[Coco] 512 Upgrade

[Carey Eugene]

This may not help you, but way back when I did my 512k upgrade I too had 
problems.

I don't remember the exact details, but it went something like this...

I followed directions...

I clipped the caps.  I put the new memory chips in.  I installed the board.

It partially worked.  I think somewhat like yours, but I'm not sure.

I paniced.

I jumpered the caps back and installed the old memory chips.  It worked, 
resulting in partial relief.

Reinstalled the 512k, it failed.  I checked the chips to make sure they were 
fast enough.  I swapped chips around in case I had gotten a bad one.  Didn't 
help.

I tried it again but this time left the jumpers in, and it partially worked. 
It seemed to work, but I wanted to make sure, so I ran some memory 
diagnostics and it would occasionally fail.

During my testing, for some reason I used an aligator clip to jumper the 
caps, and it started working completely.  Passed the diags, burn in testing, 
all of it.

I put in some wire wrap wire to permanently jumper it and it failed.

I put the aligator clip back in, and it worked reliably again.

So I left the aligator clip jumper in it and soldered it solid and it worked 
reliably ever since.

I ran heavy diagnostics on it for days and it worked fine.  I used it for 
many years and it worked fine.  So what I did worked.  I don't know why, 
though.

I'm certainly not too bright when it comes to hardware, but I'm guessing 
that I probably shouldn't have clipped the caps, even though the directions 
said to do so.  And possibly some quirk in the chips or the CC3 just needed 
some extra capacitence or something that the aligator clip provided.


I don't know if that helps, but I thought I'd mention it.

Wish I could remember more details, but that was 15+ years ago.

Carey




----- Original Message ----- 
From: "Rick Ross" <rickross at mail.rossprogramming.com>
To: <coco at maltedmedia.com>
Sent: Tuesday, August 08, 2006 11:22 AM
Subject: [Coco] 512 Upgrade


Anyone who could help me I would be grateful :-)



I have had a new Tandy 512 upgrade lying around and a perfectly good cc3
with 128k. so I figured why not make a 512 that doesn't work!



I removed the existing chips and snipped c65 and c66 dropped the new 512
in....



Turn it on and get green with no text. Removed 512 and put the old chips
in - same thing a green with no text.



I am quite sure this has been seen before, if so can you give me a clue?



Thanks!

Rick






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