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

[Tim Fadden]

I have seen similar symptoms with loose memory chip contacts, and gime 
contacts.  Even though the machine is new, 25 years new! ha ha ha  I 
would re seat all of the socked chips, and to an eraser job on the 
motherboard rom-pak contacts.

Tim

Brian Sturk wrote:
> Robert Gault wrote:
>> 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.
>>
>> -- 
>> Coco mailing list
>> Coco at maltedmedia.com
>> http://five.pairlist.net/mailman/listinfo/coco
> Hi there,
>
> Sorry for not being more specific.  I'm using the composite video out 
> to a 1702 monitor.  I'll try a better cable, good idea.  The 
> interference only seems to happen when the cart port is being used and 
> after.  If I just boot up the coco w/ something plugged in it stays 
> fine.  And it seems like something bad coming out of the coco.
> Interference from a magnetic field has a certain look and this seems 
> more like something else.  On a black screen I can see hints of orange 
> and blue.  It's almost like random repainting of the screen *and* the 
> magnetic field effect.  Definitely weird.
>
> thanks for the help, I'll report back,
> ~telengard
>