Weird HP 97



I ended up with 2 HP 97s. Both work, and both print out nicely. However, one of them has a multi-color ribbon cable coming out of the back (through the same slot at the metal tab with the hole for a padlock/security device), that terminates in a DB-15 cable. Has anybody seen that before, or does anybody know if this is something the factory (or some part of HP) did?


P.S. Both units were from eBay.


That is an HP-97S "I/O Calculator." It's fairly scarce. Congratulations!

Museum page on the 97S.


Edit: scratch that. I should read the pages I link to before replying. Your machine doesn't seem to match what is described in the referenced article. I don't know what it is.


Edited: 17 July 2007, 10:35 p.m.


Do you have pictures?


Are they for sale? I want a 97. I have a HP45 in excellent condition.


I know that a number of HP 97s were modified by third party manufacturers as I/O units. I have two with pin connectors in place of the locking bar that were used to drive digital planimeters. For years I thought that was how all 97's were made until I started hanging around this forum :-)


I also know that at one time Mitutoyo use HP97s for some of their measuring instruments. They also used the HP85 as well.


I did look at the Museum's HP 97S link, and while entirely possible that this is a HP 97S, the cable in the Museum's pictures is a round cable with a grommet, the cable on the unit that I have is a flat multi-colored ribbon cable. The cable end (that is inside the calculator) shown in the Museum's interior view of the HP 97S looks like it could have the correct 15 wires, but the rest of the cable is different. Might be that this unit was originally shipped as a plain HP 97, but then the cable modification was added later on, making it simpler to run the ribbon cable out through the security tab slot, than to try to cut up the back of the case for the round white wire (although this is all just speculation). Might also be true that this was a third party modification, as well.

Either way, I will try to get some pictures tonight, but I don't really know how to post them, so I would appreciate any help in that regard.




Here are photos as promised. Sorry about the blurriness, but they should get the basic ideas across.

I'd still appreciate any ideas regarding this particular HP 97, or any other opinions. The unit is actually pretty awkward with this cable coming out of the back, so unless there is a reason to keep it this way, I will be having it removed when I send it in to Randy at

Hopefully, I did this right and the pictures are visible.


HP97 Overall view

Ribbon cable exiting the back of the HP97

Ribbon cable exiting back of HP 97, from top side

DB End of Ribbon cable

Edited: 19 July 2007, 10:27 a.m.


I think what you have there is a 97 modified to behave like a 97S. I have a similar beast myself, with a DIL14 connector and a ribbon cable leading to a second metal box under the calculator (looking quite professional) which carries the interface. I concluded that the 97 and 97S are basically identical, and that a 97 can be retrofitted to become a 97S, provided that the external interface electronics be connected. The nameplate of your machine, saying 97 instead of 97S, supports this claim. It would be interesting to know if somebody with schematics at hand could confirm.




I sent the same pictures to Randy of, and he says that he has seen other HP-97s with the same modification. According to Randy, the cable is basically parallelling the keyboard, simulating a key press, and was used in data collection applications.

I will be having the cable removed when I send the calculator in to Randy for the gummy wheel fix to the card reader, and some general TLC.


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