repair or replace ALPS key switch

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Joined: May 16 2021 - 08:07
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repair or replace ALPS key switch

The right arrow key on my //e finally became unusable.  It appears this is a long stem ALPS switch.  Taking it apart and digging online I find the way it works is when the plunger goes down, the pressure is redirected horizontally by a "leaf spring" which presses against a switch plate.  There is a tiny dimple in the center of the leaf spring which I suppose enhances the pressure.  Experimenting with an ohm-meter shows that the switch plate works fine if I remove the leaf spring and apply the pressure directly with a small screwdriver.  So I wondered if it might be worth trying to reshape the leaf spring with tweezers to get the pressure up.  Perhaps another option is to try and clean the contacts in the switch plate (how?).  On the other hand maybe all this is unlikely to work and it would be better to search for a replacement (not sure of the prospects?).

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Joined: Aug 4 2015 - 14:30
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Try Contact Cleaner

Try to spray a bit of contact cleaner down the stem so it goes into the contact. Then massage it by pressing it for a while. Let it rest a bit. Repeat if necessary.

I managed to revive a apple IIe keyboard this way. Many keys didn't work. By using contact cleaner they all began to work.

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Last seen: 2 weeks 3 days ago
Joined: Apr 26 2016 - 08:36
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Taking it apart and digging

Taking it apart and digging online I find the way it works is when the plunger goes down, the pressure is redirected horizontally by a "leaf spring" which presses against a switch plate.

 

Modifying the advice in the previous response, I suggest getting some of the contact cleaner into the leaf of the spring contact.

It might also help to pull a paper towel through it, being careful not to damage the separator insulator on the perimiter of the leaf-contact switch.

 

I think that you might find that it will work after that.  If not, try swapping the plastic stem with one from another key.

It's possible that the combination of worn stem and marginal contact is adding up to an unreliable keyswitch.  

 

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photos of disassembly

I found a seller on e-bay and requested 8, hope is I can get 1 of them to work with the contact cleaner as suggested.  As for the current one, I felt at liberty to mess with it.  I'm posting photos here for general interest and to see if we agree on how it works.  I'm claiming the leaf spring never makes any electrical contact, it only applies pressure to a deliberately "weakened" region of the plastic switch plate cover.  I identified where I think the pressure is applied in the photos.  This pressure then pushes the front conductor inside the switch plate toward the rear conductor; the two are separated by an insulator with a hole in the middle where the contact occurs.

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