[Coco] RGB2VGA converter setup issue

[Barry Nelson]

Specifically, your TV does not support 640x480 on it's VGA input. It's specifications state the VGA input supports:

SVGA    800 x 600
XGA     1024 x 768      
WXGA    1280 x 800

The "VGA" input has no support for 640x480. This is becoming more and more common, and thus is one of the many reason I developed my SCART cable to HDMI converter idea.

For your TV:

Compatible Modes
TV Tuner*: NTSC/ATSC
YPbPr: 480i, 480p, 720p, 1080i
HDMI: 480i, 480p, 720p, 1080i, 1080p
PC: SVGA, XGA, WXGA
Optimum Resolution: 1920 x 1080
Begin shameless plug (again)

So a HDMI 1080p or 720p up scaler should work, or even native 480i on HDMI, but 640x480 on the VGA input will not. It also does say that the component input supports 480i, so if you converted your CoCo 3 RGB signal to YPbPr component with no change in resolution you should be able to feed that to the component input on this TV and it should work in this case. On my TV 480i is not supported on my component input, only 480p and up so that would not work for me.

My suggestion, if your TV or display has a HDMI input, use my solution, it should work and it's cheaper, provided you don't mind soldering a cable. :) And NO I will NOT be selling cables. I MIGHT build make one in trade for something I want, maybe. Otherwise, all the information to make the fairly simply cable and what adapters it should be hooked to is available at: https://hackaday.io/project/7366-coco-3-rgb-to-scart-to-hdmi-cable

Anyone else who does try this please let me know. I am fairly certain you should get good results since it feeds the CoCo 3's signal into a commercial up scaler/converter, is electrically exactly what the converter is expecting to see, and the output from the converter is upscaled to 1080p, which any modern TV or display with an HDMI input should easily recognize, but I am still curious to hear back and confirm this for more different types of TV's, etc. I have personally tried this on several TV's and displays and so far it has worked every time. I have not tried converting the HDMI to VGA, but that should work as well, and commercial adapters to do this are available for less than $10 if you don't have a HDMI input, just VGA. I suspect that should work as well, but would especially like to hear back from anyone who tries that to confirm that it is also an option. Total cost of all parts including even a VGA output converter is <$60, and only minimal soldering is required, just a cable with one resistor and a 5V power supply, no PC boards, chips, or other active components.

End shameless plug (again)

Please do not misinterpret this to mean that I dislike the other options, or that I think that they don't have utility, but I do think in many cases my solution will work well and is less expensive.

Besides, I really really do want to hear from others using my cable idea. :)

> Date: Thu, 22 Oct 2015 22:25:02 -0500
> From: Sean <badfrog at gmail.com>
> To: CoCoList for Color Computer Enthusiasts <coco at maltedmedia.com>
> Subject: Re: [Coco] RGB2VGA converter setup issue
> Message-ID:
> 	<CAFuVrczPofH-yVMpRiA8JUW5GkxnMuJJ5i9MyVTKZmwt7v0nfA at mail.gmail.com>
> Content-Type: text/plain; charset=UTF-8
> 
> I believe the cheapo TV just didn't like it.  I plugged in a Dell LCD
> monitor, and it works great!
> 
> Model is a Westinghouse, model LD-2240.
> 
> Specs page says SVGA, XGA, WXGA:
> 
> http://westinghouseelectronics.com/discontinued/led-hdtv/up-to-28/ld2240/
> 
> Sean
> 
> 
> On Thu, Oct 22, 2015 at 8:15 PM, Zippster <zippster278 at gmail.com> wrote:
> 
>> Hi Sean,
>> 
>> It sounds like it doesn’t like the scan rate.  I haven’t heard of anything
>> like this yet.  I’m using LCD TV’s with VGA ports.
>> 
>> I know sometimes TV’s don’t support all VGA modes, but 640x480 is a
>> very basic one.  What model of TV?
>> 
>> - Ed
>> 
>> 
>> 
>>> On Oct 22, 2015, at 7:56 PM, Sean <badfrog at gmail.com> wrote:
>>> 
>>> FINALLY got the time to hook up the CoCo and try out the RGB2VGA
>> converter
>>> I got from Zippster's run back in September.
>>> So far all the monitor does is say "not supported".  So it's definitely
>>> giving a signal, because when I unplug power to it, the monitor goes back
>>> to 'no signal'.
>>> 
>>> I'm using an 1080P HDTV with the VGA input.
>>> 
>>> Should I try turning the potentiometer?  Or could this be the Pin 9 topic
>>> everyone has mentioned?  I've only tried one VGA cable so far, but I know
>>> it's a good cable.
>>> 
>>> Sean
>>> 
>>> --
>>> Coco mailing list
>>> Coco at maltedmedia.com
>>> https://pairlist5.pair.net/mailman/listinfo/coco
>> 
>> 
>> --
>> Coco mailing list
>> Coco at maltedmedia.com
>> https://pairlist5.pair.net/mailman/listinfo/coco
>> 
> 
> 
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