My HP-35 calculator died

When I went to college in the fall of ‘73 they were teaching engineering students like me how to use slide rules. But the HP-35 scientific calculator had been introduced in 1972 and a few other students had them. It was an amazing thing. The HP web page (linked above) says:

HP asked a local market research firm to do a market study. They did and determined that the HP-35 Scientific Calculator would never sell because it was too expensive. Bill said “We’re going to go ahead anyway.” The product was so popular that HP couldn’t make them fast enough.

Bill remembered, “We figured, in the first year, if we could sell 10,000 calculators, we’d break even. We sold 100,000.”

I played with one for a little bit and then went to the University Book Store and bought one. It cost $300. That was a lot of money then. An entire year of school with books, tuition, room, and board was on the order of $2000.

I brought it back to my dorm room and the engineer across the hall from me came over and we played with it until dawn. It was absolutely amazing.

I eventually owned several different HP calculators. I programmed them and spent a lot of time “crunching numbers” for my electrical engineering problems.

I had gotten at least two different battery packs in the late seventies for my ‘35 when the old NiCads died and then ran it on the charger for years. The power switch got a little flakey and some of the keys got some bounce in them and I would have to sometimes fiddle with it to get it to work right. But it always would come through for me.

My HP-35 sat on the shelf a lot after I got newer calculators but when I set up my reloading bench back in the mid ‘90s I got it out and left it there. I would use it for estimating how many rounds I could get from a pound of powder or muzzle velocities and “power factors” from alternate powder charges or bullet weights.

As I was unpacking my gun room today I plugged it in and it would not turn on. I don’t know if it is the power supply, the power switch, or something else. It doesn’t really matter at this point. As of last month I have had it for 40 years.

I have another HP calculator I’ll put on my bench. If it lasts 40 years from when I bought it then it should last for at least another 10.



11 thoughts on “My HP-35 calculator died

  1. I had the TI-10 in 72, when “they” gave us the ok we could use it in exams… then later an HP 11c… still have that baby in my breif case… i also have the 11c app on my iphone.. you might want to check there for you replacement.. cant live without RPN!

  2. better yet.. you can get an hp-45 app, the 35’s big brother on steroids from 1973!

  3. 80085 and 7734

    First time I saw those on a calculator, around 1975, I just didn’t get it.

  4. I bought a used 25c when I went to college in 1976. Used it for years. The battery packs crapped out after a few years, so I ran it off the charger. I was ready to chuck it, but on a whim stuck it on E-Bay. A collector bidded it up to about $250. Sold!

  5. When I pull out my HP-41, I remind the newer engineers that it is older than they are, and still works fine.

    In HS I went through I do not know how many TI-30’s. First the LED, and then the LCD display models. The keyboards would get flakey, usually the 5 key was what gave out first. Or the LCD display broke (oops).

    • Yup, still got my HP-41CX, with the Thermal and Math packs. Good old size “N” batteries. Took a while to figure out the RPN, but once I did I liked it a lot more than things with an “=”.

  6. SPQR –
    First the bean counters took over and then they brouht in a female CEO, heh, heh,heh.

  7. Here’s a trick you can try if nothing else works. Pull the charger line off, and then remove the battery pack. Use a wire or paper clip to short between the two battery terminals, and then try putting it back together and turn it on. It’s a last-ditch try to clear the system.

    My old HP-25 was inherited from my brother, and I lost it in a fire back in ’83. My 11C is still sitting here on my desk at work. Scarred, scratched, and the LCD window is getting hard to view, but still the best piece of equipment ever made.

  8. I’ve always been a big fan of RPN. The 41C was the least well built of the HPs I owned. It was an incredible machine. The build quality, not so much. I get by today with a 42S and 12C.

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