I just got a TI-81 and TI-82 on eBay, and both have nonworking keys. On the TI-82, the [SIN] key and below don't work, and on the TI-81 the 2, ., and (-) keys don't work.
On both there was battery leakage, corroding some of the exposed key traces away. How do I reconnect the thin wires going from a key contact to the adjacent key? Do I just use a little blob of solder?

Edit: Some of the connections on the TI-81 that go through the PCB are missing from the corrosion, so they're empty holes. Can this be repaired?

It's hard. I usually strip a little of the trace, solder on a 30-awg wire, find a place on the other side of the discontinuity, and connect the other end. The hard part is often cutting a nick in the edge of the board to pass the wire from front to back.

The TI-81 will have to wait until I improve my soldering, but the TI-82's damage is minimal and the furthest connection that has to be made is about a millimeter. That one needs the most help for now; how do I do that fix?

Maybe that trace pen that I can find at my electronics store will do the trick for the 82, but that costs more than my calculators I just got. Either way, it'll be worth it, considering the cost of a working 82. Perhaps the robotics class will have one.

Strip the area and try dropping some solder on. If you can't get it to bridge neatly, put a tiny piece of 30awg conductor (without the plastic) in place to help the solder's surface tension break.

If trace pen doesn't work, I'll solder that connection.

Edit 11/18/12: It did work, once it was protected from the keypad rubbing away the CircuitWriter.



Edit 2: The TI-81 will be ready about 6 hours after the TI-82 was finished. I didn't finish it (intentionally) and just now finished the last connection. Hopefully I didn't short out anything.

Edit 3: The TI-81 is finished and working! I flooded the plated through holes that were destroyed by the corrosion with CircuitWriter ink, and it worked wonderfully.