[Coco] COCO3 Video

[Dave Philipsen]

And even though the schematic shows orientation of the polarity on the caps it really shouldn’t make any difference.

Dave

> On Mar 2, 2018, at 2:05 AM, David Ladd <davidwladd at gmail.com> wrote:
> 
> Also I would like to add my 2 cents worth here as well.
> 
> There is another big thing you need to check when dealing with RGB hardware
> is what the output voltage from the RGB lines are.  For example the CoCo
> 3's voltage output at full RED, GREEN, BLUE, the max voltage output will be
> 2 Volts.
> 
> Now SCART spec is 1 Volt on the RGB lines.  So when taking a CoCo 3's RGB
> line's to the SCART lines you need a 150 to 180 Ohm resistor and
> electrolytic capacitor in series to bring the voltage down to a safer level
> for the SCART input.
> 
> I used:
> http://members.optusnet.com.au/eviltim/gamescart/gamescart.htm
> 
> As a reference to some of the testing to figure out why the original CoCo 3
> RGB to SCART cable was so over powered.
> 
> The negative lead of capacitor goes towards the SCART and the positive side
> goes to the resistor.  Then the other end of the resistor goes to RGB out
> of the CoCo 3.  So you would need 3 pairs of these...  1 pair for each
> color analog line.
> 
> I hope that makes sense.
> 
> 
> 
> +-----------------------------------------------------------------------+
> | David Ladd a.k.a. PacoOtaktay a.k.a. Drencor                          |
> | YouTube: http://www.youtube.com/user/PacoOtaktay                      |
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> | G+:  https://plus.google.com/+DavidLaddPacoOtaktay                    |
> |                                                                       |
> | Do you have your CoCo 3 yet?                                          |
> +-----------------------------------------------------------------------+
> 
> 
>> On Thu, Mar 1, 2018 at 12:45 PM, Zippster <zippster278 at gmail.com> wrote:
>> 
>> Not really a standard, but does denote RGB and separate (H)sync and
>> (V)sync.
>> 
>> The CoCo3 outputs 15.7KHz analog RGB with separate, positive-going syncs.
>> 
>> I’m guessing the boards you mention are the GBS8200 and similar scan rate
>> doublers
>> to get VGA scan rates.  They’re cheap, they work, and they’re generally
>> considered a little fuzzy.
>> 
>> Other options are available like the super espectro from cloud9 and
>> Richard Lorbieski’s SCART
>> to HDMI cables that will give a much better picture.  Still, has to beat
>> RF and composite, right?  :)
>> 
>> - Ed
>> 
>> 
>>> On Mar 1, 2018, at 12:15 PM, Bill Gunshannon <
>> bill.gunshannon at hotmail.com> wrote:
>>> 
>>> 
>>> I am just full of questions today.  :-)
>>> 
>>> 
>>> There is apparently a standard (of sorts) called RGBHV.
>>> 
>>> I think it was used in video games although there does
>>> 
>>> seem to have been some attempt to get it into the home
>>> 
>>> theater market.
>>> 
>>> My questions:
>>> 
>>> Anybody here familiar with it?
>>> 
>>> is it likely that the output from the bottom of my COCO3 would match
>>> this spec?
>>> 
>>> My reason for asking is I have a board that claims to be able to convert
>>> this to
>>> 
>>> VGA.  If it were to work, these boards are really cheap ands still seem
>>> to be
>>> 
>>> available all over the web.
>>> 
>>> 
>>> Given no information I amy give it a try, but I will have to make a
>>> cable and
>>> 
>>> that may be more work than I can easily do as I expect those DB15's are
>>> 
>>> rather crowded.
>>> 
>>> bill
>>> 
>>> 
>>> 
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>> 
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