[Coco] Color blind coco1 :(

[Chad H]

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
>



--
Long live the CoCo

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