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Calculator blog

Musings and comments about our common interest


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Battery pack for HP printers and HP92, HP97 machines


By now, all original batteries made for Tomcat machines and HP41c printers cannot hold a charge anymore. There are several replacements in the market, all of them using the ubiquitous Sub C batteries, in different energy capacities. These batteries are cheap, and most of the packs are held in place by some rubber foam corners and adhesive film. You can find them in eBay mainly. 

I have tried to break apart two one of the original batteries that I have, to refurbish the original cells for new, current cells, but it was impossible without doing a lot of damage. This cannot be the right way to do more than one of them, and forget about series production! So we decided to make our own case

We have designed a two-halves case for these batteries, with precise holes for the connectors, to be 3D printed. Here the main challlenge is the cost of the parts in any 3D provider: it is far too expensive and it eats most of the cost. The parts are clipped one onto the other - and like the original, it is a single part used for both sides. We have not decided yet whether to offer it as a kit or send them fully assembled - I am quite frightened with batteries as opposed to passive, non-energy storing parts. There would be some soldering involved, in order to connect the cells among them and to the terminals.

There may be still some work to do in optimizing the part to reduce material - I can see a couple of areas where material can be taken out. However is the sheer size of the piece that determines most of the cost, I think.

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First run of Voyager cases finished!

Apparently there was demand for a true leather Voyager case. All the initial production run is gone. We have ordered a second run, which includes brown and Bourdeaux colors. 

image6The new colors are made of the same leather quality - just a different tint. 

If this is again successful, we will try with other models. The first that comes to mind is the Pioneer line: very similar design (but we need to take into account the slight wedge shape) and similar size. 

Other models are more complex - compared with the Pioneer or Voyager. If you look at one of them, it has several separate pieces, zippers and other parts that make them considerably more difficult to produce - and substantially more costly too. Probably it will not make too much sense to sell it if the price is too high. However, second hand cases like HP41c's command extremely high prices - like 40 dollars in some cases!

As we have explained, we also have ordered new sponges for the HP41 case

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Different colors for the Voyager true leather cases

We have just ordered from our supplier two new more colors for the leather cases. 

Up to now, we have been selling the black case. I think that the quality is really excellent and the first batch is nearly gone. We have ordered a second batch - and also the two new colors: Brown and Bordeaux (which would be called Burgundy elsewhere). The pictures of the two colors that I have do not make justice to the real aspect - I will post them once the first batch has arrived.


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The HP12c "Gold" is back !!!


We have found a stack of English language HP12c - the one with gold color, RPN only, and much faster than the platinum, with a ARM processor! (what was called at the time HP12c+) Nicer screen too.

We will offer it with and without leather case - for 89.90€ and 77.00€ respectively. (all units come with the standard fake-leather PE case anyway). Order before units disappear !!


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More about: hp12c+
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Good things coming next year!


Next year is the 50th anniversary of the seminal HP35 calculator - the unit that started it all .

It is quite likely that there will be "something" from the licencees to commemorate this fact. From what I understand and heard, I think we all are going to like it!

(it will not be a reissue of the HP35 - which is a beautiful unit but not a practical calculator to be released!)

Let's be ambitious!

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More about the leather case for voyagers

I have sent the first lot of Voyager cases to customers. Trust me: the look wonderful ,and have the leather texture of the original vinyl cases!!



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Navigation Pac

We have found a unit of Navigation Pac. This time we have found the manual too!

There was a time when many pilots crossed the world with a HP41 with either the navigation pac or their own software. Among them, Geoff Quickfall, Air Canada pilot and the person that knows most about repairing HP calculators in the world!

The pac and manual include the following routines:

  • Course planning programs - including the great-circle calculations
  • Celestial navigation programs, including all included stars and planets used in the Nautical Almanac.
  • Other subroutines including calendar functions, coordinate conversions, etc.


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Spaces for repair

tipops_de_traserasEarlier HP41 full-nuts fixed their processors to the keyboard circuit by means of nuts screwed around the screw posts. The screwing allowed it to press the processor through the zebra to the keyboard circuit. The back side of thecalculator was designed that way: there was a flat side on the underside of the screw posts - see right side of the picture.

Later in production, someone decided that these nuts could ve spared by building a couple of spacers in the back side. These spacers would pass the pressure onto the circuit. You can see them in the left side of the picture. 

The problem with this approach is that it made the tension od the screws fundamental for the proper working of the machine. With the screw posts under tension, there were more and more failures as they broke more often. Also, with the original design, the pressure in the lower part of the case was not required for proper operation - only the upper part needed to be secured.

But the first approach (the "nutted" one) was not free from problems either. You could unscrew it once, to make a repair; but it was very difficult to screw it back on the post. If you had to screw it and unscrew it a couple of times, you broke the screw post completely!

So we decided to replicate the newer back on the older back, by putting aspacer, initially glued to the back side. That had a problem: which size of spacer? there are different thicknesses of circuits, the earlier being thicker than the latter.












Then we realized we did not need to glue it: it was enough to lay it on the circuit, and we could produce it in a variety of thicknesses and we could use whichever fitted best in each case:


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HHP Eprom programmer in card reader case

A customer of us has a Hand Held Products EPROM programmer in a card reader case for the HP41c family - anyone has information about it? Manuals, etc? Probably it can do functions that some of the Diego Diaz products can; but without a manual, we're lost! 




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News from Moravia


I spent some time the other day with a Moravia exacutive, talking about the current and future plans regarding HP calculators. As you may already know, from November 1 HP has licensed the calculator business to Royal (for the Americas) and Moravia (for EMEA and Asia). There are many things that cannot be said, but there are several things standing out.

- It seems that the licensees will move faster than HP - there are less layers of bureaucracy, and these guys have been many years in the industry.

- There is a team that will continue the development of the HP Prime - which is a very good calculator.

- The licensees (who have been distributing the HP brand for many years) know the many recent flops of HP product: the quality issues, etc. On the other hand, they are very much business driven - and therefore they have a clear view of the market and are less "romantic" than we are. Their product plans, however, will have "something" for us all.

- The semiconductor scarcity is impacting on the bringing back to market of some models.

As soon as I have a confirmation on the definitive line-up I will come back to you guys with the information!

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