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Macintosh Plus Keyboard Issue

R

RHopple

Experienced Member
Joined
Nov 30, 2017
Messages
55
I recently picked up a good looking Mac Plus from eBay, with 2.5MB of RAM, external floppy drive, and keyboard and mouse. The system works great and boots to System 6.0.7, but the keyboard has an issue. Specifically the 'm', ';', 'q', and 'p' keys sometimes do not work. The latter two never work with the others sporadically working. I have cleaned the keyboard with compressed air and contact cleaner, but the switches don't seem to be making good contact. Another thing to mention is the internal floppy drive: it makes a loud whirring sound when reading and writing but functions fine. I have seen videos of how the drive should sound, and mine is much louder. I'm just glad it works! :) Any suggestions for the keyboard?
 
You can have a try and remove not working keys.

Those are soldered and hold to the board by two plastic clips, keys can then cleaned on the inside (take care when opening the two halves, the spring can be lost)

800k drives are notorious for thick grease...
 
Most definitely, the problem with the keyboard are the switches themselves. I just checked my schematic for the keyboard, and all the keys you mentioned are on separate paths to the encoder chip, so no chance it is the encoder chip.

Your particular keyboard has either the SMK, Mitsui or Alps switches.

SMK: https://deskthority.net/wiki/SMK_J-M0404_series

Mitsui: https://deskthority.net/wiki/Mitsumi_standard_mechanical_lock

Alps: https://deskthority.net/wiki/Alps_SKCC_Tall_Cream

Look at all of the links above, and see what switches your keyboard use. At least with the Alps and SMK switches, they're easy to find on eBay. Just takes desoldering, and pulling the switch out of the metal frame.
 
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