Re: Apple II+ keyboard weirdness (help with repair)

[Roger Johnstone <rojaws@es.co.nz>]

In <SI1qa.35507$MZ6.32035@fe05.atl2.webusenet.com> Rob Diehl wrote:
> I got out our family's old Apple II+ computer after 10 or so years of
> sitting in the closet. My dad loaned it out to a family with some kids 
> and ever since then the keyboard stopped working. Well, that was a 
> long time ago and I am on a mission to repair it. Everything in the 
> computer works great except for the keyboard which gives absolutely no 
> input to the computer under any circumstances except for the reset 
> button (which doesn't really count I don't think, since it is somewhat 
> isolated from what I recall after reading the Apple II Redbook).
>
> The Apple II Redbook helped me diagnose the machine somewhat, but 
> lacks detailed pin descriptions of the keyboard controller board 
> itself, and only gives the pinout of the socket that connects to the 
> motherboard via ribbon cable.

..

> My wild guess right now is the Keyboard Controller IC is fried, but 
> that doesn't really explain the strange signals on the 7400 or 7404. I 
> made sure the chip was socketed properly by checking each pin for 
> continuity, and it's fine as far as that goes. Nothing seems 
> discolored or anything, the board actually looks to be in really good 
> shape other than the keyboard simply does nothing.
>
> I have a few of questions:
> 
> 1) What do you think is wrong?

I don't know. Don't forget though that the keyboard encoder scans the 
key matrix, so many of the pins will be rapidly toggling between their 
high and low states. On a meter this may look like a strange voltage. 
You really need a logic analyser, or at least a simple logic probe to 
tell what's really going on.

> 2) Where can I get a detailed pin description of the keyboard 
> controller board? The Apple II Redbook seems to have everything 
> covered in great detail except for the keyboard.

This I can help with :-) I have a copy of the later Apple II Reference 
Manual which covers the Apple II and II+. It has the keyboard encoder 
circuit in it, which I have scanned and uploaded to <http://homepages.
ihug.co.nz/
~rojaws/Apple II keyboard.tiff.gz>

> Any other advice (other than to trash it) is appreciated.
> 
> Thanks
> 
> -Rob

-- 
Roger Johnstone, Invercargill, New Zealand

Apple II - FutureCop:LAPD - iMac Game Wizard
http://homepages.ihug.co.nz/~rojaws/
________________________________________________________________________

"All parts should go together without forcing. You must remember that
the parts you are reassembling were disassembled by you. Therefore, if
you can't get them together again, there must be a reason. By all means,
do not use a hammer."  
                           IBM maintenance manual, 1925