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 have a card reader for an HP-41C calculator (an HP 82104A). 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).

--
Paul Hovnanian
----------------------------------------------------------------------
Have gnu, will travel.

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 have a card reader for an HP-41C calculator (an HP 82104A). 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).

Any help? :-
http://www.hpmuseum.org/cgi-sys/cgiw...s.cgi?read=154

JC

On Sun, 02 Aug 2009 11:28:04 -0700, Paul Hovnanian P.E. wrote:
This isn't really an electronics repair problem.

Well, it certainly is WAY MORE On Topic than:
"a Hiroshima size nuke detonated 100-300 miles over the CONUS..."

Archon wrote:

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 have a card reader for an HP-41C calculator (an HP 82104A). 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).

Any help? :-
http://www.hpmuseum.org/cgi-sys/cgiw...s.cgi?read=154

JC

That was a good lead. The model addressed has different sized drive
wheels, but this site lead me to one that suggested silicone rubber
tubing for a repair.

Thanks.

--
Paul Hovnanian
------------------------------------------------------------------
There's plenty of room for all God's creatures. Right next to the
mashed potatoes.

The wrong compound. Back in '87, my GF had a very expensive B&O stereo
setup. Paid aTon for these "top drawer quality" components. After 3
years of little use, , the turntable made a scraping sound. I took it
apart, and found the rubber bushings the drive motor was mounted in
had deformed from the minute tension of the belt. The drive cog was
running against the motor bracket. B&O said "tough bananas".Some
quality.
A friend of mine had a 3 yr old Range Rover. The dash material cracked
and split Badly in this time. RR refused to warranty it.
Sheesh.
JR


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 have a card reader for an HP-41C calculator (an HP 82104A). 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).
HOME PAGE:
http://www.seanet.com/~jasonrnorth
--------------------------------------------------

Paul Hovnanian P.E. wrote in message
...
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 have a card reader for an HP-41C calculator (an HP 82104A). 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).

--
Paul Hovnanian
----------------------------------------------------------------------
Have gnu, will travel.


Most "electronic" repair is nothing to do with electronics, its failed
solder/connections/corrosion/failed rubber.
Has anyone ever seen an only partly perished to goo, rubber part? no always
total. Not only that but if one piece has failed then mre than likely others
have failed inside the same kit. What is the contagion that passes between,?
a gas? atmospheric contaminant?. I've got a box of salvaged rubber belts ,
and poured a load of talcum powder in there and stirred about. None have
since perished, perhaps an interesting pointer to what is going on, but I
still don't know what.

--
Diverse Devices, Southampton, England
electronic hints and repair briefs , schematics/manuals list on
http://home.graffiti.net/diverse:graffiti.net/

"Paul Hovnanian P.E." wrote in message
...
Archon wrote:

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 have a card reader for an HP-41C calculator (an HP 82104A). 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).

Any help? :-
http://www.hpmuseum.org/cgi-sys/cgiw...s.cgi?read=154

JC

That was a good lead. The model addressed has different sized drive
wheels, but this site lead me to one that suggested silicone rubber
tubing for a repair.

Thanks.

--
Paul Hovnanian
------------------------------------------------------------------
There's plenty of room for all God's creatures. Right next to the
mashed potatoes.

I was thinking originally that you might be able to rework the tyre from a
cassette machine pinch roller, but silicone rubber tubing might be a viable
alternative. I have used this for all sorts of little mechanical jobs like
this, and it seems to be pretty resiliant mechanically, and resistant to
chemical breakdown. I have it in several sizes that came to me from a coffee
machine outfit that I repair control boards for. It is semi-clear food
grade. If you have any trouble finding a source for a small amount, the
vending machine industry might be a good place to look.

Arfa

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

In article ,
Paul Hovnanian P.E. wrote:

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).

I had a similar problem with an HP flat-bed plotter. The pressure
"tires" for the forward-and-back paper motion had failed while the
plotter was in long-term storage... the rubber had become gummy, and
had developed a bad dent on one side where they had been pressing
against the motor-operated drive wheels.

From looking at them, I'd guess that they were composed of a synthetic
rubber of some sort (I have no idea which formulation) and that the
deterioration could have been due to long-term ozone exposure.
Zip-lock bags are not, I think, proof against long-term diffusion of
either moisture or ozone.

The parts are, of course, completely unobtanium at this point... the
plotter is long past its end-of-life date.

I found that the tires had actually been molded onto the bearing
(which has small ribs in it which engaged the rubber). I cut and
scraped the rubber off of the bearing.

Molding on a new rubber layer didn't seem terribly feasible. However,
at a local modeling-and-crafts store I found an acceptable
substitute... a soft, flexible tubing made of a translucent blue
silicone rubber of some sort, intended for use as a fuel line on
radio-controlled airplanes. I was told that it's highly stable stuff,
not attacked by volatile RC motor fuel.

I bought a foot of the right-diameter stuff, cut a piece for each
bearing, and squeezed the bearing inside. Instant "tire" - perhaps
not quite as perfectly circular as the original, but close enough that
the plotter now works fine.

--
Dave Platt AE6EO
Friends of Jade Warrior home page: http://www.radagast.org/jade-warrior
I do _not_ wish to receive unsolicited commercial email, and I will
boycott any company which has the gall to send me such ads!

Arfa Daily wrote:

"Paul Hovnanian P.E." wrote in message
...
Archon wrote:

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 have a card reader for an HP-41C calculator (an HP 82104A). 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).

Any help? :-
http://www.hpmuseum.org/cgi-sys/cgiw...s.cgi?read=154

JC

That was a good lead. The model addressed has different sized drive
wheels, but this site lead me to one that suggested silicone rubber
tubing for a repair.

Thanks.

--
Paul Hovnanian
------------------------------------------------------------------
There's plenty of room for all God's creatures. Right next to the
mashed potatoes.

I was thinking originally that you might be able to rework the tyre from a
cassette machine pinch roller, but silicone rubber tubing might be a viable
alternative. I have used this for all sorts of little mechanical jobs like
this, and it seems to be pretty resiliant mechanically, and resistant to
chemical breakdown. I have it in several sizes that came to me from a coffee
machine outfit that I repair control boards for. It is semi-clear food
grade. If you have any trouble finding a source for a small amount, the
vending machine industry might be a good place to look.

Good tip. I bought a chunk of it at the local hobby shop. But the center
hole isn't concentric with the O.D. So the 'wheel' is lopsided and the
card moves jerkily.

A few bucks more for higher quality stuff is worthwhile.

--
Paul Hovnanian
------------------------------------------------------------------
Porsche 928: 0 to c in 2.125 years, 2.435 light-years per mile^3 of gas

Jeff Liebermann wrote:

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 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.

Vynil. Hmm. I'll keep that in mind. I saw a similar fix using silicone
tubing, but the stuff I bought at the hobby shop is not concentric, so
it made a lopsided wheel.

The vynil my h/w store carries is all 'lumpy' (due to storage on a reel,
probably) so its more a matter of buying quality materials, whatever
they are.

A few bucks more per foot isn't going to break the bank when all I need
is a few inches.

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 didn't see any plastic balls in the 82104A . A couple of plastic
switch actuators and a nylon roller. But I've gotten pretty good at
pulling this thing apart.

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

--
Paul Hovnanian
------------------------------------------------------------------
Applying information technology is simply finding the right wrench
to pound in the correct screw.

On Wed, 05 Aug 2009 19:04:49 -0800, "Paul Hovnanian P.E."
wrote:

Vynil. Hmm. I'll keep that in mind. I saw a similar fix using silicone
tubing, but the stuff I bought at the hobby shop is not concentric, so
it made a lopsided wheel.

Defective. I checked the tubing I bought for concentricity and it was
perfect. Having a variable wall thickness means the tubing is junk.

The vynil my h/w store carries is all 'lumpy' (due to storage on a reel,
probably) so its more a matter of buying quality materials, whatever
they are.

It won't matter much because you're only cutting off a very small
piece. If it bothers you, impale it with a suitable stiff rod and hit
it with a heat gun. It should straighten out.

A few bucks more per foot isn't going to break the bank when all I need
is a few inches.

Well, I don't know about the different formulations. I wanted
something that was both the right size, reasonably hard, and fairly
compressible in order to get a large enough contact area with the
magnetic strip. Rubber chemistry hose was too soft. Rubber
automotive gas line hose was too hard. Some other strange rubber
tubing I found would take a compression set, which would cause erratic
motionn due to the flat spot. Only clear vinyl tubing didn't have
these problems.

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 didn't see any plastic balls in the 82104A . A couple of plastic
switch actuators and a nylon roller. But I've gotten pretty good at
pulling this thing apart.

Oops. The HP65 certainly has a few plastic balls inside, but maybe
the HP41C does not. Dunno.

"Paul Hovnanian P.E." wrote in message
...
Jeff Liebermann wrote:

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 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.

Vynil. Hmm. I'll keep that in mind. I saw a similar fix using silicone
tubing, but the stuff I bought at the hobby shop is not concentric, so
it made a lopsided wheel.

The vynil my h/w store carries is all 'lumpy' (due to storage on a reel,
probably) so its more a matter of buying quality materials, whatever
they are.

A few bucks more per foot isn't going to break the bank when all I need
is a few inches.
Paul Hovnanian


Here's another thought, Paul. I recently had to replace the fuel line on my
garden lawnmower, and the replacement stuff that I got had a small bore, and
a thick rubber wall which, without actually measuring it, looks to be pretty
even for thickness

Arfa

Jeff Liebermann wrote:

On Wed, 05 Aug 2009 19:04:49 -0800, "Paul Hovnanian P.E."
wrote:

Vynil. Hmm. I'll keep that in mind. I saw a similar fix using silicone
tubing, but the stuff I bought at the hobby shop is not concentric, so
it made a lopsided wheel.

Defective. I checked the tubing I bought for concentricity and it was
perfect. Having a variable wall thickness means the tubing is junk.

Yep. Junk. The error in concentricity is visible with a cheap magnifying
glass. I found another hobby shop and picked up a foot of silicone
tubing (the stuff they sell for model a/p fuel lines). It looked good
and works fine.

Getting a concentric wheel on the mag card drive is critical. A bump a
few thousandths too high and the added friction slows the drive down
enough to cause a read error. A few thousanths too low and the card
slips.

My initial try with the new tubing appeared not to work (jerky card
feed). But when I took a close look at my new wheel, I could see that I
hadn't cut the end of the tubing exactly square. So when I slid it
against the little shoulder on the axle, one side of the tubing was
compressed more than the other and, as a result, ushed up as a high
spot. I just slid it back off the shoulder a few thousanths of an inch
and it works just fine now.

The vynil my h/w store carries is all 'lumpy' (due to storage on a reel,
probably) so its more a matter of buying quality materials, whatever
they are.

It won't matter much because you're only cutting off a very small
piece. If it bothers you, impale it with a suitable stiff rod and hit
it with a heat gun. It should straighten out.

A few bucks more per foot isn't going to break the bank when all I need
is a few inches.

Well, I don't know about the different formulations. I wanted
something that was both the right size, reasonably hard, and fairly
compressible in order to get a large enough contact area with the
magnetic strip. Rubber chemistry hose was too soft. Rubber
automotive gas line hose was too hard. Some other strange rubber
tubing I found would take a compression set, which would cause erratic
motionn due to the flat spot. Only clear vinyl tubing didn't have
these problems.

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 didn't see any plastic balls in the 82104A . A couple of plastic
switch actuators and a nylon roller. But I've gotten pretty good at
pulling this thing apart.

Oops. The HP65 certainly has a few plastic balls inside, but maybe
the HP41C does not. Dunno.

None that I saw. But there's enough little springs and things that the
advice still applies. One the goo is cleaned out of the reader, the two
halves and a curcuit card don't need to be disassembed on the HP 41C
reader anymore. The drive wheel is acessible from one side. So, as long
as the new wheel doesn't decompose and its remaons need to be cleared, a
subsequent wheel replacement will be pretty simple.

--
Paul Hovnanian
------------------------------------------------------------------
Big business never pays a nickel in taxes, according to Ralph Nader, who
represents a big consumer organization that never pays a nickel in
taxes.
-- Dave Barry

On Fri, 07 Aug 2009 16:34:26 -0800, "Paul Hovnanian P.E."
wrote:

My initial try with the new tubing appeared not to work (jerky card
feed). But when I took a close look at my new wheel, I could see that I
hadn't cut the end of the tubing exactly square. So when I slid it
against the little shoulder on the axle, one side of the tubing was
compressed more than the other and, as a result, ushed up as a high
spot. I just slid it back off the shoulder a few thousanths of an inch
and it works just fine now.

I don't think it will stay that way. It's going to move back and
forth along the shaft. As I vaguely recall, the ID the vinyl tubing I
used was just a bit too large for a snug fit on the shaft. I had to
glue is with some kind of rubber cement to keep it from sliding and
spinning.

I did quite a bit of tinkering in order to get the tubing cut squarely
and the right size. I shoved a metal skewer down the center and spun
the tubing in a drill press at the slowest possible speed. I used a
razor blade or scalpel to cut it square. An Xacto knife was not sharp
enough. I also broke the sharp edge of the tubing to prevent lumps.

I didn't have any probem with jerky feeds or errors with the
replacement roller. The trick was to deglaze the surface. You
shouldn't have to do that with a rubber tube, unless it's shiny.

None that I saw. But there's enough little springs and things that the
advice still applies. One the goo is cleaned out of the reader, the two
halves and a curcuit card don't need to be disassembed on the HP 41C
reader anymore. The drive wheel is acessible from one side. So, as long
as the new wheel doesn't decompose and its remaons need to be cleared, a
subsequent wheel replacement will be pretty simple.

Thanks. I anticipate doing the same thing to my HP41CX eventually.
Good to know that it's easier than the HP65.

--
Jeff Liebermann
150 Felker St #D http://www.LearnByDestroying.com
Santa Cruz CA 95060 http://802.11junk.com
Skype: JeffLiebermann AE6KS 831-336-2558

Paul Hovnanian P.E. wrote in message
...
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 have a card reader for an HP-41C calculator (an HP 82104A). 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).

--
Paul Hovnanian
----------------------------------------------------------------------
Have gnu, will travel.


Hello, and I would just add that this was also a common problem (after a
number of years of use) on the Texas Instruments TI-59 calculator.
Happened to me. I guess after 30 years of just occasional use things
start to decompose (just like with people). There was a fellow offering a
TI-59 card reader repair kit on flea-bay consisting of a replacement
(nylon?) wheel and a CD ROM with instructions. Perhaps a rubber faucet
washer close in size could be reshaped to provide the correct
inside/outside diameter. Hadn't previously heard of this problem on
vintage HP card reading/writing calculators, though. Sincerely,

John Wood (Code 5550) e-mail:
Naval Research Laboratory
4555 Overlook Avenue, SW
Washington, DC 20375-5337