Re: Notes on Cleaning and Repairing an Apple II Plus

[Linards Ticmanis <ticmanis@gmx.de>]

On 04/25/2011 11:22 PM, Michael J. Mahon wrote:

> Once you spray or wash something into a keyswitch, any non-volatile
> components (including dissolved dirt) will stay there forever--unless
> you enjoy disassembling keyswitches and manually cleaning them.  ;-)

Which isn't all that hard with the black-and-gray switch type Apple or
their keyboard supplier seem to have used most commonly. Just unsolder
the problematic switch, remove the caps of the surrounding keys, press
the snap-in thingies towards the center and carefully pull it out
(upwards). Then it's easy to take it apart, it's all just snapped
together, no screws, no glues. As long as you remember where each part
goes and take care that the spring doesn't propel itself away, you can
then get a small screwdriver or something similar between the two actual
contacts and carefully scratch a bit, then reverse the whole process.
That way I recently revived some switches which simply weren't willing
to work right - I'd get either no character on screen or several at
once, no matter how many hundreds of times I had pressed the key. Turns
out the culprit was a bit of verdigris which had formed on the contacts,
probably too much of it to be removed without disassembly.

> It is definitely pre-rev 7.  You can either use the proto area in the
> lower right corner of the board (slots on top) to wire up the enhanced
> color burst gating that was pre-installed on the rev 7 board, or you
> can try a different color monitor, hoping for one that is less sensitive
> to color burst leakage.

Actually the reliable interim fix didn't happen until Rev. 8 or 9
according to Jim Sather, and the final fix came with the RFI board. I
had to do the fix on my Rev. 7 board to get it to play with a particular
TV set, putting in an extra 74LS04 if I remember correctly. Which I then
also used to get rid of the infamous "orange line" at the left edge of
the screen.

-- 
Linards Ticmanis