Calculator blog

We have been closed from August 4 to August 19, but we're now delivering the last orders backlogged. By the way, we have just finished our stock of repair kits for the HP41, and we have just reordered; on the other hand, we have a couple of time modules available for sale, which will get a 30 € rebate if they are bought together with an HP41CL machine (of which we have two available right now).

Nice to hear from you again!!

We have sourced an original Time Module for the HP41C  available at 150 € plus shipping. If bought together with a HP41CL  he price is reduced by 30 € - please contact sales@thecalculatorstore.com to organize (there are two HP41CL left).

This time module comes with a user manual in French

There is as well a HP41CL based on version 3 of the circuit - it is sold at 470 €, with a discount of 140 € over the v4 (and latest) version.

Well, we sent the message yesterday and the first of the two calculators was gone. The one that remains is the tall keys one.

During this week end, I will assemble the other circuit into another calculator. Hopefully we will have the third one!

Meanwhile Monte told me that he’s ordered another set of 35. Already, 10 of them are gone too. The version is exactly the same as the previous one (v4), but it surprises us that the 41CL are going faster than expected, and, if anything, sales are accelerating.

If you have a HP 41c calculator and you want to have it thoroughly updated, you need to look into the HP41CL conversion. If you have some experience with electronics DIY, and you have the right (full nut) calculator, then by all means do it yourself. You will enjoy a good time, you will get a feeling of success and you will gain even more respect for the HP engineers that designed these machines to endure. Most of the telephones of today will not last as long as these calculators, that, after 30 years, are still going strong. And the CL conversion puts at your fingertips every known software module - you just need to put the module code in the alpha register, type PLUGX (where X is the port you want to put it in) and you’re good to go.

However, it may well happen that you don’t dare to risk your precious calculator. You have no repair experience and you feel you can’t do it. In that case, we do the conversion for you for 400 €, including the CL circuit, assembly and testing, 1 year guarantee and VAT included.

And finally, if you want to keep your calculator as it was, or you lost it many years ago and want another, but you don’t feel like buying again all the modules you wanted, you can order the full Monty from us (no pun intended!). The prices vary, depending on the options (serial port and serial cable, tall keys or not, the availability of a box, etc. You can find them here.

Please contact us at sales@thecalculatorstore.com for more information or special needs.

Two new HP41CL have just seen the light!

One is an early tall keys machine. It is serial number 200900017 (so 9th week of 1980, which makes it a quite early unit). It is the type with flat keyboard surface (as opposed to the textured keyboard surface that appeared later until the end). This flat surface is very much alike the one in prior HP calculators, like 45, etc. (35 was grey instead - later HP turned to black for a more attractive finish). The screen is grey, not yellowish, as it should be.

The other is still old, (serial number 2103A03403) but it is already a low keys, textured-keyboard unit. This one is probably the best calculator I have ever seen. The keyboard feel is the best I have the pleasure to work with, the screen is excellent too. I have installed on it the virtual modules advantage pac and Sandmath 4*4 (the latest iteration from Angel Martin, nonexistent in any but the most recent hp41cl cards.

As a comment for those who say that the prices are expensive: to get these two excellent calculators (plus one more still in the works) we actually bought 5 of them, but two of them didn’t reach the standard we have set for these modified calculators. One of them was a 1949A… Serial number, so you can imagine my sadness. And you know how much hp41c calculators cost in the usual places. Of course, you can always send yours to refit (well, now that would take some time since We have finished all the world stocks, once the last calculator has been assembled)

Our standard:

• Non corroded battery bay
• Good screen: all digit segments can be seen with equal streght.
• All port covers in good shape
• Clean keyboard. You wouldn’t believe what we have seen. Ignacio has spent hours on end to get some calculator back in shape - and he has failed sometimes, due to all the dirt present.
• Good keyboard feel. Usually, keys 1 and 2 may be a tad softer, but the click has to be clear and pleasurable in all of them

You can see a couple of pictures of the two new hp41cl calculators besides. Sorry for the bad lighting conditions, but the picture was taken on my desk late at night yesterday, when finishing them.

Please do not hesitate to send an email to jose@thecalculatorstore.com to enquire for specific options for you calculator.

With all the fuss about the spacecraft arriving to the proximity of Pluto, it occurred to me that it could be interesting to discuss programs for HP calculators that calculate planets orbits - so I set to search for that. And it found it from none other than Eddie’s Math and Calculator Blog. You have seen it mentioned here several times - he is able to treat a number of different subjects, always from interesting points of view, and from many different scientific areas.

The program he has created doesn’t only deal with Pluto, but with all other planets! It can calculate the speed and the distance from the sun at any given time from each planet’s perihelion (if you don’t remember what the perihelion is, a school refresher: it is the point of the orbit where it is closer to the sun (one of the two focus of the elipse)

Here are some orbital data from Pluto:

http://nssdc.gsfc.nasa.gov/planetary/factsheet/plutofact.html

And here is Eddie’s article:

http://edspi31415.blogspot.com.es/2015/06/hp-prime-orbital-speed-and-velocity.html

And, finally, here is the program:

EXPORT ORBSD()

BEGIN

// Orbital distance and

// speed around the Sun

// EWS 2015–06–25

// Initialization

LOCAL lm,pm,la,pa,le,pe;

LOCAL ld,pd;

LOCAL p,sp,θ,d,v,r;

// Planets

sp:={“Mercury”,”Venus”,”Earth”,

“Mars”,”Jupiter”,”Saturn”,

“Uranus”,”Neptune”,

“Pluto (Dwarf)”};

// Mass (kg)

lm:={3.29438ᴇ23,4.85749ᴇ24,

5.9722ᴇ24,6.40397ᴇ23,1.89469ᴇ27,

5.67312ᴇ26,8.66437ᴇ25,1.02224ᴇ26,

1.31ᴇ22};

// Semi-Major Axis (m)

la:={57909829824,108209876544,

149594962176,227921734656,

778412012083,1.42673ᴇ12,

2.87097ᴇ12,4.49825ᴇ12,

5.90637ᴇ12};

// Eccentricity (ε)

le:={.206,.007,.017,.093,.048,

.056,.046,.009,.249};

// Days in a year

ld:={87.96899,224.701,365.256,

686.98,4332.58899,10759.22,

30685.4,60189,90465};

// Input

INPUT({{p,sp},d},”Data”,

{“Planet:”,”# Days:”},

{“Planet”,”# Days after

Perihelion”});

pm:=lm[p];

pa:=la[p];

pe:=le[p];

pd:=ld[p];

θ:=360*d/pd;

HAngle:=1; // degree

// distance

r:=(pa(1-pe²))/(1+peCOS(θ));

// orbit distance

v:=√((1.9884ᴇ30+pm)6.63784ᴇ−11

(2/r–1/pa));

// output

PRINT();

PRINT(“Distance from the Sun:”);

PRINT(STRING®+” m”);

PRINT(“Orbital Speed:”);

PRINT(STRING(v)+” m/s”);

RETURN {r,v};

END;

Three ways of inverting a matrix in RPN.

Let’s assume in M1 we have a 3x3 matrix. I took this example from Khan academy:

0 2 2

1 1 1

0 2 0

How we can invert it in RPN. I know of three different ways. Please update me if you know of any other!

• The translated from algebraic or CAS:

M1         !to the stack with Enter

inv(1)     !to express that it’ll use a single argument

• The logic from HP’s history : using the X–1 exponent key

M1         !to the stack with Enter

X–1        !much shorter than the other - but you still need to press the blue f key.

• The other possible alternative: dividing 1 by M1, with the divide “/“ key

1          !ENTER

M1       !ENTER

/

The last two imply that the functions have different operation on different days types, and implies a CAS behind,or very good programming (let’s remember that the HP15c achieved routinely several of these feats, with its excellent use of all the keyboard keys for more than one function - and in some times 3 different functions, depending on the data it was operating on (number, complex or matrix) and how the “user” flag was set)

We usually get questions about repairing defective HP41c. It is usually Ignacio who repairs them, since he is much more knowledgeable than any other I know; but there are many repairs that can be performed by anyone of you - if you just dared to open the calculator. Let’s discuss the different cases, and tell what is difficult to repair from what is easy.

Rust in the battery contacts. This is one of the repairs that I would consider easy, and that can be done by any of you. Please refer to this product in the website​

Calculator would not start, but the battery contacts are OK. First check battery polarity. Second, is your calculator a full nut (square screen corners) or half nut (round screen corners). If full nut (meaning it has two circuits, pressed one agains the other by the two lower screws that are hidden by the rubber pieces. This is by far the most frequent problem, and it is called “broken lower posts”. These can be easily repaired by yourself (unless someone else tried before and destroyed the assembly). This is many times one of the most satisfactory repair: a little glue, a little time waiting for it to cure, assemble it back, and voilà - a previously lost calculator is back at work

Screen problems. It can be easy or difficult. If there is a black part of the screen, consider it difficult - you’ll have to get a donor for the screen, and the soldering and desoldering involved is not for the faint-hearted. If there is a blurred set of segments, it may suffice with cleaning the PCB and making sure that the circuit connects well to the main board - that may solve the issue.

Keyboard issues. Can be easy or difficult, but it is worth trying it yourself to check. There are different kind of issues: bad contacts and bad clicking action of the keys (some times can be cured with cleaning -easy- but other times the key dome is broken -difficult and a donor is required). In general, opening, cleaning and adjusting it is good practice and doesn’t damage anything.

Finally, if the repair didn’t work, or you feel you can’t do it yourself, you can always contact Ignacio through us: sales@thecalculatorstore.com

Here we’ll show to you an app for which probably the Prime was never intended - and for which many other tools (beginning with your telephone) are much better suited: a picture viewer.

The programmer has created an app that 1) works on the newest firmware (8151), 2) can make use of the pinch gestures to apply zoom to a picture, and 3) allows picture input through the connectivity app.

You can find it here:

http://www.hpmuseum.org/forum/thread–3895.html

I have also talked before about hpcalc.org. This is a fantastic site also devoted to HP calculators, mainly based on RPL models, but which also has a department for the new Prime. It has the following program areas:

• Documentation,
• Games,
• Graphics and Plotting,
• Math,
• Miscellaneous Applications,
• PC Programs,
• Programming Tools,
• Science Apps,
• Utilities

The whole can be found here

I have received a couple of questions regarding HP guarantees. You need to know that HP is offering a 1 year guarantee in general worldwide, but it is important to know that the guarantee applies only for the region you have bought the calculator. The world is divided in three regions: Americas, EAME (Europe, Africa and Middle East) and Asia.

This is intended to avoid "grey imports" whereby a company imports calculators from a cheaper place, in some cases circunventing the import duties. It is a nuisance, but this is the way it works!

Moreover, in EAME we have different versions for the groups of countries we have in Europe. Typically there is an English-French version, a German-Italian-French-Dutch, a Scandinavian version and a Portuguese-Spanish version. Primes come in an international version - again different from what is supplied in the Americas.

Typically, when there is a problem with your HP calculator, if it is a new model, there are basically no parts to repair. If it is less than one year since you bought it, you can call HP's support telephone. They will go with you through a number of questions, but most likely at the end they will agree to send a new calculator to you. This calculator will be wrapped in "bubblewrap", without manuals, case or accessories. (In fact, some sellers in Ebay are just selling a batch of these HP35s replacements, as new calculators. I think HP should do something about it). It will arrive very soon, typically in two-three days. and you'll not be required to return the defective one, in most cases.

You can also try repairing it yourself. Some models are easier than others, and here internet is your help. However, all calculator aficionados are waiting for a book on HP calculator repair by Geoff Quickfall. He has put all his experience in that book, that he's now proofreading. I look forward to get a copy, and you'll all know when it happens.

If your calculator is old, then a repair is a definite possibility. Voyagers, HP41c, HP65/67/92/97, etc.: most of them can be repaired, and it will continue to be your trusty calculator. To do that, you can call us in Europe (we have a partner that takes pride in his repairs, and treats them as a challenge.

I have found the first organizer I ever had - and it was not a HP machine. It was a Psion series 5. I finally found what was missing - the power supply. Now I have finally switched it on, and it works!

It has not been used since I received my first Blackberry, around 2003. I remember I did my personal accounting with it. It was the first machine to have the Symbian operating system, developed by the then called Psion, which later changed names. Symbian was one of the many outstanding British developments, which end up in nothing due to lack of marketing clout. (This deserves another blog post: discuss the many outstanding developments that come from British creativity - and I am not from the Islands!). Eventually, Symbian ended up being the operating system of Nokia phones. Somehow Nokia managed to spoil it too, as did with the rest of it.

As it was a gift, I received it with a wonderful Mulberry cover, in black, which which it could be used without taking it out. It also had a place for a pad - that was still required then.

Tomorrow I will post pictures of it all.