[Coco] Caring for a CoCo

[Mark Marlette]

Jim,

Might want to check to see how long the interface leads of the 512k are.

I have seen ones that are too long and allow the 512k board to bottom out on the motherboard, cause shorts.

There are traces that run under the CoCo's 512k expansion connectors and  the connectors DO NOT have a physical bottom or stop to them. Dumb, cheap, what ever you want to call it.

I suspecting that your homemade version is a wire wrapped model or is it a PWB board? Depending on signal routing and crosstalk of other w/w wires, this will cause this erratic operation to occur.

Mark
Cloud-9


----- Original Message -----
From: "Jim Hathaway" <kg4knb at hat3.net>
To: "CoCoList for Color Computer Enthusiasts" <coco at maltedmedia.com>
Sent: Thursday, November 19, 2009 9:15:32 AM GMT -06:00 US/Canada Central
Subject: Re: [Coco] Caring for a CoCo

On Thu, Nov 19, 2009 at 8:27 AM, Mark Marlette <mmarlette at frontiernet.net>wrote:

>
> Since the machine is apart. I would remove the GIME, with the proper
> tooling, a PLCC chip removal tool, and clean the leads. Soft white eraser,
> rubbed in the direction of the lead. This will ensure that you don't bend
> the lead.
>
> Materials tarnish, sockets are a HUGH reliability factor. In defense
> designs, we can't use them, nor want to for this reason.
>
> Not sure if you are using a multi-pak or not. Same applies here. Tandy did
> not use gold on their card edge connectors in the multi-paks or in the
> floppy controllers, 502 might have. My dev. system runs 24/7. Failure points
> will be in the multi-pak OR cards that DO NOT have a gold card edge. Another
> reason why ALL Cloud-9 products, that have a card edge connection, require
> that surface to be plated with gold. Thus a higher cost, but higher
> reliability = quality product.To clean the card edge connections, again use
> the white soft eraser, it won't be white for long....... :)
>
> Mark
> Cloud-9
>
>
>
Thanks for providing some more details around possible failure points.  I
have been dealing with issues from my two CoCo 3 systems in the past year or
so.  The first issue was the complete failure of a 512k memory board.  This
one drove me crazy and I spent lots of time replacing all the memory chips,
replacing caps on the board and also trying to re-flow the solder
connections on the board.  All of these steps did not help, and so in the
end there is something else that has caused this board to fail.  This board
was manufactured by Performance Peripherals.

My only working 512k board that is 'working' is a home made 512k simm board.
 However when I use this board in either of my systems and attempt to use
drivewire and boot into nitros I find that after a few minutes the system
becomes unreliable, locking up, weird characters on the screen, etc.  I
suspect the simms might be bad, but have not done extensive testing.

At this point I am not even connecting my multi-pack to my system(s) because
as you stated this is just another point of failure (all the connections).
 I figure I should be able to take just a stand alone 512k CoCo 3 boot into
nitros via drivewire and have a reliable system.

Jim





> ----- Original Message -----
> From: "Boisy G. Pitre" <boisy at tee-boy.com>
> To: "CoCoList for Color Computer Enthusiasts" <coco at maltedmedia.com>
> Sent: Wednesday, November 18, 2009 6:00:45 PM GMT -06:00 US/Canada Central
> Subject: Re: [Coco] Caring for a CoCo
>
> I would think that would be an issue with a lot of CoCos and might explain
> some of the "strangeness" that CoCo's exhibit as they get older.
>
> What would be the symptoms of this type of degradation james?
> --
> Boisy G. Pitre
> http://www.tee-boy.com/
>
> On Nov 18, 2009, at 5:19 PM, jdaggett at gate.net wrote:
>
> > On 18 Nov 2009 at 13:23, Mike Pepe wrote:
> >
> >> I would also consider changing out the electrolytic filter caps in the
> >> power supply, as they do tend to dry out with age and the increasing
> >> amounts of AC ripple riding through the supply can't be good for it.
> >
> > The electrolytics would only be a problem if the unit has sat for several
> years and not been
> > powered up. Yes the electrolytic materail tends to deform with age and no
> charge on the cap.
> > What happens then is the ESR of the cap goes way up. This reduces its
> function as a filter
> > against ripple.
> >
> > james
> >
> > --
> > Coco mailing list
> > Coco at maltedmedia.com
> > http://five.pairlist.net/mailman/listinfo/coco
>
>
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>
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