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I was having dinner with Pascal (a frequent contributor to this forum) in Interlaken, Switzerland last night (families included). When the time came to split the bill, we needed a calculator. His daughter was playing a game on my iPad. I borrowed it for a second, ran the HP-21 simulator, and gave it to Pascal. He smiled and did the calculations. Who said such machines are dead? Maybe just reincarnated!

Namir

I used the one on my desk frequently, but, alas, it is now placed on the shelf. I recently upgraded to an HP-25.

No luck running HP-21s and HP-25s using AA Alkaline batteries. They all end up frying some chip. So an HP-21 emulator for the iPad is splendid.

I also play with the Java-based HP-25 in this web site.

Namir

Really- That's terrible. I've never had a problem with alkalines or lithium cells (though 2 of my 3 19C's wouldn't power on after sitting awhile with lithium cells).

Do you think the chips were already close to failure? What do they show now?

Some HP-25 machines came showing signs of trouble and died. Some HP-25 came ok and then also died. The last HP-21 I got was working very well with alkaline batteries. I may have forgotten to turn it off one day and that's when trouble struck. I will not power up anymore.

I stopped buying HP-25s because of the trouble I had. I was more sure of the 21. Not anymore. Now I only have the iPad emulator.

Namir

Edited: 25 May 2010, 3:05 a.m.

I use NiMH batteries in my HP-25 -- no trouble so far, although I should probably mention that I don't use it often, it spends most of its time in a drawer.


Still, I always wonder why people would put alkaline batteries in calculators that were designed for NiCd batteries that deliver a significantly lower voltage. Applying 3V to a device that was designed for 2.5V seems like asking for trouble.