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

[Brian Sturk]

Hi Tim,

I tried everything you suggested, still the same.  What's very 
interesting (and might help figuring this out?) is that it happens after 
a cold start but stops if I do a warm reset.  This was with a game 
cartridge.

~telengard
> 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
>>
>
>
> -- 
> Coco mailing list
> Coco at maltedmedia.com
> http://five.pairlist.net/mailman/listinfo/coco


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