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

[Steve Batson]

No problem, Roger deserves the credit all this work. I just duplicated
what he did and putting info here hoping it's helpful.



I had no stock of resistors and trying to find just a few either wasn't
economical or easy. Needless to say, I've got a pretty good stock now!
:D
 
> Thank you very much Steve. I should be able to
test it out today. I will

> report back either way. I might put my DigiKey order in anyway. You
can

> never have too many resistors :)

>

> On Fri, Jul 10, 2015 at 9:07 AM, Steve Batson

> <steve at batsonphotography.com>

> wrote:

>

>> John,

>>

>> No, the resistor from R7 to Pos 8 on the GPIO1 connector is what
was

>> referred to as Rx, that resistor should be 1.8K. The drawing on
Luis'

>> site

>> shows a jumper wire to fix a ground issue. If that jumper is in
place

>> after

>> all the resistors in place, you will most likely have Jitter.
There

>> should

>> be no Jumper wires installed. The jumper Luis refers to is
between R21

>> and

>> R18. I'd only install that if Jitter is present with all the
resistor

>> changes. If necessary, try it both ways, but on Roger and my
board it

>> wasn't necessary. All of these changes were Roger's findings. I
only

>> duplicated his setup and it's awesome!

>>

>>

>>

>> On Jul 9, 2015, at 10:22 PM, John B <trymyz at gmail.com>
wrote:

>>

>> > I will be testing it tomorrow. Thank you for the new
values.

>> Hopefully

>> > everything will work as intended. You refer to the
additional wires

>> not

>> > being needed. Is this the resistor from R7 to Position 8 on
GPIO1 and

>> the

>> > wire between R18 and R21?

>> >

>> > On Fri, Jul 10, 2015 at 12:56 AM, Steve Batson <

>> steve at batsonphotography.com>

>> > wrote:

>> >

>> >> John,

>> >>

>> >> Yes, this is Luis' RGB2VGA board used with the DENano
FPGA.

>> >>

>> >> Since you have just finished it, I'd test it out first
to see if you

>> see

>> >> any jitter or other problems. However Roger did a lot
of

>> investigation

>> and

>> >> found these values produce voltages in line with the VGA
Standard and

>> to

>> >> help the board properly sync from the CoCo output. I
don't have all

>> the

>> >> technical details, I just know it worked for Roger and
works for me.

>> >>

>> >> These are what Roger came up with and I simply
duplicated what he

>> found.

>> >> Also, the Variable resistor, he recommended a 10K Multi
Turn for

>> finer

>> >> control when tuning for the best appearance. Another
thing to know is

>> that

>> >> there are some additional wires recommended but they
were not needed

>> on

>> >> Roger's or my case and jitter did not go away until
removed.

>> >>

>> >> Top Left

>> >>

>> >> 82 Ohms - Grey-Red-Black-Gold-Brown

>> >> R22

>> >> R23

>> >> R25

>> >>

>> >> * * * Bottom Left

>> >>

>> >> 1.2K Brown-Red-Black-Brown-Brown

>> >> R18

>> >> R19

>> >> R20

>> >> R21

>> >>

>> >> * * * Top Right 10

>> >>

>> >> R9 47

>> >> R10 47

>> >>

>> >> 390 ohms

>> >> R1

>> >> R4

>> >> R7

>> >>

>> >> 820 ohms

>> >> R2

>> >> R5

>> >> R8

>> >>

>> >> 1.8K ohms

>> >> R3

>> >> R6

>> >> Rx (this is the resistor soldered to R7 and the GPIO1
Connector)

>> >>

>> >> * * * Bottom Right

>> >>

>> >> 2K Red-Black-Red-Gold

>> >> R17

>> >> R14

>> >> R12

>> >> R11

>> >>

>> >> 1K Brown-Black-black-Brown-Brown

>> >> R15

>> >> R16

>> >>

>> >>

>> >>

>> >>

>> >> On Jul 9, 2015, at 9:31 PM, John B
<trymyz at gmail.com> wrote:

>> >>

>> >>> Steve,

>> >>>

>> >>> Are you referring to Luis' RGB2VGA board? The reason
I ask is I

>> >> literally

>> >>> (15 min ago) just finished assmebling my board. I
used the

>> resistors

>> he

>> >>> outlined on his page under the
"Modifications" section.

>> >>> https://sites.google.com/site/tandycocoloco/rgb2vga
Are those the

>> >>> resistors that produced the video jitter? If so, can
you give us

>> the

>> new

>> >>> values that fixed the issue?

>> >>>

>> >>> Thanks,

>> >>>

>> >>> John

>> >>>

>> >>> On Thu, Jul 9, 2015 at 11:45 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!!!

>> >>>>

>> >>>> --

>> >>>> Coco mailing list

>> >>>> Coco at maltedmedia.com

>> >>>>
https://pairlist5.pair.net/mailman/listinfo/coco

>> >>>>

>> >>>

>> >>> --

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>> >>

>> >>

>> >>

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>> >>

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>>

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--

Steve Batson

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