> the
>> technical jargon for this technique. Of the modified CoCo2 I possess that
>> has this videomod, I added a range of pictures to my gallery on
>> coco3.comfor the interested to peek at:
>>
>> http://coco3.com/modules.php?name=Gallery&g2_itemId=1483
>> <http://coco3.com/modules.php?name=Gallery&g2_itemId=1483>
>>
>> Cheers,
>> Fedor
>>
>> PS: Nobody interested in the SCART connector? :-(
>>
>> 2009/1/8 N8WQ <exwn8jef at gmail.com>
>>
>>
>>> Hi George,
>>> The last time I looked the Color Computer (1, 2, or 3) didn't have any
>>> surface mount components. LOL
>>> The circuit has 22 parts, which includes one variable capacitor and one
>>> potentiometer.
>>> If you look on page one you can read "SMD technick."
>>> He clearly shows the circuit raised on top of the rf video modulator.
>>>
>>> Alan Jones
>>>
>>> --
>>> N8WQ - Canal Winchester, Ohio
>>> http://exwn8jef.googlepages.com/home
>>> http://n8wq.blogspot.com
>>>
>>>
>>>
>>> George Ramsower wrote:
>>>
>>>
>>>> ----- Original Message ----- From: "N8WQ"
>>>>
>>>>  Hi Fedor,
>>>>
>>>>> That looks like a SMT (surface mount) component layout. A SMT pc board
>>>>> would have to be made or you could use what us home brewer's call 
>>>>> "manhattan
>>>>> style" construction. Or we could translate the project to "through 
>>>>> hole"
>>>>> components. It would be nice to see the schematic though. LOL
>>>>> The BSR14 is a NPN general purpose amplifier.
>>>>>
>>>>> Alan Jones
>>>>>
>>>>>
>>>> He's showing where on the RF modulator to make connections. The ckt he
>>>> built only has about three or four parts on it.
>>>> Usually this mod only require a transistor to invert and amplify the 
>>>> video
>>>> that goes into the modulator.
>>>> Although I can't read what he's said, it looks to me to be an 
>>>> installation
>>>> guide for the little ckt. This is probably why there's no schematic of 
>>>> the
>>>> actual ckt.
>>>>
>>>> George
>>>>
>>>>
>>>>>
>>>>> Fedor Steeman wrote:
>>>>>
>>>>>
>>>>>> Hi all,
>>>>>>
>>>>>> While going through the huge lot of copied CoCo Manuals I inherited 
>>>>>> from
>>>>>> Michel Collette, a former Dutch CoCo-society regional coordinator, I
>>>>>> discovered the following schematics for making a video buffer mod for
>>>>>> the CoCo2, enabling a CoCo2 to be coupled up any television or video
>>>>>> equipment with a composite video input:
>>>>>>
>>>>>> http://www.steeman.dk/CoCoManuals/VideoMod_(KoenVaartjes).pdf
>>>>>>
>>>>>> How cool is that!?
>>>>>>
>>>>>> It is all in Dutch, written by someone called Koen Vaartjes, but if
>>>>>> people
>>>>>> are interested I could translate, clean it up, perhaps redo the
>>>>>> schematics
>>>>>> in a graphics editor and put it up on a webpage!
>>>>>>
>>>>>> Some of the equipment i inherited from Michel Collette actually 
>>>>>> included
>>>>>> a
>>>>>> CoCo2 with this video mod. I tried it out when I first discovered it 
>>>>>> and
>>>>>> it
>>>>>> worked flawlessly then. After having transported the CoCo one time,
>>>>>> however,
>>>>>> something went wrong, because after that all I got was a black screen
>>>>>> and no
>>>>>> sound. I believe there must be a loose contact somewhere, because 
>>>>>> every
>>>>>> now
>>>>>> and then when I try it, it works again.
>>>>>>
>>>>>> The final page looks like a schematic of a scart cable (
>>>>>> http://en.wikipedia.org/wiki/Scart) that is widely used in Europe at
>>>>>> least.
>>>>>> I do also have a modified SCART cable that can be used to hook up the
>>>>>> RGB-output of a CoCo 3 to a normal television with a scart input. 
>>>>>> That
>>>>>> too
>>>>>> once worked, but not anymore. Maybe if someone could help me 
>>>>>> understand
>>>>>> the
>>>>>> schematic, and figure out what wires of a RGB-cable should be 
>>>>>> connected
>>>>>> to
>>>>>> what pin of the scart, I could try to fix the cable or make a few 
>>>>>> more
>>>>>> for
>>>>>> anyone interested... This would mean that a CoCo3 could be connected
>>>>>> from
>>>>>> the RGB output directly to a television with scart input.
>>>>>>
>>>>>> Cheers,
>>>>>>
>>>>>> Fedor
>>>>>>
>>>>>> --
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>>>>>> Coco at maltedmedia.com
>>>>>> http://five.pairlist.net/mailman/listinfo/coco
>>>>>>
>>>>>>
>>>>>>
>>>>>>
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