[Coco] CoCo2 lower graphics

[Zippster]

If it’s an American motherboard CoCo2 (channel switch over the RF jack),
the MC6847 should be socketed.  A bad 6847 or something with the 6847
control/address lines does come to mind.

If it’s a socketed VDG, pulling and reseating it might do the trick.
I’d try that first. All socketed chips actually.

- Ed


> On Jun 16, 2016, at 7:15 PM, Michael Pittsley <mikep at twcny.rr.com> wrote:
> 
> I have a COCO 2 that when I load certain software or cartridges the bottom
> half the screen is garbled.   Knowing very little about the CoCo's hardware
> I'm hoping someone may be able to assist me.  The garbled graphics is just
> on some graphical games / cartridges.  If I load Tom Mix's Donkey King
> everything works as expected.  Try to run a frogger game or Bridge Tutor, I
> cannot see the bottom half of the screen other than gibberish graphics.  Now
> I have another CoCo 2 that is essentially used for parts, only because when
> I turn it on, I get a green screen but no "OK" screen.  Is there a video
> chip in the CoCo 2 I can easily remove and replace with one from the parts
> CoCo?  
> 
> 
> 
> -          Michael Pittsley
> 
> -          Update NY
> 
> 
> -- 
> Coco mailing list
> Coco at maltedmedia.com
> https://pairlist5.pair.net/mailman/listinfo/coco