Gummy card reader wheels - again


I was reading the Oct 8,2000 forum thread here about gummy
65, 97, and 67 (and even 41 I guess) card reader wheels
and the oxidation problem that causes them to gum up.

Is there any evidence to show that perhaps this was a
problem that was dependent on HP's supply of wheels from
the manufacturer? In other words, were there some batches of
wheels that oxidize in this manner and others that don't?
I ask because I've seen a fair share of older and newer 65s,
67s, and 97s and you'd think that all the older calcs would
have this problem but there are some older ones thats are just

Maybe a environment issue? Perhaps ones in the southwest last
longer in the same way that older cars don't rust out and
deteriorate as fast in the SouthWest, USA?

Any ideas?


This is an intresting question, I saw some HP-67 with back label untouched and card reader fully functioning. May be also the card reader was serviced and then the back label could be replaced (I even have a factory new back instruction label).

The problem is concerning also to the material used, en fact HP-65 wheel is made with natural rubber but the TI SR-52 I have from the same era, has a green rubber wheel that's still in good order, the material is really different, the TI wheel seems to be a "modern" rubber insensitive to the environment.

However all my calculators "with wheels" are stored in a controlled environment show-case with many anti-moisture bags.


In my experience, HP card readers deteriorate fairly consistently, almost like clockwork (when you encounter a machine with a longer-living reader, don't be surprised if, when you finally open it, you find a late 1970s service sticker inside.)

Environmental conditions have little effect (although I did notice that the appearance of the deteriorated material is different in calculators also have other forms of corrosion.) TI on the other hand appears to have used a variety of materials, some of which deteriorates, some of which hardens, and yet other wheels still look like new after 25+ years.



I have only seen about 10 67s. I have seen a few that work just fine. There was no signs of gummy wheels at all. BUT, I took them apart to replace the wheel anyway and found that these working wheels were soft and appeared near to being a problem.

I even got one 41 (which is newer) card reader that was NIB and still in it's original packing. It was bad right out of the box.

I suspect they are either 1) Bad, 2) Bad but fixed or 3) soon to go bad.


Peter, This is an interesting subject. I have had my hp67 since my wife purchased it for me on Christmas of 1977.
This calculator has never been serviced! I use it in coal fired power plants during outages to perform boiler service calculations. It goes with me when I crawl over boiler tubes covered in fly ash, also on my hands when I load a magnetic card. Fly ash is very corrosive, and abrasive. The very atmosphere is corrosive as evidenced by battery terminals in flashlights becoming corroded after a week or so. My hp67 has never failed me, and I have NEVER had a card read error. I use it to this day on a daily basis. I have never had the calculator open, so I can not tell you what type of wheel is in there, but if it ever goes down, I will take it apart. Bill.


If these wheels fail "like clockwork" as a previous poster
has suggested and if even some HP 41 card readers have
had this problem out of the box as another poster has
said, then why would I have a mint HP 65 that I acquired
from the original owner, with a serial number date code
of 1333A i.e. made in '73, and that I know was never
repaired or opened, and yet it has a card reader that works
flawlessly with no evidence of residue on the cards that
are passed through it??


I may well be wrong on this. I am certainly NO expert on this subject. But I have done quite a few of these repairs on these recently.

But I took a working HP67 apart because I suspected that the card reader actaully needed repair. I had no evidence to justify this. Cards were pulled through the reader. Cards read and wrote properly. Cards had no signs of gummy substance. And no, I don't do that anymore, if it works and the label is undisturbed.

But what I found on the good working 67 card reader, was a very soft wheel. When I removed the wheel reisdue, it was all gummy underneath. There was a thin film of dried gum that let it work. BUT, it was all gummy underneath that surface.

I suppose it is also possible that different models had different substances. But the 67s and 41s that I have seen have all had the problem.


Very interesting...some older reader have had the wheel go
sticky and gummy and then get covered with some dried gum somehow?
I wonder if these old wheel with the dried gum around the wheels will
just continue to be fine indefinitly, like the dried gum is
now acting as a proective surface or something.

I think we need to finance a study. :)


I have just received a nearly mint hp-67. It has a card reader that works just fine. There is no sign of any gumming. The reader reads and writes and is very quiet.

Because it is in such nice condition and the label has never been touched, I'm hoping that you are right and I might not ever have a problem.

Here's to being wrong:-)

Possibly Related Threads...
Thread Author Replies Views Last Post
  Reasonable price for a 41C, Quad Mem, Time, Navigation and Card reader module? Eelco Rouw 10 1,590 12-12-2013, 01:52 AM
Last Post: Eelco Rouw
  hp-67 card reader problem. Marcel Samek 5 990 12-09-2013, 09:09 PM
Last Post: Paul Berger (Canada)
  HP-97 card reader pinch roller axle davorin 2 577 09-15-2013, 08:47 AM
Last Post: aj04062
  HP-97 Card Reader davorin 3 613 09-13-2013, 04:21 PM
Last Post: Stephan Matthys
  HP-67 Card Reader Repair Question aj04062 1 498 08-08-2013, 11:15 AM
Last Post: Randy
  Hp-67 card reader: tantalum capacitor identification Ignacio Sánchez 8 1,189 06-02-2013, 07:26 PM
Last Post: aj04062
  Testing card reader motor for 65 Michae Altmann 2 566 03-17-2013, 09:24 PM
Last Post: Randy
  Repaired HP-97 card reader doesn't show any signs of life jbssm 6 913 02-17-2013, 03:15 AM
Last Post: Alberto Fenini
  HP 65 card reader problem H Fischer 3 598 11-24-2012, 12:11 PM
Last Post: H Fischer
  41CL and Card reader Prabhu Bhooplapur 3 604 10-18-2012, 07:40 AM
Last Post: Ángel Martin

Forum Jump: