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The 28C was my first HP. I sold that and later acquired the 28S. It is still my favourite. I used it regularly up to about 5 years ago due to a broken battery door. Indeed, it was dropping it that broke the door & surrounding case. I now have 3 28S's, one mint in box, two with broken battery doors. I now use a 35s and a 50g as my daily calculators, I don't want to risk more damage to the 28's.


I had my first-buyer HP28S stolen more than ten years ago. I bought two others - eight and five years ago -, both in very good operating and cosmetic condition, but one of them has some small fissures in the surrounding case of the battery door. Anyway, none of the two had the same operating characteristics as the first one, bought NIB. The later HP19BII offered a better solution for the battery compartment and door, too bad the first Clamshell were not that way.

The HP28S was not one of my first HP calculators: I had one HP41C, one HP41CV, one HP41CX (and some extra add-ons), one HP15C and one HP16C at that time. Apart of comms and regular time resources, I could do everything I needed from the others with the sole HP28S. And much more.

Great little beast. The very grand-grandmother of the new graphic ones.


Luiz (Brazil)

Edited: 27 Feb 2012, 2:59 p.m.

The HP-28S is also my favourite calculator. When I first got mine in the late 1980s I remember thinking how having a pocket calculator that could manipulate and solve equations symbolically was like something out a science fiction movie --- a qualitative leap forward. The structured programming with LISP style features meant I could use the device for prototyping high-level code on the train, in a cafe ... anywhere. It also made a nice matching set with the recently discontinued HP Infrared printer which I found useful for reading and preserving longer programs.

I have found that Loctite Gel glue carefully applied inside has sealed and strengthened fractures that appeared around the battery compartment. So far, the repair has lasted around 6 years and it is barely visible. It is a pity that replacing the back of the case with one from the later HP-19Bii, with the revised battery cover, is not really feasible. Though I would like to see if someone has tried this as an experiment.


With a 35 red dot, 21, 67, 12C, 15C, 41C, and 41CX in my HP stable, I was a early purchaser of the 28C in 1987. It seemed to have potential, but I found it wasn't near ready for prime time. The absurdly small amount of RAM made it useless except for the trivial. Twice a fool, in 1988 I was an early purchaser of the 28S. It turned out that the 28C/S needed a lot more than just memory to be tolerable for any real uses. At least I still had the 15C and 41CX for real work. I had not realized that by 1988, the real gem in the HP line was the HP-42S that HP failed to market competently, no doubt aware it could crush the RPL gimmicks that were being presented (ultimately without success) as "wave of the future". In my electrical engineering career from 1974 to 2011, I personally don't know of any real ad hoc engineering problem whose solution was aided by symbolic calculus on a pocket calculator. I suspect no one does.

I'll say that I like the 28S better than other nonsense like the 38G. Insanity ruled at HP in the 28C to 49G era.

No complain about "left-coast artsy", ugly color schemes this time, Mike?;-)

Eh eh eh...sorry, couldn't resist!


Mike wrote:

At least I still had the 15C and 41CX for real work.

I bought a few HP15c LE calculators which are nice handy devices that I use daily, but I find it much faster to first prototype my code in a readable software package such as R and then reimplement it using RPN keycodes rather than struggle with the single line numeric display. With the HP28s I could just work out problems directly on the calculator, porting the approach used later to the static computer at my workplace if needed.


Edited: 29 Feb 2012, 3:39 a.m.