[Coco] CoCo 1/2 to VGA?

[Retro Canada]

you're right the Y is composite and very old school. for better results use the Y as s-video luma and you have a perfect monochrome image.

Sent from my iPhone

On 2013-03-08, at 11:57 PM, "Kip Koon" <computerdoc at sc.rr.com> wrote:

> Luis,
> The Y output portion of your schematic looks very similar to a composite
> video schematic for the Coco 2 that I put together a while back.  I got it
> from a one page article I found on the internet shortly after I joined this
> Coco List of ours.  RS sold me a bag of 25 NPN transistors (don't remember
> the number) that had PNPs mixed in which I was not aware of.  Needless to
> say, my implementation of the circuit did not work with a pnp transistor in
> the circuit as the second transistor had all the wrong voltages.  I
> connected the output of the first transistor to a cable and to a composite
> video input of an old Monitor I have, and it worked fine (if I remember
> correctly).  The first transistor was functioning correctly as all the
> voltages measured correctly on my fluke meter.  I got very disgusted with RS
> and made them make good on the transistors.  I brought my fluke meter with
> me since it has an NPN & PNP transistor mode and measured each and every
> transistor Before buying them.  I finally got my 25 NPN transistors, but
> oddly enough, I never went back to finish the circuit.  I should finish that
> thing and now I can provide Component Video Out on my Coco 2!  Now that is
> pretty Cool!  I'll have to dig out that big old CRT with Five BNC connectors
> on it and see if it will work.  In the meantime, I'll use my little
> Composite Video Monitor from yesteryear.  I could use the composite video
> input of our big screen TV!  The Coco 3 composite video output worked great
> on it!  Hummmm!
> Kip
> 
> -----Original Message-----
> From: coco-bounces at maltedmedia.com [mailto:coco-bounces at maltedmedia.com] On
> Behalf Of Luis Antoniosi (CoCoDemus)
> Sent: Friday, March 08, 2013 3:11 PM
> To: CoCoList for Color Computer Enthusiasts
> Subject: Re: [Coco] CoCo 1/2 to VGA?
> 
> here is the schematic:
> 
> https://twitter.com/RetroCanada76/status/299203476859260929/photo/1
> 
> some results:
> 
> https://twitter.com/RetroCanada76/status/299157117712093184/photo/1
> https://twitter.com/RetroCanada76/status/299157487767146498/photo/1
> https://twitter.com/RetroCanada76/status/299157331688697856/photo/1
> 
> On Fri, Mar 8, 2013 at 3:07 PM, Michael Graham <mkgraham at gmx.com> wrote:
> 
>> Sorry about the blank message, I must really learn not to hover my 
>> mouse over the 'send' button.
>> 
>> Anyway, I'm sorry I missed that, and I'll look for it shortly. The TV 
>> and the monitor both take YPbPr in low resolution, which, as far as I 
>> can tell, is identical to YCbCr (I've built an RGB to YCbCr transcoder 
>> that gave nearly perfect results on my TV).
>> 
>> -Michael
>> 
>> On 03/08/2013 02:03 PM, Luis Antoniosi (CoCoDemus) wrote:
>> 
>>> I did it and posted here the schematics few weeks ago. Search for 
>>> pristine image on coco1/2. But is a YCbCr your TV/monitor must 
>>> support that in low resolution.
>>> 
>>> On Fri, Mar 8, 2013 at 3:01 PM, Michael Graham <mkgraham at gmx.com> wrote:
>>> 
>>> So wait, does that mean you'd be able to get component video out of 
>>> a
>>>> late
>>>> model CoCo 2 with a few video amps?  I'd like to try that.  I mean, 
>>>> I doubt it'd work on a modern LCD TV or anything, but I have a CRT 
>>>> TV and a CRT monitor that can both take low-resolution component 
>>>> video and display it quite well.  The monitor could probably do it 
>>>> even if it isn't quite at the right standard (it's a Sony PVM and 
>>>> has lots of adjustments).
>>>> 
>>>> -Michael
>>>> 
>>>> On 03/08/2013 12:12 PM, John W. Linville wrote:
>>>> 
>>>> On Thu, Mar 07, 2013 at 12:43:13AM -0600, camillus Blockx wrote:
>>>>> 
>>>>> Well the rf modulater works with composite video. You can take 
>>>>> that
>>>>>> signal
>>>>>> after amplified it and end it to 75 Ohm to feed your a/v device. 
>>>>>> Look on google to find schematic for amp. Know for shure there is 
>>>>>> one that works on coco 2. Used it on my coco 2 myself.
>>>>>> 
>>>>>> That is true on the CoCo1, but not really true on the CoCo2.  On 
>>>>>> the
>>>>> CoCo2, the Y, R-Y, and B-Y signals from the 6847 go to the modulator.
>>>>> The MC1372 inside the modulator combines them into the NTSC RF signal.
>>>>> 
>>>>> The CoCo1 uses an MC1372 as well, but only to generate NTSC 
>>>>> composite video which is then fed to a separate RF modulator.  That 
>>>>> is why it is easier to convert a CoCo1 to composite video out than 
>>>>> it is to do so for a CoCo2.
>>>>> 
>>>>> John
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> 
> 
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