[Coco] Re: [Color Computer] CoCo 2 questions.

[Mike Pepe]

Phill Harvey-Smith wrote:
> Glen VanDenBiggelaar wrote:
> 
>>Hi, Phill,
>>What Model number is it?
> 
> 
> 26-3136A It is a UK PAL version tho.
> 

I have a scan of that schematic. It's pretty hefty at 9MB...

>>I have the service manual the 3026,3027. Upgrade instructions are on my 
>>website (www.coco.8bit-micro.com) on the CoCo 2 page. yes, You want to 
>>replace the chips with 4164 with 200 NS or better time (a good example is 
>>TMM4164AP-20 ). I will look closer at the scematics for the other chips you 
>>mentioned.

It's a little different, Glen

> 
> So looks like upgrade is indeed 2x41464, doesn't work at the moment, so 
> if you (or anyon else) have a circuit for this model would be most 
> greatfull.

The official upgrade is 8x64kx1, but you can do 2x64kx4 if you want.

> Fault is vertical lines of @ down the screen, I suspect a data path 
> fault, ie one of the LS chips that sits between Ram and VDG and RAM and 
> CPU.

If you pulled the 785 and popped it in the dragon, it's not that then.

I'd guess dead 6809. If the video chip is dead that's going to be hard 
to find, it should be a 6847T1 in there. (not compatible with the normal 
6847)

the A model, by the way, is a 16k extended basic. The B version is 64k.





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