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Full Version: Calculator key mechanics - Which design is more durable?
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Hi forum members,

only yesterday I took out two of my non HP-calculators, namely a Sharp EL-512 and an EL-512H. The first one was used by my father almost daily in office for as long as I can think, the latter was given to me by my father when I entered the Gymnasium (High School). Both saw really extensive use over many many years and still work like a charm especially the keyboards.

I never opened one of my Sharp calcs, but considering the almost total absence of tactile feel for their keys I'd presume, that there is almost no mechanics involved in the keyboard design. Does anyone know how the Sharp mechanics compares to that of the HP keyboard?

Furthermore, that made me wonder which key mechanics design philosophy is the more durable one? The Sharp design with almost now tactile feel but (presumably) very limited and simple key machanics, or the well known HP design?

All my HP calcs still feel pretty new, but I can recall a number of TAS auctions that stated sticky keys or keys that lost their typical "klick".

What is your experience/opinion about this?


Compared to which HP keyboard? HP has gone through many designs over the years.

Well, the keyboards I thought about are the ones I have experienced first hand, i.e. HP-41, HP-42S, HP-48GX, HP-15C.

As Eric mentioned, there were and are quite different keyboard technologies used in HP's calculators under the keyboard. Mechanics was very simple (and I guess it still is): the individual keys are held up by the force of a mechanical spring. This spring also produces the "snap" or tactile feedback. The very first in the Classics were gold-plated sheets of metal since apparently no domes were available ... I leave the details for others who have opened more calcs than me.