10 Apr
2001
10 Apr
'01
7:27 p.m.
----- Original Message -----
From: Richard Erlacher <edick(a)idcomm.com>
To: <classiccmp(a)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(a)yahoo.com>
To: <classiccmp(a)classiccmp.org>
Sent: Tuesday, April 10, 2001 2:21 PM
Subject: Re: Kim / Commie keypads
keypad.
--- Richard Erlacher <edick(a)idcomm.com> wrote:
particular
> X and Y line for the questionable key. If it "strikes", it's the
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 If it still
flakes out, it could be a component or trace.
-ethan
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