orinoko wrote:jarreboum wrote:Turns out my dead clicky springy IBM keyboard wasn't so dead after all! After an extensive repainting of most of the membrane tracks, every contact were finally working. I took some time to clean all the keys and mount everything back, and while all keys are working ( I'm typing with it right now), some keys seem to have a faulty spring as they activate at the gentlest touch, not a normal keypress. Ugh, it means I'll have to open it again to change them. Removing keys and reseating them is only fun the first time, after the fourth time you just want to be done with it.
Please tell me your repaired a Model M2!! I tried to redraw the membrane traces using a liquid silver conductive pen but the resistance looked way too high and putting it all back together just to test it is a pain...
I did! some of the corroded traces were near the board and inaccessible without taking it out, which made me decide I would be better of buying one that works. Unforeseen expenses made me rethink that goal, and after a long struggle I managed to extract the board off its plastic cradle without breaking anything. I can see why people say they break easily though, everything is so tight you need to put a lot of force on the legs and breaking them is very likely. I think I was lucky on that one.
Working with silver ink is tedious. The conductivity goes up as the ink dries, and I found no difference in resistance over similar distances compared to the original traces. There were some instances where I had to scrub away the protective varnish, again very carefully as not to remove the underlying trace. The solvent of the silver ink dissolves the traces too, so it plays a role in the initial lack of conductivity. I found this out as I spilled some ink over the neighbouring traces (which would connect everything upon drying): when I wiped it out, I wiped the traces with it! Luckily they were all straight lines so I could redraw them easily. I waited 24h after each application before testing, as the smallest wet spot can prevent conductivity.
Finding the corroded part is key. It's often a small bit that spoils everything, and when that bit is under varnish, strategic scrubbing needs to be done to pinpoint the fault and repair it.
I also thoroughly cleaned the contacts on the board (it's a simple edge connector), and tested it by half-inserting it and holding it tight while pressing on the membrane with my finger. This was mainly to test if there was any short and if the inputs were somewhat reliable, though the unseated board can add to the errors. Using a dedicated keyboard testing software helps a lot.
I did break some of the plastic legs holding the keyboard together though, which made me experiment with new ways of gluing plastics. I had bad experience with traditional super glue on plastics, so I used tough but elastic super glue (the Loctite gel control has rubber particles in it to make it less brittle), then applied epoxy around the fractured bit to consolidate it further (with 24h drying period between every step). So far it's holding well.
I learned a lot from that experience, in the unlikely event that I will have to repair another keyboard (in which case I will say suck it, I'll buy a new one.) Mastering silver ink is cool though, I might use it now instead of rewiring faulty traces on boards.