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HP 42S - wobbly "+" key - Printable Version

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HP 42S - wobbly "+" key - reach - 09-17-2019 04:50 PM

I stopped using my beloved 42S because the "+" key works pretty unreleable. The developer of the fanrtastic "Free42" Android app told me that there is a fair chance to fix this and that this forum should have good tips for doing this.

I did use the search function but no hits, maybe I used the wrong words. Anyway, is there really somebody who could help me? I found one video online that shows that opening it has some irreversible impact (rivets no longer holding it together). But I assume opening it is the only way to clean it, right?


RE: HP 42S - wobbly "+" key - mfleming - 09-18-2019 01:13 AM

If the is no mechanical damage to the key (that is, the hinge at the bottom of the key and the dome beneath the key are unbroken) and keypresses are intermittent, then there may be debris beneath the key that is preventing electrical closure when the key is pressed. A drop or two of DeoxIT Red or other contact cleaner put into the key opening followed by exercising the key a few dozen times may clear away the debris. You'll notice the key closure gradually improves with use if this is the case.

I believe other repair methods do require opening the case, but if opened carefully the case can be closed and not feel loose or rattle when handled. I've done repairs on Pioneer calculators and you'd have to check the rivits beneath the battery cover to know the case had been opened. There are several good articles about repairing Pioneers in the old article section (go to the Articles forum and check for a link to the old section in the introductory text at the top of the page).

Good luck bringing that old friend back!