Ernst Mulder's Calculator Museum

About this Calculator Museum

One of my stranger hobbies is collecting calculators. I especially like programmable calculators, and of those I love the ones made by Hewlett Packard the most.

This hobby started somewhere in the late seventies. I was already very much interested in calculators (see below) when a friend of mine (hello Arno Maas) discovered that a local retailer (the now defunct V&D retailer) sold broken calculators for about $1.50 to $10. They would normally throw them away but if you asked nicely they would sell them cheaply.

That’s when it really started. Those broken calculators were usually very easy to repair, a cracked print-track, a loose battery contact, a broken on/off switch - those were usually the problems. Some "broken" calculators simply had flat batteries!

Later I was able to buy some of the calculators new, and sometimes people would donate me their old calculators. So if you want to see your old calculator in this Calculator Museum - I’m your man! :-)

Today producing a four function calculator is evidently quite easy, you can buy a standard calculator for about $1.50. I’ve got the feeling that more work was put in the older calculators resulting in better products and accompanying peripherals. Today’s super programmable calculators may have a abundance of functions and options, but also are quite difficult to use, have interface problems and other issues. Moreover, the product expected life-time of modern calculators is probably much shorter too. There are exceptions however. And of course we nowadays have smartphones.

Speaking of smartphones, they are of course a kind of last "nail into the coffin" of old fashioned Pocket Computers and other calculators, but they are aslo a blessing, because nowadays they can emulate really accurately many of the older calculators. Many of them are of course installed on my own iPhone.

What do I collect?

There are a lot of calculators in this world and I can not collect them all. Therefore I’ve tried to find a subset that suits me. Therefore I’ve decided that I collect calculators that can run on battery (or solar) power. I therefore do not collect mechanical or mains powered calculators. Except for some of the older HP’s which are so extremely beautiful. So, I try to collect ALL HP calculators and any other battery or solar powered calculators I can find. And I generally prefer older calculators but there are of course exceptions.

Some remarks

The very first calculator I have ever touched is still in my possession. My father bought it on one of his visits to the US of A when I was about ten years old. It is the realtone Model 8414.

The second calculator in my life is still used by my father!

The first calculator I ever owned was given to me by a friend of my father, and is probably the one that started it all. It was the TRIUMPH 81C. My original 81C doesn’t work anymore but I put it on display in this on-line museum anyway. Thank you Theo van de Ros, you ignited a spark, not only in loving calculators but also in loving electronics and engineering. And for introducing me to the Stirling Engine.

The first calculator I ever bought myself was the TI 30. That was when I was about 12 years old (1977). Well, actually that was the second one I bought, I had bought a four-function model myself, and when I showed it to my father he said I should bring it back and get a "real" calculator. The calculator I bought had a "flaw" (√-9 = -3) which was enough to get my money back. He then tried to explain all the scientific functions to me but I didn’t quite understand them!

My most favourite calculator designs are the HP 15C, and the HP 41CV. The most usable programmable calculator ever, in my opinion, is the CASIO FX-602P (I’m not including the basic programmable pocket-computers).

My most favourite Pocket Computer has to be the TRS‑80 PC‑2. The reason for that is that I spent a great many hours learning about this device and discovering how to extend its BASIC command set using my own machine code.

And my reward for the best school calculator goes (with praise) to the CASIO fx-82MS.

My reward for the worst keyboard layouts goes to joined winners TI 68 and the CASIO fx-5000F.

When I get a new calculator I first examine whether it’s still fully operational. If necessary and possible I repair it. Then the calculator is thoroughly cleaned. Except for a few (two, so far) exceptions, all calculators in my collection are fully functional. The calculators’ pictures are taken by scanning the calculator using an old HP ScanJet SCSI scanner (see the Resent changes page). All pictures are therefore scanned using the same type of scanner and resolution settings of 150 DPI (safeguarding the pictures’ relative proportions). All calculator pictures were retouched to remove dust spots and scratches and such. The 150 DPI resolution was one I chose when I started this site long ago but so far it still seems to suffice.

For those looking for manuals, I hardly have any, so please don’t ask for copies. Today the best place to look for calculators are flea markets, and most of them sell their calculators without manuals and such. If you’re looking for HP manuals, try hpmuseum.org (link valid 2024-01-13).

Many other manuals can be found using Google or by visiting sites of other calculator collectors. The manuals of a number of Pocket Computers can be found on PockeMul’s website pockemul.com (link valid 2024-01-13).

Please email me if you’ve got a calculator you are about to throw away. Or want to simply show to the publik. I’d be delighted to add it to my collection. Anyone donating a calculator can get their name referenced on the calculator’s webpage, it they want.