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Calculator blog

Musings and comments about our common interest


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New springs for HP41c, Woodstock battery case

IMG_4321So far we have been using springs with 11 mm height, made in ss304 stainless steel, 0.5mm thickness, with the right size for the HP41c and woodstock battery cases. However, the height and spring effect proved to be too much in many cases: the pressure required to open the machines was too much. Also we had to sell them in pairs for the HP41, since very often our spring was taller than the one to be replaced.

In the picture besides you can see the old spring (at the back) and the new spring (at the front)

So we have taken off a turn in the spring and reduced the height to 8mm. It still works well but it forces less the calculator - in particular the fragile upper posts of the calculator.

By default we will serve these lower height springs, but we still have some longer springs if you abosolutely need them.

We will equip the battery holders with these too - it will make your calculator last longer. In the case of the Woodstock, this is very apparent - the previous ones were a quite tight fit.

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I have created a "HP15c Corner" in our website. Something tells me that it will be useful some time soon. For the time being, we will put there all the HP15c or HP15c LE that we get for sale, and all parts and accessories related to them, including leather cases, battery covers, etc.

We'll also take care of the links to this wonderful calculator that we may find, as well as all the software for it that was available at the time.


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More about: hp15c
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Classic charger

First finished prototype of AAA classic charger. Back and front pictures of the part. The mid battery is a tight fit since it has compression on both sides. We have not received yet the adhesive flexible circuit that will make the contacts, so we have substituted it for adhesive copper foil. There will only be electrical contact in the angled parts - the other contact will be masked in the flex circuit. I expect to receive in the next 15 days. I am optimistic about the piece. It will be a nice companion for all classic users. If you use rechargeables AAA batteries you will be able to recharge them outside your calculator!


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New HP Models

A Moravia officer posted a message in HP museum about new HP calculators, which in principle are new versions of the HP10bII+, HP12c, HP12c Platinum and HP17bII+. According to the company, these units are scheduled to appear closer to the end of the year - due to the semiconductor scarcity in China it would be impossible to have them sooner than that. No change in features - just new production models. One of the physical changes is a screw fixing the battery bay cover - and bigger battery bays in  some models. We'll give you more information as the moment arrives. There will be also other product introductions - and that may be interesting for the HP calculator lover.

Here are pictures of these new models:







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Classic AAA charger

The initial prototypes were done with adhesive copper tape. In order to do something prodessional, we will have to design something with a flexible PC, which we have created and asent to our PCB factory in China. Let's see what the price is, before deciding to go for it.


Herer are some more pictures of the prototypes:



If the process goes well enough, the following should be the battery for HP printers, HP)2/97, tape reader, etc.They will use the same principle, with a different design, of course

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Battery bay for classic calculators

We have received the first samples of the battery adaptor for classic calculators. It will have three AAA batteries that can be easily changed. It will require a couple of flex circuits to ensure the connections with the calculator. Most likely the circuits will be secured with screws - a minimum of 8 screws I foresee.

Here is a picture of how it looks like:


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HP12c is back II


Here we have a box opening of the new HP12c batch. It is made in the Philippines, not China. And it looks very good!


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More about: HP12c
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HP12c is back


The HP12c has been absent in Europe, Africa and Middle East distribution since at least 3 years ago. The HP management at the time could not comprehend that someone could prefer the HP12C (the one in "gold") vs the HP12c Platinum. The latter has 4 times the program memory of the former; can do more cashflows and has a double entry mode: algebraic and RPN. It also has a backspace key, something I miss a lot in the 12c (and which cleverly was included in the more advanced HP15c). The HP12c, on the other hand, is now several times faster, has a much more elegant color scheme (without the garish bright blue and red-orange colors), and has nicer screen characters (less stretched than the Platinum's). So they decided that with a single stock item they could cover both bases.

I have seen that there are many more HP12c users than Platinum's. Many financial guys are just accustomed to the 12c and would not change it for anything else. My former boss has a quite early unit that has been with him forever. He doesn't remember when he changed batteries last time. There are many that just want his trusty tool again and again - when they lose it or it is stolen from them.

Let's take a look at them, shall we? so that you can appreciate the keyboard color schemes and the screen characters. You can see the timeless taste of the original HP12c, compared with the bright colors, made for daltonic users, with the newer HP logo, of theHP12c Platinum


By the way: we think that both deserve our new leather covers over the ones supplied nowadays: Brown for the 12c, Bordeaux or black for the Platinum

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More about: HP12c
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Spice battery cover

I have been told that another typical problem with the Spice machines is that the battery cover breaks. At least two persons have asked me for a replacement of the original.

When you see the design, you see that there was a ongoing "theme" in HP design: the pricinples used in that battery cover were later used in the Voyager series (at a smaller size). Even the later voyager series (with the ARM processor) that had two CR2032 batteries shared the same design clues. There is a significnat difference: the spice cover has two feet glued in - so it has support function too. 

I started with HP by using a HP33c during my studies - until 1st course of engineering. The battery cover broke when the batteries grew in size after being in a drawer for several months. A pity!

Here are a couple of examples: observe the upper side. It is amazing that the Spice is so similar to both!


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Some things I did not know about the Spice battery holder

image1-48I created the HP Spice battery holder on request from Ignacio Sánchez. He is the person with the biggest HP calculator collection that I know. He told me that one of his problems is that he could not use his Spice collection. These were small machines produced at the end of the seventies that occupied the lower cost position in HP's calculator roster, replacing the Woodstock series. They had a nice form factor a keybaord, but they had some design issues. One of them was the battery. Once the original pack was damaged, leaked or broken, the problems would start. If you replaced it with AA-type batteries, these were a couple of milimeters longer than the original pack, putting an unwanted pressure on the terminals (that often broke) and the box (same). The consequence is that, in Ignacio's opinion, 80% of the world pospulation of HP Spices are now unusable, due to broken contacts, unavailable batteries, or broken bodies and back cover.

He gave me the idea of forgetting about AA batteries and replace them by the smaller AAA. To achieve the required length, we would use springs - the ones used in the HP 41c battery bay would do well. 

We did the design and it worked well. For Ignacio it was fantastic because he coulld use again his Spice collection, without having to resort to expensive refurbished battery packs.

What has surprised me is that this is general feeling among the customers. It is probably the product we have created that -pgives more happiness: it allows our customers to use calculators that they had not used for a very long time!

But we also have learned a couple of other things. In the original calculator, electrical contact was assured due to a small spring effect on the connectors. If this connector was broken, the spring action was lost and the calculator would not make constant connection, makiing it unusable. But in our part, spring effect is provided by our own springs located into the battery bay, so it effectively makes possuble to use Spice units with the contacts broken - no need to repair them! This was unexpected and it is a bonus for the purchaser - and in some cases saven him an expensive repair: see the comments we have received in the customer valuation for that product.

So, a product we had created just based on solving a single a technical issue is resolving more problems than originally expected; and apparently is opening a door that was closed before, enabling the use of some calculators that were in their drawer for many years. 

Comments like the ones our customers posted is what makes me tick!

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