[Coco] Color blind coco1 :(

[Luis Antoniosi (CoCoDemus)]

I touched when I was regulating a color trimpot



On Sun, Oct 20, 2013 at 1:37 PM, Chad H <chadbh74 at hotmail.com> wrote:

> Do you work on the parts while they are powered?  Naughty naughty
>
> -----Original Message-----
> From: coco-bounces at maltedmedia.com [mailto:coco-bounces at maltedmedia.com]
> On
> Behalf Of Luis Antoniosi (CoCoDemus)
> Sent: Sunday, October 20, 2013 12:33 PM
> To: CoCoList for Color Computer Enthusiasts
> Subject: Re: [Coco] Color blind coco1 :(
>
> I found the problem: VDG. I have 2 busted VDGs damn! I dessoldered the VDG
> from another coco2 and it works green and beautiful :)
>
>
>
>
> On Fri, Oct 18, 2013 at 10:32 AM, Luis Antoniosi (CoCoDemus) <
> retrocanada76 at gmail.com> wrote:
>
> > Hi guys,
> >
> > I was doing a composite board (using the vdg 6847 scheme) for the
> > mc1372 on my coco1. It was working but I accidentaly touched a
> > resistor (mc1372 pin 14) connected to +5V to the RF metal can. It
> > reset and since them the colors are all screwed.
> >
> > Instead of green text I have a brown/pink and even the green pmode 3
> > seems brown. Even the s-video driver gets brownish colors.
> >
> > -I replaced the mc1372 and the mc6847 with no avail same result.
> > -I checked the color lines from 6847 and they are fine.
> > -Replaced the 104 cap on the chroma bias between 6847 and 1372 same
> thing.
> > -Turning the color burst trimmer has no effect. I even replaced the
> > xtal and the colors are the same.
> >
> > The computer works fine, only the colors are messed up. I suspect now
> > the caps in the clock line but I'm not sure anymore. Do you guys have
> > any clue on what should I check ?
> >
> > Notice that this computer never had the PMODE4 artifact colors
> > (red/blue) correct. They were always green/pink or cyan/crimson. But
> > now the colors are screwed up this freaking computer show these colors as
> red/blue! DAMN!
> >
> > This is a F board coco1. There is the "fix-in-a-noodle" over the
> > mc1372 that goes exactly on vdg clock line. But my fix seems to be
> > different. I tried disconnecting this "bridge" again no difference.
> >
> > see the fix I have (i removed the noodle for the photo):
> >
> > pic.twitter.com/wME0rAp4Yp <http://t.co/wME0rAp4Yp>
> >
> >
> > Any help is appreciated,
> >
> > Thxs,
> >
> > --
> > Long live the CoCo
> >
>
>
>
> --
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>
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