[Coco] need help repairing a coco 2

[Luis Antoniosi (CoCoDemus)]

yes, the 6847 is already wired to produce text video, in fact you cannot
turn it off.

and yes, i had one 6809 with 2 pins blown.

Luis Felipe Antoniosi



On Thu, Oct 16, 2014 at 3:02 AM, Didier Derny <didier at aida.org> wrote:

>
> the 6847 can produce the "beginning" of an image without being programmed ?
>
> the 6809 can be only partly blown ?
>
> thanks
>
> --
> didier
>
>
> On 16/10/2014 00:25, Retro Canada wrote:
>
>> its pretty easy through a mialigned cartridge to blow the 6809. you coul
>> blow it entirely or some pins. this is the first thing to replace. the
>> second is the ram chips. the you go for sam and pias.
>>
>> the 6847 is working fine
>>
>> On Oct 15, 2014, at 6:14 PM, "didier derny" <didier at aida.org> wrote:
>>
>> I have a coco 2 with no video on tv output.
>>
>>
>>
>> I built the composite interface on a breadboard
>>
>> Obviously I'm getting an image.
>>
>>
>>
>> But the machine is not correctly starting
>>
>>
>>
>> When I start or reset the machine I get
>>
>> The following patterns:
>>
>>
>>
>> 1/ Orange screen
>>
>>
>>
>> 2/ mix of green/orange lines not correctly synchronized
>> http://netfilters.eu/p2.JPG
>>
>>
>>
>> 3/ black screen with random green square containing the letter 'P'
>> http://netfilters.eu/p3.JPG
>>
>>
>>
>> 4/ mixed pattern, orange bands with green square containing the letter 'P'
>> http://netfilters.eu/p1.JPG
>>
>>
>>
>> I removed all the component on socket and clean the pins.
>>
>>
>>
>> If I remove   ram or sams or  eprom I don't get any image
>>
>> So my "theory" is that the 6809 starts
>>
>>
>>
>> The coco 2 is a 16k Korean one with 2 small sockets beside the ram chips
>>
>>
>>
>> Any idea ? it's the first time I repair a coco
>>
>>
>>
>> Thanks
>>
>>
>>
>> --
>>
>> Didier
>>
>>
>>
>>
>>
>>
>>
>
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