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Calculator blog

Musings and comments about our common interest


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Corrosion on battery contacts


The assembled repair kit is a drop-in part for damaged-corroded battery contacts in the hp41c family of advanced scientific calculators. It solves the main issue that plagues old 41c units.

There is a cheap alternative when the damage is minimal. There are times when there is not too much corrosion, or where friction has caused the black support to appear (meaning the metal has disappeared in the contact area, but it is still available around). In these cases, there are two material that you need to know: Caig De-Oxit and the adhesive Aluminium paper.

Caig is an American company that produces several liquids to clean metals. I have been using its compounds for my hi-fi hobby for a long time - the sound and image really improve when you clean the interconnect contacts with De-Oxit; and they are maintained in good condition (and the golden or nickeled contacts preserved from dendritic corrosion) with Caig Pro-Gold.

Well, Caig De-Oxit works magic for removing corrosion. Use it with cotton sticks, rub them gently on the corroded part and you will see how the corrosion dissolves.

I have been using it recently on several deep corrosion cases on hp41c. Not only the battery assembly was corroded beyond repair, but also the circuit lines were completely green. As the battery assembly circuit had been destroyed by corrosion, the only solution there was the repair kit; but for the main calculator circuit, a generous application of De-Oxit led to a completely clean machine that worked from the first second it was reconnected. I must say that I have also failed with other calculators, but that may be due to additional damage elsewhere.

Tomorrow I will show to you the adhesive conductive film


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New HP41c repair kits!

We have received a new shipment of repair kits and we're going to produce the assembled repair kits off them. 

What is an assembled repair kit? As we know that many of you (myself included) have fear of folding and adhering the flexible repair kit to an old, damaged battery plastic body, Nacho does for us. So far, it consumes a damaged old battery body - so it has to be taken from calculator bodies damaged beyond repair.

Hopefully one day I will set myself to create a 3D body that can be used for the purpose - but I haven't got the time so far. T

he assembled repair kit is a drop-in part for damaged-corroded battery contacts in the hp41c family of advanced scientific calculators. It solves the main issue that plagues old 41c units.

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Más sobre: HP41c
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HP Prime iOS app!!

HP has just issued the HP Prime app for iPhone and iPad! It works fast. There are several minor bugs, but that's to expect, since the new appel guidelines imply that the code had to be converted to 64 bit from 32, and that all characters are stored with 32 bits (which allow much more complex character sets).

The app can be found in the App store. Be aware that there was a version for Android since several months ago.

You have here a demo of the app:



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Más sobre: HP prime, app, iOS
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News for HP41CL users

Some of the users of HP41CL bought it with serial interface. They did it in order to be able to load new modules, I guess that many of them never did - it was too risky if you didn’t have the right instructions. At least this was my case - other users might have bee more experienced or daring.

Well, Monte Dalrymple has prepared a guide for the updating of modules in your calculator. You can find it here:

I have not tried it, but I plan to do it during these holidays. But for you users, it may be of help.

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offers for Black Friday - 3


4509629This is a calculator that was designed for China. Based in the same hardware-software platform as the HP Prime, and running the same HPBasic language (albeit with some less functions), this is a very powerful calculator. The main differences firmware-wise with the HP Prime is its lack of PRN entry method, and the lack of CAS. In the hardware side, it has very sharp screen with 16 grey levels, and a set of batteries run on parallel: yes, you can even run it with a single battery, but it won't last long that way!
And, at the special price of 50€ during Black Friday, it is a fantastic opportunity for a collector that wants to have the complete HP set.
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Offers for Black Friday - 2

DSC_7897_LSince the HP42s, then has not been any significant development in Scientific calculators, at least in the RPN flavor. When HP released the HP30b calculator, it provided also a Software Development Kit with it. The machine used a well known third party chipset, and had a Pogo connector for upgrading software. Some aficionados saw the opportunity of creating the best RPN calculator ever.
It has all the mathematical functions you can imagine, and then some; it can have a 4 or 8 level stack; and it has many constants you can use in your equations. And, of course, it is programmable.
We install the latest version of the WP34s firmware on a brand new HP30b calculator;and we supply an adhesive overlay with it (we have found that customers prefer to collate the key labels themselves. We have reduced the price from 94€ to 75€ for our Black Friday.
Only three available.

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Más sobre: wp34s
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Offers for Black Friday - 1

Now that Christmas is close, it is the time to think about gifts for others - and for yourself. You can recall your youth, and the time when you were longing for an HP41c, and you had to settle with a lower choice; or you could afford it, but not the wealth of modules and options; or you had it, and got it lost, stolen or damaged beyond repair. Now you have the opportunity of having it back!
With a new processor, totally compatible with the original Coconut CPU but 50 times faster, having burned in its memory the contents of all known program modules and then some invented by today's programmers, and carefully assembled on pristine bodies without corrosion or screen damage, you can now buy the HP41CL from
  • 50 x speed compared with the original; Switchable to several speeds including the 1:1 original.
  • All known software modules of that time
  • Many new modules designed lately, including the Sandmath family, an HP16c emulator, complex numbers, advanced matrix, etc.
  • All the addressable memory of the original
  • Additional flash memory where you can download and write new modules.
  • Possibility of a serial module to download new modules and capabilities from your PC
  • Compatibility with all external modules and interfaces (time module, infrared module, printers, barcode readers, interfaces, etc.
Pricing: usually 625€; 550€ during the Black Friday period, and 625€ if we include a time module with manual. For more options, please look in our website

Limited to 4 units only.
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Comments on HP41CL troubleshooting

The users of the hp41c machines need to be careful while taking their calculators on a trip. The machine is sensitive to vibrations, and doesn’t have as big a capacitor as the original one (which could allow you to change batteries taking your sweet time, and all the programs and configuration would still remain). It has happened already a couple of times that a calculator sent has lost its configuration, or even wouldn’t start.

We reviewed the case in this blog issue, but we think it is relevant - when you buy such a expensive calculator, you need to be sure to be able to revive it when it has a hiccup!

The question comes then on how to initialize the calculator. There are different possible initializations, but in have to confess that this is beyond my knowledge. The only thing that I want to make sure of, is that library #4 is installed in page #4. This library comprises several subroutines that are used by a number of modules programmed and/or compiled by Angel Martin. Basically these are the sole modules being developed today, and include an interesting clone of the hp16c, the extremely powerful Sandmath modules (which turn the hp41 into a very powerful mathematical machine), the advanced matrix ROM, the Complex Functions ROM, the matrix/polynomial ROM and other operating systems and toolbox-oriented ROMs. The interesting thing is that it doesn’t use any of the typical ports, so you are free to use all your modules (also taking into account that, if you plug in the real Time module, it doesn’t occupy the corresponding pages since its functions are already in memory in the hp 41cl)

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CHOOSE() menu function for HP Prime

Two blog issues ago, we discussed the screen menu and how to make it work. We had to descend to pixel level programming. It is still far from low level, but it is considerably lower than anything done before. This is what “tab menus” entail.

There is a different (and simpler) way of choosing between different alternatives: the CHOOSE() command. Let’s see an example:

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Mac Prime Emulator

I am trying to get the HP Prime to work in my mac - again. I have Windows Parallels running XP, and it worked well until the last two firmware versions, where it doesn’t work anymore. I'va been told that I need Windows 7 at least.

There is a HP Prime emulator in internet for MAC. It is based on wine, and you can find it here:

However, it comes with firmware 5447 - a few moons before! It doesn’t have most of the features that we now love about the Prime.

When you try to update the firmware from within the app, it does find a new firmware in the hp servers, it connects to it and downloads it; but when it finishes downloading, it gets out of the app and nothing has been done.

The alternative is to buy Windows 10 (I can’t upgrade for free from XP - I need to have 7 or 8 at least to qualify for the free upgrade). And spending 120+ € for Windows when I have already a Windows PC at work hurts my Mac heart. So I will have to delve in the intricacies of Wine, in order to make it run properly. I understand that it has something to do with the installation of VC++ 2013 libraries, but I need to learn more. I would thank very much an of you that could help me in this ordeal!

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