[Coco] [SPAM] Coco RGB to SVGA

[Steve Batson]

Roy,

Glad you are recovering from you illness. If I wasn't already far committed for Luis's FPGA converter, I'd probably have ordered one of yours. Best wishes as you build these, I could end up ordering one down the road.



On Jun 20, 2015, at 1:30 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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