Just bought a HP-67 calculator at an auction

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(07-29-2020 12:38 PM)rprosperi Wrote:  It's interesting that this problem, common to all old HP (and TI) machines, remains pretty much unexplained, other than the overly simple "the rubber eventually turns to goo", which is not something commonly happening to other similar vintage products. My cassette deck has bands and capstans with rubber 'wheels' which may have hardened or gotten brittle, quite the opposite of turning to goo. I'd like a materials science engineer to comment if this is really typical or perhaps a unique phenomenon.

The fuel-cell 'sealant' used on the F-111 would consistently 'revert'; kept the fuel barn at RAF Upper Heyford gainfully employed. Perusal of REVERSION STUDIES OF NATURAL AND GUAYULE RUBBERS {DTIC A-A257 501} is a start on understanding the many causes of 'reversion' in rubber, plastic, etc compounds.

BEST!
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