Author Topic: Need help identifying CPlus/4 switch type.  (Read 611 times)

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Offline Pretendo

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Need help identifying CPlus/4 switch type.
« on: Sun, 25 September 2011, 15:47:25 »
Pulled the keyboard out of a Commodore Plus/4.  This was the unpopular cousin of the C64, meant to compete with base line ($100) PC models around 1984.  It was a flop in the states, but apparently had some popularity when the unsold units were dumped on western Europe for considerably slashed prices.

This is the keyboard (center).
http://geekhack.org/attachment.php?attachmentid=27289&d=1316981494

Keys are double shot like most of this era.  The frontal text is screen printed on.  Arrow / function keys use rubber dome.

Having trouble classifying the regular key switches.  Here's a detail of one, plus the under side of a key.  The spring usually sits inside the switch housing, with the small end fitted into the key.

http://geekhack.org/attachment.php?attachmentid=27290&d=1316981554

As you can see, the switch consists of a spring, widened at one end, the keytop, a gold contact and a strip of rubber padded with graphite laying over top the contact.  When the key is pressed down, the spring pushes the coated rubber over the contact, completing the connection.  It seems like a relatively stupid way to design a switch. The rubber would wear out relatively quickly with use.  Keyfeel also sucks.  More and more force is required to push the key as it gets lower.

All besides the point, though.  Does anybody know the type of switch this would qualify as?
IBM Model F-122 6110347 -- September 13th, 1984
IBM Model M 1391404 -- April 14th, 1988
Rosewill RK-9000

Offline HairyTroll

  • Posts: 26
Need help identifying CPlus/4 switch type.
« Reply #1 on: Mon, 26 September 2011, 12:09:49 »
You may want to post this question to the cbm-hackers mailing list.

http://www.paradroid.net/cbm-hackers.html

Bil Herd was the principal engineer for the Plus/4 and he is active on that list.

Offline Pretendo

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  • Posts: 113
Need help identifying CPlus/4 switch type.
« Reply #2 on: Tue, 27 September 2011, 12:38:35 »
Haha, will do!

In its defense, I think it was pretty well made for the price point of the machine.  IBM Pc jr. had that ever popular chiclet keyboard; they weren't the only ones to use it either. The cheaper version of the Plus/4 (C116) had chiclets.   The Atari 400 had those membrane switches, like on a microwave, which was reason enough to upgrade to the 800!

At least the Plus/4 had full travel keys with some sort of resistance!  The board had a steel back plate too, which weighed more than the rest of the computer parts combined.
IBM Model F-122 6110347 -- September 13th, 1984
IBM Model M 1391404 -- April 14th, 1988
Rosewill RK-9000