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

[Gene Heskett]

On Friday 10 July 2015 23:05:56 Zippster wrote:
> I’m following this thread with interest, as I’m going to be finishing
> up theRGB2VGA boards that people had ordered from Kip to get that
> project successfully completed.
>
> It is true that different monitors are more or less tolerant to
> certain differences in signals, that could explain some of what is
> being seen here.
>
> Regarding cleaning boards, 91% isopropyl alcohol works wonderfully. 
> What I do is submerge the boards in the iso in a small tupperware type
> container, soak for 10 minutes or so, brush them with a toothbrush
> while in the bath, then rinse with fresh iso and air dry. Be sure to
> use the 91%, the lower concentrations have too much water in them. 
> It’s available at drug stores, walmart, etc.

Even better is the alcohol sold at paint stores.
>
> - Ed
>
> > On Jul 10, 2015, at 9:39 PM, Steve Batson
> > <steve at batsonphotography.com> wrote:
> >
> > John,
> >
> > Have you changed the resistors yet, or are you using the resistors
> > recommended for the design? I was seeing jitter, where the entire
> > screen would jerk and occasional waves going through it mostly
> > noticeable on the edges. Also, it didn't seem consistent, sometimes
> > it was worse than others. Based on what Roger had found, it sounded
> > like there were a number of issues being caused by the original
> > resistor values. Voltage Levels were not what they should be. Also
> > there was issues with the HSYNC and VSYNC again caused by original
> > resistor values. Luis and posted on the FB page a response to one of
> > my questions that some CoCo's are noisier than others and this may
> > very well be true, but I'd guess symptoms could be worse on some
> > systems then others which could be the combination of the CoCo and
> > Monitor. From discussions with Roger about this and how he fixed it,
> > I'm going to go out on a limb here and suggest that with his
> > suggested resistor values, the video will most likely be crisp,
> > clean and jitter free on most any CoCo and VGA monitor unless they
> > have problems of their own.
> >
> > It was a bit of a pain in the butt pulling a bunch of resistors out
> > and replacing them with Rogers suggested values, but I'd highly
> > recommend it if you haven't done so already. It was totally worth
> > it! If you have already replaced the resistors with the new values
> > and are still having issues, I'd suggest the following:
> >
> > 1) Inspect your board and make sure you have no possible shorts.
> > Clean it real good with alcohol or other good electronic board
> > cleaner and thoroughly dry. 2) Check all the cables including power
> > going to the board and make sure all is well 3) Make sure the ribbon
> > cable isn't right next to a transformer including the CoCo power
> > power supply (thought I am not having issues even if set the board
> > right on top of the CoCo above the transformer). This probably is
> > NOT an issue. 4) Remove wire I mentioned that was a ground fix.
> >
> > Anyway, let me know if you have changed the resistors yet or not.
> > I'm very curious to see where you are at.

Cheers, Gene Heskett
-- 
"There are four boxes to be used in defense of liberty:
 soap, ballot, jury, and ammo. Please use in that order."
-Ed Howdershelt (Author)
Genes Web page <http://geneslinuxbox.net:6309/gene>