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Need help with Keyboard issue on a Macintosh Plus Logic Board

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Hi Everybody, I really hope you can help me out!


I have a Logic Board and everything works fine, except the Keyboard. Once I plug in any working keyboard and open something where entering text is possible, it starts writing “aaaaaa...” endlessly. I really have no idea what the problem could be... however it's surely on the Logic Board, all other parts, especially the Analog Board work fine!


Thanks for any help!


Cheers, Michael

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Hi! It’s probably a stuck keyswitch on the keyboard that needs a cleaning? Some electronic cleaner might do the trick, but if that isn’t enough you might have to try disensamble the keyswitch and clean the inside. I haven’t tried this on a Plus keyboard but there might be instructions somewhere on the net.

There’s also a couple of caps inside the keyboard that might need to be replaced. @JDW has a nice video on the subject - I don’t remember if there’s instructions for cleaning in this video.

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Thanks, but that‘s not the issue. Tried it with 4 Keyboards which are all working fine on other Logic Boards.


It does differentiate though, if it‘s a broken keyboard. Then the board also doesn‘t write anything. 


Thanks a lot for trying to help me!




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Sorry - I missed the “any”... Besides checking the cable and the connector, I’m not much of a help further into the logicbard :-(

I hope someone more knowledgeable steps in and you’ll work it out!


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Thanks a lot either way. It‘s the same for me... I isolated the issue to the logic board itself but besides that I have no idea. I can only say for certain that it‘s not the keyboard / cable / or even the connector on the board.

Also that‘s a strange issue I couldn‘t find anywhere on the internet (or in the books)...

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