[Coco] need help repairing a coco 2

[Retro Canada]

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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