Dodgy HP-10BII 'FV' key theory Message #5 Posted by Frank Wales on 10 Feb 2003, 5:01 p.m., in response to message #3 by Dave
I have a theory about the 'FV' key feeling consistently mushy on the 10BII, but to see what I mean, you might need to dismantle yours (which invalidates your warranty, etc., and might leave you with a non-functioning machine, for which I take no responsibility -- if you're not comfortable dismantling calculators, don't do this).
First, take the machine apart; it's just held together by three clips down each side, two at the top and one at the bottom -- insert a thin blade between the case halves and twist repeatedly, and you'll be able to pop the case open.
Note that there are four heat stakes around the battery contacts on the main board; these hold it in place against the front half of the unit. Note also that the keyboard frame is attached to the main board by two further smaller heat stakes, one at the top left of the main board, and one at the bottom right. If looking at the keyboard from the front (printed) side, the lower one is about at the
intersection of the 'C', '1', 'ON' and '0' keys, and the other is right below the right-hand hinge of the 'FV' key.
You can get a better idea of all this by cutting the heads off the heat stakes, and really dismantling the calc; if you don't do this, you'll be able to reassemble the calculator as if it had never been opened, but cutting the heat stakes can't be undone, and will leave you with a slightly looser machine upon reassembly. Anyway...
My theory, alluded to earlier, is that the stake right below the 'FV' key is having a bad mechanical effect on the key, either distorting the plastic frame around it, or pushing one side of it too close to the plastic dome underneath, or something similar which affects its ability to interact properly with the dome and the contacts underneath it. I don't think it helps that there are only two diagonally opposed heat stakes on the keyboard instead of the four that seem to have been planned for (there are four holes in the main board that look like keyboard stake holes).
If there's a mechanical engineer in the house who could comment on this one way or the other, I'd be interested in their opinion, especially as regards how predictable this problem would have been from the design, prior to manufacture.
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