Osborne 1 keyboard repair?

[Jules Richardson]

On 9/21/20 6:41 AM, Tom Hunter via cctalk wrote:
> I cleaned the now exposed membrane using Isopropyl alcohol - no change in
> resistance.

I don't think you've really exposed anything, have you? The membrane is 
going to be three layers - a bottom layer with traces on the upper side, a 
spacer layer, then the top layer with traces on the underside; you're 
looking at the top of the membrane from the "outside".

I expect it's all heat-staked together, but it might be possible to 
dismantle, separate the layers, clean the conductive surfaces and the 
spacer, then reassemble.

My guess is that what happens is either:

a) repeated keypresses over time result in some conductive material wearing 
off and depositing itself on the spacer, eventually bridging the gap and 
registering as a short/press.

b) corrosion of the conductive surfaces results in the same thing.

Either way, cleaning would likely fix it - but only if the membrane comes 
apart; it may well be sealed together at the edges.

Alternately you might, I suppose, be able to drill a small hole through the 
membrane close to the problem area and inject some cleaning solution 
between the layers that way, but I don't know how successful that would be.

cheers

Jules