How to correct "loose" keys


I have a HP-45 which I intend to restore. One of the problems is that many of the keys are loose, so the whole thing rattles when the calculator is shaken (is this normal?) and some of them when pressed have kind of a soft feel. Does anybody have any suggestions? The anti-spill sheet of plastic is pretty worn out, but I'm not sure replacing it will help. TIA.




it's normal that the keys can 'rattle'.
Other than the newer HP calcs, the classic series (incl. the 45) has separate keys.

The 'soft feeling' when pressing a key can be the result of a broken metal contact 'switch' under the key.
The classic series doesn't have the round domes as switches,
instead they have something like metal 'bridges' where you press the key upon.
And these bridges seem to tend to break.

Sorry for my poor english, it's just too early to think straight;-)




Thanks for you input Raymond. I already checked the metal bridges on the keys that feel soft and they are not broken (yet) but some of them seem to be a little more worn out than the others. That is, they lost a bit on the curve and are flatter than normal.

Anybody out there have any suggestions as how to recover some of the spring curve? Thanks



I have not found any way to restore clickiness to a classic series key once it starts to go mushy. About the only thing one can do is to cut it off and solder a key dome from a scarpped machine in its place. This has its own set of problems and it can be tough to get a good match to the feel of the other keys. Thus iy should only be done as a last resort (i.e. the old key dome has split up one side).

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