Re: A2e not recognizing "N" and "S" keys--which chips to replace?

[mjmahon@aol.com (Michael J. Mahon)]

Jay wrote:

>Today, on a program's prompt to
>answer "Y" for Yes, "N" for No, I discovered that the "N" key did not register
>with the computer.  Went into BASIC and typed out the alphabet, and there it
>was again, and "S," too.

Not a chip, but the keyswitches.

I have found that pressing a non-functioning key a _lot_ (100-200 times)
will often clean its contacts enough to restore normal function.  This can
be observed if the computer is on and echoing keystrokes to the screen.

If that fails, the next step is to give the dirty switches a _little_ spray
of contact cleaner (available at Radio Shack, etc.) and immediately
(while still wet) repeat the "key exercise" part.

If that fails, try removing the keycap (carefully) and spray some more
cleaner directly at the junction between the shaft of the switch and
the body (to get more of it inside the switch), then repeat the standard
rat-a-tat-tat key drill.

The computer can be left on through all of this, so you can see any
progress on the screen.

If a key is still not functioning after all this exercise, then you may
be forced to replace the keyswitch (ugh!) or the whole keyboard (ugh!),
but those are definitely last resorts.

Here's the theory:  a switch is a simple component which is unlikely
to fail physically, but its contacts can become oxidized, preventing
it from closing a very low-current ("dry") electrical circuit.  Friction
from repeated use, perhaps with the assistance of contact cleaner,
will quite often remove the oxidation, restoring proper function without
having to do any harder work than pressing the key a lot.

As you might expect, "bad" keys show up more often on machines
left idle for a long time (no cleaning through usage) than on those
that are regularly used.

-michael

Check out parallel computing for 8-bit Apples on my
Home page:  http://members.aol.com/MJMahon/