[Coco] Cross Post from the Facebook Page about the RGB2VGA Board

Sun Jul 19 22:15:51 EDT 2015

If you’re running without the ground fix (much more stable), and Roger’s resistor
values, I think that is about as good as it gets with this particular PCB without
improvements to the FPGA code.

Although I seem to be able to dial in an acceptable screen for any mode no problem,
but finding one that’s perfect across all of them…. well, I guess it is what it is.

Still darn good though.  :)

- Ed

> On Jul 19, 2015, at 9:02 PM, John B <trymyz at gmail.com> wrote:
> 
> I did both.  The ground fix makes the text more unstable.
> 
> On Sun, Jul 19, 2015 at 10:00 PM, Zippster <zippster278 at gmail.com> wrote:
> 
>> Hi John,
>> 
>> Are you running with or without the ground fix on the hsync input?
>> 
>> - Ed
>> 
>> 
>>> On Jul 19, 2015, at 8:41 PM, John B <trymyz at gmail.com> wrote:
>>> 
>>> Steve,
>>> 
>>> I built a second board this weekend with the new resistor values.  Your
>>> sheet was quite handy.  Thank you again.  The text has definitely
>>> stabilized but a few other things are off.  The left edge of the screen
>> is
>>> kind of wavy and gray lines are wavy.  For example in KQ3, everything
>> else
>>> is stable, except the gray lines (lines in the stairs and wall).  They
>> seem
>>> to shimmer.  I have adjusted the potentiometer but going to far either
>> way
>>> causes other issues with the image.  I know you recommeneded a multi-turn
>>> potentiometer.  Which one are you using?  Anyway, I will most likely try
>> a
>>> higher quality monitor and see if the image improves.  Currently I am
>> using
>>> a cheap Dell 17 inch that was in the attic.  Maybe I am being too picky
>> and
>>> this is as good as it gets.
>>> 
>>> John
>>> 
>>> On Sun, Jul 12, 2015 at 4:53 PM, John B <trymyz at gmail.com> wrote:
>>> 
>>>> I am pretty sure it will stabilize with new resistor values.  Compared
>> to
>>>> composite, it looks pretty darn good now.  OSH Park only sold the
>> boards in
>>>> lots of 3 so I have 2 spares.  I will definitely complete the other one
>>>> with the new values.  Haven't decided if I will build the third one yet.
>>>> 
>>>> On Sun, Jul 12, 2015 at 1:04 AM, Steve Batson via Coco <
>>>> coco at maltedmedia.com> wrote:
>>>> 
>>>>> John,
>>>>> 
>>>>> Trust me, unless you have something else wrong with the board, Roger's
>>>>> recommended resistor changes will clean things right up. Mine looks
>> awesome
>>>>> and I simply duplicated his changes. Since I had a few resistor
>> changes, I
>>>>> may end up buying another board and building one up fresh with the
>> right
>>>>> resistors the first time. The board will certainly look better and it
>> won't
>>>>> hurt to have a spare. I'm not going to buy a spare FPGA
>>>>> though...hehehehe...that's a bit pricey.
>>>>> 
>>>>> On Jul 11, 2015, at 9:48 PM, John B <trymyz at gmail.com> wrote:
>>>>> 
>>>>>> Definitely great news.  Hopefully the new resistors will take care of
>> my
>>>>>> jitter/wavy lines and text problem.  I will find out next week.
>>>>>> 
>>>>>> On Sun, Jul 12, 2015 at 12:42 AM, Steve Batson via Coco <
>>>>>> coco at maltedmedia.com> wrote:
>>>>>> 
>>>>>>> I changed the last 4 resistors and didn't really notice much
>>>>> difference,
>>>>>>> but since values were based on Roger's research and testing and that
>>>>> his
>>>>>>> board is now solid, I figured I'd do the same. I've Tested all of the
>>>>>>> features and it's incredible results.
>>>>>>> 
>>>>>>> The output is rock solid. Colors are Rich. Text looks fantastic in
>> 32,
>>>>> 40
>>>>>>> and 80 columns. I've tested Zaxxon, Grabber, Tetra3, Brewmaster,
>> Donkey
>>>>>>> King. And The biggie, Sockmaster's port of the Original Donkey Kong
>>>>> and it
>>>>>>> Looks Awesome! Very happy with the results of this thing. It was a
>> lot
>>>>> of
>>>>>>> work, but it was well worth it.
>>>>>>> 
>>>>>>> 
>>>>>>> 
>>>>>>> 
>>>>>>> On Jul 9, 2015, at 8:45 PM, Steve Batson <
>> steve at batsonphotography.com>
>>>>>>> wrote:
>>>>>>> 
>>>>>>>> I figured I'd post the following here too. Some discussion occurred
>> on
>>>>>>> the FB page, but a lot of discussion was done between Roger and
>> Myself
>>>>> in
>>>>>>> email as Roger made several discoveries that stabilized some very
>>>>> annoying
>>>>>>> jitter problems with video.
>>>>>>>> 
>>>>>>>> RGB2VGA Stabilized!
>>>>>>>> First thanks to Felipe for a very cool Solution to bring the CoCo3
>>>>> video
>>>>>>> to Modern VGA Monitors. Originally, I missed a few resistors that I
>>>>> somehow
>>>>>>> thought were optional and Felipe straightened me out on those.
>>>>>>>> Then I was getting Jitter just like Roger was experiencing. I had
>>>>>>> several email discussions with Roger as he was doing some research
>> and
>>>>>>> experimenting based on what he found about the VGA standards and
>> found
>>>>> that
>>>>>>> changing some resistor values stabilized the output from his board. I
>>>>> have
>>>>>>> pretty much duplicated Roger's resistor values on my board with the
>>>>>>> exception of 4 that I'm waiting to come in, but mine is crisp and
>>>>> jitter is
>>>>>>> gone. I will most likely change those 4 resistors when the parts come
>>>>> in
>>>>>>> unless it doesn't make sense.
>>>>>>>> Anyway, Finally fantastic output on my VGA monitor. Very Cool!!!
>>>>>>>> Very Big thanks to Roger!!!
>>>>>>>> 
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