[Coco] CoCo 1/2 to VGA?

[Kip Koon]

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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