[Coco] CoCo2 lower graphics

[Michael Pittsley]

I'm not really sure how to respond to these messages on here.  I hope I have
it right.  Anyhow.  Running screen0,1 goto 10 doesn't do much.  From the TV
I have the CoCo connected to, it presents an orange line that runs up and
down the screen until I press break.   I attempted to attach screen shots;
however they proved to be too large to post on here. 

 

The CoCo that is having the issue has the XC80652P VDG chip (This chip is
said to have been pre-release parts).  I reseated this chip and there was no
difference.  I also replaced the VDG chip with a MC6847P chip from another
CoCo.  Either these two chips are not compatible or the chip from the spare
parts computer is also broken.  Either way replacing the chip with the one I
had didn't resolve my issue.

 

Any suggestions will be appreciated.

 

_____________________________________________________

"Michael Pittsley" wrote:

> I have a COCO 2 that when I load certain software or cartridges the 

> bottom half the screen is garbled. [...] 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.

 

Might be worth a photo of the garbled screen.  The games otherwise seem to
be running as expected?  Weird failure mode!

 

What happens if you type:

 

10 SCREEN0,1

20 GOTO20

RUN

 

?

 

..ciaran