[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

>>>>>>

>>>>>> --

>>>>>> Coco mailing list

>>>>>> Coco at maltedmedia.com

>>>>>> http://five.pairlist.net/mailman/listinfo/coco

>>>>>>

>>>>>>

>>>>>>

>>>>>>

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>>>>>

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