HP 9100B


We have a HP 9100B here at my work in the School of Surveying at the University of Otago, Dunedin, New Zealand. We are looking at disposing of it as we have not used it in a very long time, would it be best to list it on something like ebay? We came very close to throwing it away with the rubbish but realised it could be a rather rare example just in time.

Any suggestions welcomed.

Mark Peters


Throw it away... use my trashcan. One in good shape should fetch a couple thousand dollars, give or take.


Be prepared for a lot of responses!

Although I get the sense that the 9100A has a much greater value to collectors since it is the first HP calculator. Look here for come analysis of HP calculator prices on Ebay. The chart doesn't make any distinction between 9100A and B:



Funny you should mention that -- I just started a disposal service for old HP 9100s. ;^)

Actually, as David Smith said, they do fetch a rather good price on eBay, but I'm sure that you'd be able to find plenty of takers here who would be willing to give it a nice home. Any idea how much you'd want for it?


Just one precaution, if you do end up shipping your 9100B from New Zealand: Please pack it very carefully!

There has been more than one report of 9100's arriving with broken CRTs from shipping. The CRTs were a custom part, and I think are irreplacable except from another HP 9100.

So, pack it carefully with ample and suitable cushioning.

Also, give a search around for any extra documentation, peripherals, or cords. They are sometimes harder to find than the calculator, and it would be an equal shame to toss them into the rubbish.


I would HIGHLY recommend double boxing it with good padding between the boxes. Actually the machines are pretty bulletproof (many stores of the falling off tables and being washed down the side of mountains, etc) and about the only real damage that can occur is that broken CRT... but you know how creative the Parcel Smashers can be.

Also the 9100B appears to be around 4 times rarer than the 9100A, but most collectors don't seem to really care. They both seem to fetch the same amounts.


I would guess the ferrite cores (both in the core-on-a-rope microcode ROM and in the read/write core memory) are brittle (ferrite cores normally are), but I've seen one get broken. I guess they're just properly supported. The light bulbs (to illuminate the register display labels, and for the error indicator) are also fragile, but they're easy to replace. The rest of the machine (apart from the CRT) is _very_ solid.
The CRT is delicate. Not only can the envelope fracture, but also the electron gun is assembled using brittle glaass support rods (inside the CRT envelope). I am told that if these fracture, you can get inter-electrode shorts in the CRT which will damage componets on the deflection boards and on the gating board (and if you're unlucky, on the flip-flop board as well).
Therefore, before powering up an unknown 9100 (particularly one that's been shipped), I'd want to remove the CRT (it's not hard to do), then take off the mu-metal can, and look at the electron gun just to make sure that nothing is broken or shorted.
Incidentally, I've managed to find 2 off 9100Bs and not a single 9100A so far, so for me the 9100B is much the more common machine.

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