On Sun, 02 Aug 2009 11:28:04 -0700, "Paul Hovnanian P.E."
wrote:
This isn't really an electronics repair problem. It might be better solved
on an HP calculator discussion group, if anyone knows the whereabouts of a
decent one.
I collect HP calculators. Good sites to ask such questions a
http://www.hpmuseum.org
http://www.hp41.org
I have a card reader for an HP-41C calculator (an HP 82104A).
Ummm.... the 82104A is the model number of the card strip reader.
I took it out
of storage (a zip lock bag kept in a desk drawer) the other day and plugged
it in. When I fed a card through it, the card jammed and, when I pulled it
out, it had a streak of sticky goo on it. So I disassembled the reader.
It appears that the little rubber(?) wheel that feeds cards through (driven
by a motor and worm gear) has decomposed into the aforementioned sticky
goo. What were these things made out of? What would cause them to decompose
like this? Moisture? How much could there be in a sealed zip lock bag? What
would be a suitable material to use to fashion a new wheel (about 3/8" diam
by 1/8" wide).
Yep. It's a common problem. The rubber breaks down and turns to
incredibly sticky goo. I've repaired several HP65 calculators with a
similar problem:
http://802.11junk.com/jeffl/pics/hp65/index.html
Note the photo of the drive roller.
http://802.11junk.com/jeffl/pics/hp65/slides/Hp65-Drive-Roller.html
It's actually a piece of hardware store vinyl tubing, carefully cut to
length with a razor blade or surgical scalpel. (An Xacto knife is not
sharp enough). I impaled a piece of tubing on a metal rod that fit
the center hole, stuffed it into a drill press running at the slowest
possible speed, and carefully cut pieces to length with a razor. There
are probably better ways to do this, but I only needed one roller and
didn't mind destroying a few more in order to get one that was
perfect.
I've had zero luck with the o-ring replacement, which tends to slip
because of insufficient contact area. I also lightly sandpapered the
surface of the vinyl tubing in order to prevent slipping. I'm not
sure if this was really necessary, but it can't hurt. Just remove the
glaze and don't gouge the surface. It's easiest to do lengthwise
along the tubing when skewered by a metal rod before cutting to
length.
I also have in front of me an HP41CX with the card reader module. The
internal construction is similar to the HP65. I haven't found the
need to repair any yet so I have no experience with these. Here's a
web site with photos and instructions:
http://forum.hp41.org/viewtopic.php?f=2&t=73
http://www.pmgeiser.ch/calc/index.php?id=HP82104A
http://www.hpmuseum.org/cgi-sys/cgiwrap/hpmuseum/articles.cgi?read=57
http://www.hpmuseum.org/cgi-sys/cgiwrap/hpmuseum/archv001.cgi?read=2497
It looks very similar to the HP-65 so I suspect that the vinyl tubing
replacement should work. If you take it apart, be sure *NOT* to lose
the tiny plastic balls sandwitched inside the reader mechanism. I've
spent hours on the floor looking for where I dropped them.
I don't want to speculate on the cause of the rubber deterioration.
--
Jeff Liebermann
150 Felker St #D http://www.LearnByDestroying.com
Santa Cruz CA 95060
http://802.11junk.com
Skype: JeffLiebermann AE6KS 831-336-2558