Kim / Commie keypads

Not only is it a matrix, but it appears that the matrix scan connections are available at the expansion connector. 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 particular