Re: Dead keyboard!

["Michael J. Mahon" <mjmahon@aol.com>]

Tristan Mumford wrote:
> Hello,
>
> As you may have seen I just succeeded in resurrecting my clone.
> It has one remaining issue. The keyboard doesn't work.
> Well, to be more precise the LED button (control?) + Reset button combo
> still works fine, and the LED on aforementioned button stays lit merrily,
> but nothing else works.
> What's wrong with it?

Those keys both switch low impedance circuits (the reset line), and have
a dedicated wire in the keyboard cable.

The matrix keys are polled by an encoder with relatively high impedance
inputs.  You may want to check the keyboard PC board for corrosion or
leakage paths, as well as some of the keyswitches.

And, since *no* keys seem to work, the cable to the encoder board,
the connectors, and the encoder itself are all suspect.  In fact,
until you get *something* into the keyboard port, even the keyboard
multiplexer on the main board cannot be trusted.

Since the keyboard is a popular place for ESD entry, it's hard to
rule out any failure offhand.

-michael

NadaPong: Network game demo for Apple II computers!
Home page:  http://members.aol.com/MJMahon/

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