[Coco] Weird CoCo3 problem...

[Brian Blake]

Hi Art,

Yes, I did check the continuity tonight after I did the latest checks - <1 ohm from the Coo's IC9 pin 9 to IC8 pin 15 on the controller.


----- Original Message ----
From: Arthur Flexser <flexser at fiu.edu>
To: CoCoList for Color Computer Enthusiasts <coco at maltedmedia.com>
Sent: Tue, January 5, 2010 9:37:12 PM
Subject: Re: [Coco] Weird CoCo3 problem...

This may be a little simple-minded compared to analyzing waveforms,
but have you checked the resistance (continuity) between something
that connects to the SCS pad of the disk controller edge connector and
something that connects to the same pad of the CoCo's cartridge
connector, in line with Mike's final paragraph?  That is, plug the
disk controller in with its cover removed to the CoCo with its cover
removed and check continuity along the SCS path (with power off).

Art

On Tue, Jan 5, 2010 at 8:10 PM, Brian Blake <random_rodder at yahoo.com> wrote:
> Okay, I spent some time cleaning the probe and other things this evening. I'm happy to say that made an improvement in the waveforms - all waveforms between the two systems are almost identical.
>
> The one are I have concern is the /SCS:
>
> On the CoCo3 in which the FD-502 does work on, that is in the neighborhood of 4.25v with the blips Mike was talking about.
>
> On the 'Bad CoCo' there is a constant 2.24vdc with no discernible blips.
>
> Any other areas to check in order to confirm this?
>
>