Original "phone jack" keyboard, keys work intermittently

[sambapati87]

Hey guys,

Just acquired what appears to be a pretty solid Mac Plus from craigslist. Boots from floppy fine (phew—my other Plus's floppy drive refuses to cooperate), very strong video/analog board, etc.

However, the one keyboard I have for these seems to have certain keys that work never, and certain keys that work intermittently. I remember trying to fix this a while back by taking the keyboard apart and cleaning it, but it didn't work. Does anyone have any specific ideas on ways I can repair this? I'd rather not look to eBay to replace it.

Thanks!

 

[mcdermd]

Push down REALLY HARD and rock it back and forth, up and down. If that does not work, take the keycap off, put a drop of isopropyl alcohol on the plunger and work it up and down, pushing to all four sides slightly.

 

[James1095]

And if that doesn't work, desolder and remove the offending keyswitch, take it apart and clean it out. This is a fairly common occurrence on these.

 

[cb88]

I have the same issue on the Plus I got from mcdermd. The a key doesn't really work at all and various letters get stuck repeating... so I may need to replace the few caps on the board. Looks like someone was prying at the a key as there are scratches on the metal around there LOL. A keyboard like this on ebay goes for more than the shipping I paied from mcdrmd! so ... definitely going to try to repair it.

Wiggling it, alcohol etc didn't help... I also cleaned the back of the board with soap and toothbrush.

I guess I may as well break down and get a solder station...

 

[James1095]

I haven't had any luck with external means. The only thing that worked for me was to desolder the defective switches, take them apart, and manually clean out the insides then put them back together. It's a bit fiddly but once you do it a few times you can do it pretty quickly.

 

[techknight]

Are these vulnerable to the contact plating tarnishing over time? If this is the case then thats the likely cause of failure.

I seen this ALOT with vintage stereo equipment, the slider switches and rotator switches do this. Even dating as late as the 80s, and as early as the 40s/50s of course...

 

[James1095]

I've seen some that just had a bunch of dust in them, and others various unidentifiable goo that had crept down between the contact plates. Once you get it apart, a wipe down with DeOxit and reassembly usually works.

 

[macclassic]

I repaired my Plus keyboard about six yers ago, and made a toool to pull the keys off and two metal strips to ease the switch out when de-soldering the pins.

After dissembling the switch, I inserted a small piece of cardboard (coloured purple in the second photo) between the switch board and the switch body as I found this makes them work again.

The switches stop working due to a physical lack of contact at the point shown in the third photo.