[Coco] Broken CC3

[George Ramsower]

----- Original Message ----- 
From: "Bruce W. Calkins" <brucewcalkins at charter.net>
To: "CoCoList for Color Computer Enthusiasts" <coco at maltedmedia.com>
Sent: Monday, September 15, 2008 6:44 PM
Subject: Re: [Coco] Broken CC3


>> Well, I'm stumped.
>> I found the power supply was clean after all, I think.
>> AC noise on the 5V line is < 20mv. However, I'm seeing that noise on the 
>> ground also. So I suppose this is just noise on the power line to the 
>> scope.


> Ground Loop?

 I suppose that's what it is. I don't have an isolation transformer to prove 
this. My GOOD O-Scope(B&K) has a bad cap in it somewhere and I would love to 
use it. The one I'm using is a TV scope. It was FREE and I use it when 
needed.
Maybe I should get that B&K out, warm it up for a few hours and see if it 
will still work. I love that thing.
It would take about an hour for it to work correctly in the past. I wish I 
had a service manual on it.

>
>> Is it possible the ROM in the coco could have failed?

> That is a long shot.  The original is a masked ROM.  Basically, you would 
> have to kill it outright.
>
> Bruce W.

 I thought this might be the case. I don't know much about "Masked ROMs" but 
I was thinking that, what if there's something that caused a bit or byte to 
change and may cause this problem.

 I don't know everything and I am just guessing at this point.