Remember that crummy Atari 130XE I cleaned up a while ago and how nice turned out? I have been playing around with it for the last couple of days when Murphy struck - the whole block of function keys (Help Start Select Option Reset) suddenly stopped working. I noticed something was wrong when most games failed to boot out of the blue, didn't take long to find out it was due to holding Option to disable the built-in BASIC not working anymore because of dead keys. Checked continuity on the membrane tracks and sure enough several of them went open circuit near the edge connector, corresponding to the block of keys I lost.
My usual method of going over the tracks with ordinary pencil lead didn't lower the resistance enough (several kΩ) and carefully taped strips of aluminum foil didn't make enough contact to get it working, some sort of conductive paint seems to be the only option. Went to a bunch of auto parts stores looking for a rear defogger repair kit containing said paint, but nobody seems to bother stocking it anymore. Argh!
Today I finally found something called Electric Paint at an expensive electronics store near me so I bought a tube and had a go at the keyboard membrane:
I have to say I'm not very impressed with the stuff. Looks and feels like Arctic Silver 5 without the stickiness, doesn't adhere very well to plastic (it won't survive more than one insertion cycle) resistance is quite high even when applying loads of it (400+Ω for short segments) and the package warns of a 6 month shelf life. But it conducts well enough to get the Atari to recognize the dead keys back. Yay!
Now let's see if it lasts... 😵
Also good to see them CRTs getting some love!