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

[Edward Snider]

In that case I guess I'll have to change those resistors as well.

Electrolytics are well sealed, no problem there.  A transformer might take
a while to dry out, I think I might avoid dunking that.  For the rare
component that can't be submerged I usually finish the board except for
those, clean the board, add those components and spot clean where they were
installed.

- Ed
On Jul 10, 2015 11:34 PM, "Steve Batson" <steve at batsonphotography.com>
wrote:

> Ed, the recommended resistors do not provide the proper voltage levels for
> the VGA circuit, that's what Roger found out after much painful research
> and experimenting. Neither of our boards were stable with the design
> recommended voltages. With Roger's recommendation, Both Roger's and mine
> are Rock Solid.
>
> I have the 91% Isopropyl myself, a little dispenser and a small acid
> brush...works good, but I like our idea about soaking the board for a
> bit...that might not be a good idea for all components would it?
> Electrolytic caps, transformers, etc. Way back when, I used to use
> denatured alcohol with the acid brush and it worked awesome.
>
>
> On Jul 10, 2015, at 8:05 PM, Zippster <zippster278 at gmail.com> 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.
> >
> > - 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.
> >>
> >>
> >
> >
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