Rubbery Bits Gone Gooey

From: Lawrence Walker <>
Date: Tue Nov 25 06:16:40 1997

On 23 Nov 97 at 10:35, Frank McConnell wrote:

> Lately a friend has been trying to copy a tape for an HP 2645
> terminal.
> Thus far he has discovered a problem with tape drives in two
> terminals. His description of the problem is that, when used, the
> motor capstan in the tape drive "melts". In one case he has not
> been able to get all the ex-capstan goo off of the belt capstan
> in the cartridge; fortunately that was a blank tape.
> My first thought was, hmm, this sounds like the problem the calculator
> folks have with the rubbery wheels that go gooey.
> I have one of these terminals too, but it's a bit buried in storage
> and I haven't got it out yet. (In fact, the tape contains games and
> he is trying to copy it because I expressed interest...of course, now
> I am thinking that when I dig the terminal out I need to open it up
> and check the capstans before I go and jam a tape in.) Instead I
> found the May 1976 issue of the HP Journal, which was smaller,
> lighter, closer to the front, and does a pretty good job of
> demonstrating how proud HP was of having fit tape drives to HP
> 264x terminals.
> What have I found out? The motor capstan has an aluminum core with an
> elastomer coating that is ground to the right size during
> manufacture. Said elastomer was chosen for quick recovery from the
> dent that forms in it when the loaded tape isn't moving (as the
> capstan is held against the tape cartridge's belt capstan).
> So now I guess I have two questions. One is just what do the
> calculator folks do about rubbery wheels gone gooey? And the other
> is, can I do something like that for these drives? Given that the
> object of this capstan is to press against and drive something less
> flexible than a magnetic card (the belt capstan in a DC100 tape
> cartridge) I'm not sure the same sort of material would work.
> And an observation: the HP 9815A desktop calculator I have sitting here
> seems to use a similar drive (at least the capstan looks similar when I
> peer in the slot), and I think the HP 85 does too.
> -Frank McConnell
 You could try the mechanical calculator mailing list. There's a lot
of extremely knowledgeable former repair people and collectors who
restore old calculators on it. I don't have the address handy but it
should be easily found as many also have web pages.

ciao larry
Received on Tue Nov 25 1997 - 06:16:40 GMT

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