Recurrent Keyboard Failure on GE clock radio

My favorite old GE clock radio has metal membrane
keys for the direct-set alarm.
Looks like this:
http://nm7u.tripod.com/homepage/keys.jpg

Every six months or so, they quit working.
Starts at the bottom row and works it's way up
over a period of months.
I take it apart and run a strip of paper soaked
in alcohol between
the contacts and it's all good for another six months.

I'm wearing out the screw holes that mount it together.

Is there anything I can put on the contacts to retard
oxidation or whatever's happening?
I thought it was dirt, but sealing the whole thing in
packing tape didn't help a bit.

The radio isn't worth nothin' but it sure is easy to set
the alarm time...when the keys work. I have two of these and
they both have the same problem.

Ideas?
mike
--
Bunch of stuff For Sale and Wanted at the link below.
laptops and parts Test Equipment
4in/400Wout ham linear amp.
Honda CB-125S
400cc Dirt Bike 2003 miles $550
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http://www.geocities.com/SiliconValley/Monitor/4710/