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
