|Re: Varieties of magnetic cards|
Message #4 Posted by Thomas Chrapkiewicz on 25 Mar 2007, 11:44 a.m.,
in response to message #1 by Les Wright
The HP65 was my second HP calculator which I had purchased back in 1974.
The third type of card you mentioned is the original card that came with the HP65. If I recall correctly, a while after the 65 was available (yet before the 67 came to be), it was discovered by the user community that the cards could be used 'double sided'. You may find references to this in the old 'HP65 User Group' (later the 'PPC') publications. This method was not ever accepted/recommended by HP at the time. [If my memory is still working, I was member 852 if the HP65 group.]
I believe the first type you mentioned - the mostly white but not double sided was released before the 67. I'm not 100% sure on this - again studying the old HP65 Users Club publications would lend some insight here. I have not dug them up to study this myself.
The second type you mentioned was after the 67 release and HP had acknowledged (and used) double sided writing on the cards. The HP67 also allowed writing data to the cards which the HP65 did not.
I believe the HP Journal articles on the HP65 show roughly where the data track was written on the card. The 67 wrote the track in the same location - although a bit denser to hold the 224 steps as opposed to the 100 of the HP65.
I do recall someone making 'homebrew' cards which were usually quite poorly painted - usually different colors. We would use dry transfer lettering both on these and the 'official' HP cards to arrive at a quite asthetically pleasing card.
Keep in mind that the cards are 'formatted' as they are written - there is no hard track put on them until the data itself is written. I would often bulk erase (with an audio tape bulk eraser) the 65 cards before writing.
Perhaps I need to dredge up my archives and do some scans/pics if many out there are interested. Maybe there are other 'more mature' users out there that have some memories/recollections of these details to share!
Regards, Thomas Chrapkiewicz