[Coco] [HW] Coco 3 video output corrupt when using cart port

[Robert Gault]

Brian Sturk wrote:
> Hi there,
> 
> I have a very good condition Coco 3 (bought sealed new, used a few 
> times) and I just recently started using the cart port/bus.  I've used 
> cartridge games and the SVD virtual disk drive device and when using 
> them the video output gets very garbly.  Any ideas on what it might be?  
> At first I thought it was the SVD but it happens with the games also.
> 
> Hopefully a kind coco hw guru will have some ideas.   :) I'm going to go 
> poke around looking for schematics and a way to search the mailing list 
> archives.
> 
> thanks,
> ~telengard
> 

Which video output do you mean? There are three video outputs on a 
Coco3, RF (red RCA jack), Video (white RCA jack), and RGB (9-pin on the 
bottom of the case.

For any of these, the quality of the cable (poor shielding) might be a 
problem. If using the RF jack, make sure the slide switch (CH) is 
selecting an unused channel in your area. For the composite or RGB, I 
can't think of any reason why a cartridge should interfere with the 
video signal.