Calculator blog

Musings and comments about our common interest


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Repairing the rusting battery bay of HP41c.

You may have bought an HP-41 in EBay, just to find that the battery bay is utterly rusted. There goes your investment! Maybe you wanted it for CL conversion - maybe it was your first 41c and you wanted to see what’s all the fuss about it!

Whatever the reason, letting the rust inside your calculator is a recipe for later disaster. It will corrode the circuit lines, communicate to other parts of the circuit, destroying your investment (and, in the case of the CL, it IS an investment!)

You can easily buy port covers, even battery cover; but it is much more difficult to find this piece in internet. And with a good reason: it is the first thing that fails in the HP41c, and therefore you can only salvage the other parts.

Well, there is an option: you can buy in our shop the adhesive circuit that adapts to the plastic body of the battery connector. It has an extremely strong bonding, and the shape is perfect for the task. I have to say that it is a little difficult to put it properly: you need a firm hand and some experience to do it. I would not recommend to buy one to repair your only calculator, since it will not work properly the first time. At least it did not work for me the first time, but I got the experience of what failed. The second time went well already. So, my advice is: if you want to repair just one calculator, you’ll be better off buying two. If you’re repairing more, then n+1 - so that you can afford one error. Or you may be more skilled than me - in than case buy just as many units as repairs you need to do.

The circuit comes with clear repair instructions, but I would stress the fact that you need to bend it properly to shape beforehand, using the guidelines, and that you should start in the cavity between both ports.

I have used it to repair a calculator that would not start, and that I bought in internet as “for parts”. Now it is my CL. Today I have just repaired a non-working CV - this time keeping the original board in. This will end up in another CL as soon as I receive the new boards, with Sandmath 2x2, among other new features.

Please take a look at the beautiful finish of the battery once repaired.




You can find it here.

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Calculators for the Iphone 5

i41cx review

My former telephone died and my wife got me an iPhone 5. Then I set to get some calculators to work with in the system. In particular, I downloaded all the free ones. Here's what I got:

I did not load the HP15c in any of its versions, since i always carry one with me. I find that it is the finest device ever made for personal calculations, only rivaled by the mighty HP42s - but this is a completely different discussion...
I took the free version of the HP42s, Free42. It is built for the smaller screen of the previous iPhone versions

I got RPN25 calc. When you need a simple, RPN calculator, this is a nice alternative, since there are not too many keys and it has the basic set of functions. Also for smaller screens, but it is a pleasure to use.

I got a very simple RPN calc, iRPN Calc, which is as simple a calculator as you may find anywhere, with a very nice twist: you can change the items in the stack by moving them around with your fingers. Also for smaller screen.


I48. not built for the iPhone 5 - there is a wide white band in the lower part of the screen - it is in need of an adaption or at least a recompiling, in order to be livable with in the iPhone 5.

PowerOne SL: does not try to mimic the original HP calculators, and it is the first one that does fill the whole screen. It opens as an algebraic model, but when going to the settings page, you can change it into RPN. It has several pages for different functions, from numbers, angle functions, other transcendental functions, and memory registers. This is a fine addition to the screen.


The i41CX+

One of the calculators that has marked my scientific life was the HP41cv. This was a machine that offered a young engineer the promise of doing anything - from controlling peripherals to all kinds of calculators. I have been following with attention the HP41cl developments, and I find extremely interesting the old, loved 41c body with throughly modern innards - and sometime I will get one. But it just does not fit in my pocket.

Therefore I took the plunge and download the full version i41CX+, with CAS. Let me state first that I have not been able to delve into the CAS, since I have been exploring the different modules available (the CAS is one of them). It works basically as the original one, and it has been adapted to the longer screen of the iPhone 5. Lest I forget, it is not free, but close to 25 € (once bought, you cannot see the price in the store). Let me say that it fully justifies the purchase.