----- Original Message -----
From: Richard Erlacher <edick_at_idcomm.com>
To: <classiccmp_at_classiccmp.org>
Sent: Tuesday, April 10, 2001 2:07 PM
Subject: Re: Kim / Commie keypads
> Not only is it a matrix, but it appears that the matrix scan connections
are
> available at the expansion connector.
They are. I've tested the "broken" keys this way,
and they're all functional. (*Whew!*) :-)
Because the KIM uses a pair of 6530s, which are
nigh impossible to find anywhere at any price,
and there are two different flavors of them out
there that are not interchangable, this is good news.
In fact, 'till I read your message
the thought that it might not be the keypad had never
(*SHUDDER*) even entered my mind.
I could see mounting the whole KIM-1 unit in a box
with a lucite or red-filter cut-out for the 7-segment
display and a keypad near-flush with the top above
the "real" keypad. That would have the advantage of
being a place to put the filtered power source and
protect the unit from dust and further wear and tear
until/if ever a replacement keypad is found.
But still I would like a "nice looking"
keypad, or at least "not amateurish".
So does anyone know where one might find
a "take a bunch of keycaps and fit into a plastic
grid to make your own keypad array" sort of kit?
Membrane vs. standard, 5x4, 4x6, whatever,
as long as you can manually wire them into
the required 3x7 array?
:)
-- Ross
> It should be quite straightforward to
> deterine whether there's a faulty/inermittent connection and to isolate
it.
> It's just a matter of the associated tedium. That was why I suggested
that the
> on-board keypad could be replaced with an off-board one connected in a
similar
> fashion to the applicaton connector. That will "buy time" to find a
suitable
> replacement, and it will provide a replacement to use in the meantime,
also
> allowing the owner to regain confidence in the remaining functions on the
board.
> Moreover, it allows for the possiblility that there's a problem with the
board
> itself, i.e. intermittent trace, etc. If the external keypad connected to
the
> expansion connector doesn't work consistently either, it suggests there's
a
> problem with the board itself. Likewise, if the problem presently on the
board
> doesn't go away when wires are soldered in parallel with the existing
> matrix-scanner device connections, presumably a PIA or VIA, then it's
likely
> that the device itself may have been damaged, though I have a bit of
trouble
> imagining a circumstance that it would become intermittent if its solder
> connections are sound.
>
> What's most likely, however, is that the connections or traces have been
damaged
> over years of pressing on the keypad and thereby flexing the board. The
simple
> way to get around that is to solder on the fewer than two-dozen wires used
to
> hook up the keypad and expansion connector, and proceed from there.
>
> Ideally, one would generate a test routine for the KIM that would echo via
a
> parallel port, say, the value associated with the scan of the keypad.
This
> would be monitored by an external PC. That same PC would drive a matrix
of SPST
> relays wired in the same matrix as the keypad and attached, in one
instance to
> the physical switch connections on the underside of the KIM-1's keypad,
and in
> another at the expansion connector.
>
> After running it over a long time, e.g. a day or weekend, and logging, in
the
> PC, the time and date of each failure, one could then proceed to perturb
the
> circuit board, i.e. push on the keypad to see if it causes the externally
> generated switch closures to be misread or missed entirely. If the board
works
> perfectly when stimulated externally over a long period of time, and if it
> doesn't fail when perturbed, it's likely one or more of the switches is
worn
> out. That's when a different keypad becomes attractive. The KIM-1 Keypad
was
> never a thing of beauty or of any technical appeal. for purposes of
preserving
> the device, I'd say it's best to look for an exact replacement, in
whatever form
> it has to be obtained, and use an external keypad attached to the
expansion
> connector in order to retain use of the KIM-1.
>
> Dick
> ----- Original Message -----
> From: "Ethan Dicks" <ethan_dicks_at_yahoo.com>
> To: <classiccmp_at_classiccmp.org>
> Sent: Tuesday, April 10, 2001 2:21 PM
> Subject: Re: Kim / Commie keypads
>
>
> >
> > --- Richard Erlacher <edick_at_idcomm.com> wrote:
> > > It's pretty hard to tell whether it's the keypad or the circuit that's
> > > malfunctioning. How did you determine it's the keypad itself?
> >
> > Looking at the schematic, it appears to be a simple matrix. Short a
> particular
> > X and Y line for the questionable key. If it "strikes", it's the
keypad.
> > If it still flakes out, it could be a component or trace.
> >
> > -ethan
> >
> >
> > =====
> > Even though my old e-mail address is no longer going to
> > vanish, please note my new public address: erd_at_iname.com
> >
> > The original webpage address is still going away. The
> > permanent home is: http://penguincentral.com/
> >
> > See http://ohio.voyager.net/ for details.
> >
> > __________________________________________________
> > Do You Yahoo!?
> > Get email at your own domain with Yahoo! Mail.
> > http://personal.mail.yahoo.com/
> >
> >
>
Received on Wed Apr 11 2001 - 02:27:54 BST