HP CArd Readers - Longevity

[larthurl]

As most people here know, the card readers in the HP-65, HP-67, HP-41 and others become non-functional after 20, 30 or 40 years. The wheels (rubber?) used to transport the card turn to goo or at the least become soft.

Do you think HP never imagined these calculators working for decades and therefore didn't use better (and more costly) material in the card reader drive mechanism? Was there even better material in the 1970s and 1980s? And for the card readers that are getting re-built today with O-rings, how long will these O-rings last?

Just curious.

[Maximilian Hohmann]

Hello!

(11-24-2017 05:35 PM)larthurl Wrote:  As most people here know, the card readers in the HP-65, HP-67, HP-41 and others become non-functional after 20, 30 or 40 years. The wheels (rubber?) used to transport the card turn to goo or at the least become soft.

It is not just the pocket calculators but the same applies to desktop calculators and laboratory equipment costing up to 100 times as much. Their card readers and tape drives suffer from the same problem.

(11-24-2017 05:35 PM)larthurl Wrote:  Do you think HP never imagined these calculators working for decades and therefore didn't use better (and more costly) material in the card reader drive mechanism?

That's a question only the engineer(s) in charge will be able to answer. My guess would be that a combination of two factors comes together:
1. The technical advance since the second half of the 20iest century has been so fast that few electronic products are used for more then a coulpe of years. Therefore they are no longer designed for "infinite life" (as it would be called in my sector: aeronautics). Just look at today's smartphones and cameras which will be replaced whilst still in perfect operational state and still 98% state of the art. Insanely crazy.
2. No long-term stability data were available for the rubber used in those drives.

(11-24-2017 05:35 PM)larthurl Wrote:  Was there even better material in the 1970s and 1980s?

Most of the materials used today for such parts, e.g. silicone rubber, nitril, polybutadiene, ... , have been around long before "our" card readers were made. Would they have lasted longer? Who knows.

(11-24-2017 05:35 PM)larthurl Wrote:  And for the card readers that are getting re-built today with O-rings, how long will these O-rings last?

It depends on the material the O-rings are made of. There are is a wide variety to chose from.

Regards
Max

[Garth Wilson]

In 1982-83, I worked as a repair technician at TEAC/Tascam in Montebello, CA. Any tape recorder that came in for repair, regardless of what for, got the rubber parts replaced, to make sure it shipped with the maximum life expectancy. These included, #1, belts, #2, rubber wheels, idlers, etc., and #3 pinch rollers. Pinch rollers last the most years.

I have a Sony open-reel tape transport here from the 1960's with the original pinch roller. It's pretty hard, but it still works. (Fortunately this transport has no belts.) Pinch rollers themselves aren't what's pulling the tape though, in the way the card-reader roller pulls the card. They really just press the tape against the capstan. Different kind of rubber, I guess.

My TI-59's card reader's rubber wheel died many years ago.

[Kees Bouw]

Very interesting stuff, the ageing of plastics. Some plastic discolours to brown, some plastic disintegrates like the magnetic card drive rollers, some plastics become very hard like the paper transport rollers of a HP-97 printer, and recently I have had HP-67 keys become very ugly after cleaning with warm water and soap, showing many white cracks where the keys have been exposed to light (see attached pictures). Right now I am having difficulty cleaning the case of a HP-67. On the areas where it has been held there is white tarnish, maybe acid from sweat or skin fat has affected the plastic if such a thing is possible. I have not yet found the right means to get this off.
I would welcome a "plastic historian" to explain these phenomena along with some advice how to treat the various kinds of ancient plastic.

[Sukiari]

(11-29-2017 07:58 PM)Kees Bouw Wrote:  Right now I am having difficulty cleaning the case of a HP-67. On the areas where it has been held there is white tarnish, maybe acid from sweat or skin fat has affected the plastic if such a thing is possible. I have not yet found the right means to get this off.
I would welcome a "plastic historian" to explain these phenomena along with some advice how to treat the various kinds of ancient plastic.

I too am having this white tarnish issue on my 67, it's a real bummer. Any help would be appreciated, I'm afraid to use any commercial products on it.