Repairing an HP-65


Hi all,

I'm trying to repair an HP-65 calculator, but it's exhibiting a strange behaviour. Every 2nd key I press it displays 9.99999999E99 ... or something like that.
So, if I press '4', 1st it displays the 4, then if I press '4' again it displays 9.99999999E99.
I opened the unit and I noticed the yellow cable near the card reader is out of it's place (I think this is not the problem cause it only affects the card reader, right?) anyway, can anybody tell me were the yellow cable plugs?
The part unplugged is unfortunately inside that foam rectangle, and I have no idea were I should put it :s

Thank you all,


That "foam rectangle" is the read-write magnetic head. Seems that it was somehow repaired?. I think that the calc works anyways without the card reader assembly. I think I tested that with my HP-67.


Thanks Alejandro. That's what I wanted to know.
The problem of the calculator is another one then, cause it's not only the card reader that's not working. And yes, when I received it it was clear it has been opened before so perhaps someone already tried to fix it.
Perhaps I'll try to send it to FIX-THAT-CALC ... although, with the customs problems I get to receive the unit back from repair, I don't know if it's a good idea cause I will at least have to pay import taxes to get it back I'm sure.



Step 1 remove the white foam.

Reconnect the wires, there are 5 connection points, 2 on the top side and 3 below.

Top left is red
Top right is yellow
Bottom left is blue
Bottom middle is black
Bottom right is orange

If you need more info, let me know.




Thanks a lot Ronald, that is what I wanted to know.
Although I believe the calculator is not working for other motives since that cable only affects the card reader and the calculator itself is not working.



Did you checked the internal voltages on the logic board. Tony Duel has documented the schematics and with that you might want to check the DC voltages to exclude any error's in that area.


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