Re: restoring electrical conductivity of PET keyboard pad tips

From: Ethan Dicks <ethan.dicks_at_gmail.com>
Date: Fri, 3 Nov 2017 16:21:23 -0400
Message-ID: <CAALmimkgctOF390w2kPuqZV3_-3OoVk0BXHg7KYVXH5n5DVWWg@mail.gmail.com>
On Fri, Nov 3, 2017 at 3:42 PM, william degnan <billdegnan@gmail.com> wrote:
> Here is what I have so far
> http://vintagecomputer.net/browse_thread.cfm?id=703
>
> (waiting on the Keypad-Fix to be delivered via 2-day delivery)
> https://www.amazon.com/gp/product/B0026PRMVM

Thus far, all of my alcohol cleanings have been effective and I
haven't resorted to paint or other add-ons, but if you are going to
experiment, let me recommend measuring the resistance across one or
two keys, then clean with alcohol, check again, then try the
keypad-fix or any other refurbishment techniques and measure the
resistance every time.  I found while restoring a TRS-80 Model 4 kb
that working keys started off around 400-600 ohms, bad keys were 2K
ohms or more, then after successful cleaning were more like 100-200
Ohms.  Unsuccessful cleanings did happen, but in the case of the
TRS-80 keyboard, I found that rotating the rubber pad 90 degrees put a
different part of the rubber in contact with the terminals in the
keyswitch and then those same switches went from 2K down to under 300
ohms.  I don't know that doing this for Commodore keys will work
because I think more of the pad touches the fingers compared to the
TRS-80 design, so there might not be enough unglazed rubber to rotate
into use there, but it's an easy test.

-ethan

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Received on 2017-11-03 21:00:05

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