[Coco] Coco RGB to SVGA

[Brian Blake]

Roy,

Put me down for a board level.

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www.tandycoco.com
www.tandycoco.com/forum
On Jun 20, 2015 4:30 PM, "Roy Justus via Coco" <coco at maltedmedia.com> wrote:

> Dear coco friends,
>
>
>       I have nearly recovered   from illness and loss of my data files
> so I am getting ready to restart production of my converter.
>
>       I also  want to discuss some aspects of the process of conversion
> of Coco RGB.     First is the noise some see with early version of my
> converter.   Most common is the vertical bands seen during use.
> Another is the distortion seen with some foreground/backround
> when viewing 80 column text.   Typically the blue in a cls(7) backround
> in SECB.   At first I tried to eliminate this noise  but had little
> success doing it.
>
>      The basic problem is this noise comes out of the GIME chip and
> not from any outside source.    The reason it didn't show up in the old
> 15 khz CRT displays is that they naturally filtered the signal due to thier
> low bandwidth response.
>
>     The second problem is that my earlier converters and other commercially
> availible units have a hard time keeping an LCD display locked.    LCD's
> have
> such highbandwith the noise coming out of the GIME confuses them and they
> shut down.
>
>     If you want to use a converter that won't sync to an LCD try it on a
> older CRT SVGA
> display.    This applys to my old units and commercially availible ones.
>
>     To  address these problems I have lowered the bandwith of my converter
> with
> some low pass filtering on both the data lines and sync inputs.    I have
> also changed
> the PLL tank circuit values to address the phase lock problems.   I have
> tried my
> new converter on no less than five "picky" LCD's and they stay on and
> sharp.
>
>      Another problem is the price of my converter.      It cost
> approximately $100 per
> unit to build but I think that is way too high.     I  am going to offer a
> board level
> unit for $40  and  a unit with enclosure for $60.   I don't do this to
> make money.
> i do it because monitors for the Coco3 are becoming very rare and I enjoy
> it.
>
>    So let's light up the summer with coco3 displays and send me your
> order for one.    A board level unit comes with all the connections for
> a great repak project and the unit in with enclosure looks good on the
> shelf with the coco3.
>
>
>
> Roy Justus
> rjrtty at aol.com
>
>
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>