Repairing pre-recorded program cards for HP-65,HP-67, HP-97, HP-41C


I just wanted to share a trick I came up with to fix HP pre-recorded cards that have had their data erased or damaged. Every now and then, I have a problem reading a card with my HP-65 or HP-67/97. Sometimes it is only one side that is un-readable. This trick may not work if the magnetic strip is physically damaged. The basics: Each corner of the card has a diagonal cut for write protection of that particular side of the card. The trick is to build up the corner with scotch tape so that it engages the write cicuitry of the card reader. I begin by applying one strip of tape on one side of the card over the cut corner. I usually lay about 3 mm of tape on the card, and the tape extends over the corner. Then I trim the tape using scissors to form the corner.Next, I build up the corner on the other side by applying at least 4 layers of tape ONLY OVER THE CORNER SECTION. Do not apply any more tape over the magnetic card because it will make the card too thick to get through the card reader. After each application, trim the excess tape to make a nice rigid corner. If the problem on the card is side one, you are in luck because you only have to cover the side 1 corner. If the problem is on side 1 and side 2 or just side 2, then you have to cover both corners. The reason for this will be clear below. On the HP-65 you only have one side to worry about. Next enter as much of the program that you can by running the card through the calculator with the program switch set at "run". You will obviously get "error" trying to run the card through the bad side. Next, enter the remainder of the program by hand. You will need the program listing from the application pac manual. Next, set program switch to "w/prgm". Even if side one of your card was ok, you need to run it through the data write cycle here. This will instruct the card to add the "crd" instruction . If you don't run side 1 first, it will put the "crd" instruction on side 2. Finish by running side 2 through the card reader. If the card gets jammed, you may have added too much tape to the corner. You will need to use another card to help push the card through.

That's it. Switch the program switch back to "run" and try the card. If it works, remove the tape. It has helped me save several pre-recorded cards. Please, I do not want to accept any liability if you damage your card reader or calculator. Please perform this operation at your own risk.


Of course, on the HP-41 you can just set flag 14 and it will allow you to record on a card even if the corners have been clipped off. (I don't believe there is an equivalent flag on the 65 or 67/97.)


Maybe this piece can be moved to the articles forum...


to the articles forum for long-term keeping?

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