The Museum of HP Calculators

HP Forum Archive 04

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Mag Cards and Card Reader Repair
Message #1 Posted by Mike Davis on 4 Oct 2000, 11:25 a.m.

1) Is there a source for obtaining magnetic cards for the 71, 75, 67 or 41?

2) Are cards for 67 and 41 interchangeable?

3) I'm sure anything is possible, but is it likely that a card reader for the 67 can be repaired?

      
Re: Mag Cards and Card Reader Repair
Message #2 Posted by DaveJ on 4 Oct 2000, 12:32 p.m.,
in response to message #1 by Mike Davis

1) From other collectors either here (preferable) or EBay 2) Yes 3) Usually if it is just a mechanical problem like a gummy roller replacement or worm gear attachment issue. Electrical issues are more difficult

            
Re: Replacement wheels
Message #3 Posted by Mike Davis on 8 Oct 2000, 12:10 a.m.,
in response to message #2 by DaveJ

I have a 41CV reader that will not pull the card through. When I removed the card, it had some substance on the outer tracks (gum I guess). After a couple of tries, the cards were not coated with that gum but they still would not go through the reader.

If a card is not being pulled through the reader and the tracks indicate some gumming or whatever, can these wheels be found anywhere?

Where can they be found?

Is there any cleaning technique, to make these work without replacement? I mean is that the only non-electrical failure mode?

Or does one have to take one from another reader?

                  
Check out Dave's article
Message #4 Posted by Steve (Australia) on 8 Oct 2000, 2:01 a.m.,
in response to message #3 by Mike Davis

Dave the lost sheep wrote an excellent article (it's in the articles forum).

Here is a direct link to it...

http://www.hpmuseum.org/cgi-sys/cgiwrap/hpmuseum/articles.cgi?read=57

                  
Re: Replacement wheels
Message #5 Posted by Viktor Toth on 8 Oct 2000, 2:34 a.m.,
in response to message #3 by Mike Davis

Short answers:

The issue is not one of cleaning; it is a rubber wheel inside the card reader that chemically disintegrates (liquefies) due to age.

There are other non-electrical failure modes, but the symptoms you describe make it clear that in your case, it's the roller wheel that is the (only, one hopes) problem.

Taking a wheel from another reader is only a temporary solution, since your "new" reader is probably also a dozen or more years old. You need to build a new wheel.

Various techniques for doing so are described here at the MoHPC Web site and elsewhere. My preference is to use a silicon model airplane fuel line; a while back, I happened upon a specific type that serves as a perfect replacement (you just cut a slice and fit it on the gear shaft after removing the deposits left by the disintegrating rubber wheel.) Others swear by small rubber "O" rings that can apparently found in hardware stores (I never found any in Canadian hardware stores that are of the right size.)

Viktor

      
Re: Mag Cards and Card Reader Repair
Message #6 Posted by Andrés C. Rodríguez (Argentina) on 4 Oct 2000, 1:26 p.m.,
in response to message #1 by Mike Davis

The HP 41 Card Reader has functions that "translate" 67/97 opcodes into specific, XROM based functions. So the 41 + card reader combo is compatible with 67/97 cards. I don't think the 67/97 are backwards compatible with cards written in a 41. The 41/67/97 cards are physically the same, and the recording method and format are the same too; but the opcodes are different between 67/97 and 41.

            
Re: Mag Cards and Card Reader Repair
Message #7 Posted by Mike DAvis on 4 Oct 2000, 2:53 p.m.,
in response to message #6 by Andrés C. Rodríguez (Argentina)

I guess what I meant to ask is can a 41 card be reformatted to be read in the 67? So, if I had a 41 card could it be made to work with the 67 or are the cards preformatted and cannot be changed?

                  
Re: Mag Cards and Card Reader Repair
Message #8 Posted by Chris Catotti (Florida, USA) on 4 Oct 2000, 5:54 p.m.,
in response to message #7 by Mike DAvis

Yes they are interchangeable. No they are not preformatted. Please send me your mailing address and I'll send you some (from an opened pac, free).

                  
Re: Mag Cards and Card Reader Repair
Message #9 Posted by Viktor Toth on 4 Oct 2000, 9:26 p.m.,
in response to message #7 by Mike DAvis

Physically, the HP-41/65/67/97 cards are the same. There is no formatting required. No matter what calculator a card was used in, it can be reused in another calculator afterwards just like a blank card.

As for the logical format...

HP-65 format cards can only be written and read by the HP-65.

HP-67 and HP-97 cards are identical, and fully interchangeable.

The HP-41 can read (but not write) HP-67/97 style program and data cards (minor compatibility issues apply.)

Finally, only the HP-41 can write HP-41 style cards.

Viktor

                  
Re: Mag Cards and Card Reader Repair
Message #10 Posted by Reinhard Hawel on 6 Oct 2000, 6:37 a.m.,
in response to message #7 by Mike DAvis

I guess there are better experts on the 41 and 65/67 calculators, but the 71 and 75 cards are physically the same.

They have a timing track preformatted by HP. The 7x card readers have no possibility to format this track. The logical format is the same and if you saved your HP-75 BASIC programs as LIF (Text) files chances are, that you can read them into the 71 and transform them into 71 BASIC programs. Might be, that you have to change some commands slightly...

The hand-pulled concept with timing track had the advantage of higher bit density on the cards.

41 cards had to write the timing signals too, which generally leads to a higher redundancy level.

I'll have to search for the hpjournals describing the card reader technologies for getting the bit densities...


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