> Well, if you're doing it without plating equipment, just solder a little bit
> of wire in the hole.

I new someone who used to fix Canon calculators that were done this way. Back in
the days of "standard" TTL gates and Nixie tubes, and small calculators required
their own desk these machines would go intermittent. The standard fix was to go
round and solder all the trough wires on all the boards.

It seemed the temperature cycling stressed the solder joints to a point where
the solder physically stressed enough to make a dry joint. This should not be a
problem with modern cooler running electronics.

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