Osborne 1 keyboard repair - success!

[Tom Hunter]

I have managed to completely disassemble the bad Osborne 1 keyboard -
remove all key mechanisms (body, plunger, main spring and actuator spring),
remove the 3 layer membrane from the aluminium backing board and separate
all three membrane layers (bottom, spacer and top) - all without damaging
or losing any bits.
I then carefully cleaned off all adhesive and other sticky gunk from all
layers using various solvents including water, isopropyl alcohol and white
spirit.
The silver tracks remained undamaged as confirmed with a multimeter.
I then carefully reassembled the 3 layers, inserted and super-glued the
keyboard mechanisms in batches, testing after each batch.
I did not use any glue to reattach the 3 membrane layers so they are held
together only by the keyboard mechanisms with their prongs protruding
through the layers into the aluminium backing plate to which the prongs are
super-glued.
I sealed the edges around the membrane using Kapton tape to provide
protection from dust etc. The tape also attaches the membrane edges to the
aluminium backing plate.
All keys except the "Alpha Lock" key work perfectly. It appears that I have
damaged the address line 7 on the bottom membrane. I can live without
"Alpha Lock" so I did not pull everything apart again to fix this
un-important key.
The conclusion is that membrane keyboards can be fixed if your life depends
on it. It is absolutely uneconomic though. I worked about 30 - 40 hours on
the keyboard alone. Working Osborne 1s sell for between US$100 and US$300
on Ebay.

Regards
Tom Hunter