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Musings and comments about our common interest


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A new glue for HP repairs


IMG_0583As you know, i have been using E6000 glue for some time. However, the producer has reformulated the glue due to regulatory reasons and there is no more E6000 - there is only E6000+. This is not, by any means, the same product and I cannot recommend it. It does not withstand the same forces or stresses as the original. I have had to re-do several repairs and I was looking forward with anxiety any repair that required gluing.

For some time I have been using epoxy 2-component glue. This requires mixing it properly before applying. You consume a lot, and then when you apply it, the layer is thick - in some cases, far too thick, and it cannot work properly (for example, in lower post repairs). I had to redo several repairs due to the excessive thickness. 

A customer that is also into modeling referred me to a small German company: SCHWANHEIMER INDUSTRIEKLEBER, and their product Industrial Adhesive no.100. They also recommend a primer for difficult plastics - of which our calculators are made of.

This material hardens immediately under pressure: you apply a layer on just one part (it is extremely fluid so be careful) and then press both parts together. If the parts are from our damned calculator bodies, please use also the primer and let it act for at least 10 seconds before applying the glue.

As the material is very fluid, the layer is very thin, and with a good pressure between the parts, you get a very strong bond, and it looks far cleaner than with previous glues. I am considering trying to fix the domes directly - without using the parts we have developed. Let's see how it works over time and we'll be back here with the results.

These glues are not cheap, but they are consumed sparingly (the layers are thin), and the result has been impeccable for the time being!

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New, ecological packaging for the HP Prime calculator

We have ordered a box of HP Prime calculators with "BOX" product description. These are special, cardboard boxed HP Primes - much more ecological than the ubiquitous blister. 

This is how the box looks like:





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Another speed comparison for the HP15c Collector's Edition


Let's try another speed comparison for the HP15c Collector's Edition, this time with a financial workhorse for financial duties: the HP12c (original version)

We will compare the time to calculate the interest rate in a long Time Value of Money calculation. The HP12c using its native TVM functions; the HP15c, using the Time Value of Money program in the Advanced Functions Manual (shifted to another place in the program memory - with so much memory I have entered several other programs too in lower memory positions)

The data for the problem:

  • 360 periods (n)
  • 480.000€ initial value (PV)
  • -2050€ payments (PMT)
  • 0 final/future value (FV)
  • Solve for i

There is no general analytical solution for i : there is no alternative for iterative solving ! The HP12c uses an optimized machine-code algorithm, but it has a slow processor, dating from 1981 and running at 880 khz (give or take) - 38% faster than the HP41c. On the other hand, the HP15c is running a keystroke program, using labels and the HP15c's Solve function called from within the program, running the keystroked TVM formula in a loop.

The results:

The newest HP12c is faster than either - but has none of the other features of the HP15c.

So, having entered programs for %T, NPV/IRR (using solve too) and TPV, and despite how comfortable feel the incr%, T% and % of the HP12c, I will take just one calculator with me! Still a lot of memory to solve equation systems oe enter other programs. There is more concern about the label codes left than memory!



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Price Reduction for new HP calculators


We have recently reduced the price of most HP calculators, due to higher volume:

Now prices are more competitive - in particular the HP Prime that is clearly the best calculator there is now!



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Important announcement regarding HP15c CE deliveries

We have learned some things about the coming production and deliveries of HP15c Collector's Edition:

  • Production is scheduled to take place around the 10th of July.
  • Air freight deliveries will typically occur during week 3rd or 4th of July.
  • So far only The Calculator Store has ordered Air freight (at a cost!) : 600 units, of which 490 are already sold. We will begin to ship by the end of July.
  • The rest will be shipped by boat, and will arrive not before the end of August/beginning of September. 
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Calculate digits of e


IMG_0561Several years ago Valentín Albillo posted a document, "Long Live to the HP15c", where he lauded the HP15c, describing how wonderfully put together it was. Also, to demo the calculator possibilities, he created a program that calculated digits of e, using the expansion e = 1 + 1/1! + 1/2! + 1/3! + 1/4! + ..., and using matrices.

The method he used was able to get up to 208 digits of e in the available memory of the HP15c. He himself said the program was not optimized for performance - indeed, he introduced a Pause displaying the digit being calculated, so you can imagine how slow it could be.

The program gets 8 decimals of e per register used; the input to the program is the number of registers to be used. The time to get 208 decimals is 62'43'' with the original HP15c. The program as such could not be run on the HP15c LE, since it had the Pause bug, and this program uses PSE once per iteration!

I have run the program and found that for the HP15c CE the biggest time consumer was the pause step. (it did work well - the PSE bug has been erradicated in this firmware!). I removed it and the previous RCL I, and got 21 seconds for the 208 decimals - quite an improvement from the original.

The maximum digits in the original HP15c were 208. The program uses 2 matrices with the same size, in this case 26x1. Therefore it is 52 registers used. The program occupies 10 registers, and we have left 3: we have occupied 65 registers.

Valentín told me that to go further we need to get just 7 digits per register. So far we have lived with 8 since there were 2 max digits for carry - so 8+2 = 10 which is the mantissa size in the HP15c. However, for more than 26 registers the carry digits are 3 - and we need now to plan for 7 digits + 3 carry = 10 mantissa digits per register. So step 11 needs to be changed from 8 to 7. Now we could only fit 26*7 = 182 decimals in the original machine - but now we have additional memory.

With this new program we can get up to 42*2 + 10 + 3 = 97 registers used, with 42*7 = 294 digits of e !! 

The speed is still very good: less than 48 seconds to calculate all of 294 digits ! 

Another example of the power of the new HP15c Collector's edition !!

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Selling the HP15c CE to non-fanatics

Captura_de_pantalla_2023-04-26_a_las_9.15.21We created this website because we are calculator fanatics - much like you. And we see the beauty of the HP15c. In some cases we've been longing for the calculator for a long time. In any case, no one needs to give us a reason to get one.

However, it is difficult to "sell" the HP15c to non-fanatics. As example, to my children. Both are technically-minded: one has just finished sophomore year in engineering, and the other is in international baccalaureat and intending to get into engineering too. Both are users of the HP Prime, and swear by it. It gives them an edge compared with their peers that use Casios or Texas. 

However, it is difficult for me to convince them to get a HP15c - when it becomes available within a year. 

The first obstacle comes with RPN. No matter how I insist, they prefer the text entry method of the prime - with a clear view of the equation being introduced. They have never enabled the RPN mode in their Primes.

The second obstacle is the small screen. You need to know what you are doing at every time, You need to know what you have in the four stack levels. Also you have no alphanumerics, and you can't get any graphics. What is the point, also, to edit a matrix in such a cumbersome interface? Can't touch the HP Prime when editing matrices, programs, etc.

Calculating with the HP15c has become second nature for most of us - and that gives us incredible speed when using these machines - well above in many cases than when using the HP Prime or the HP50g - simply because we know the machine better and RPN helps us. But this speed does not apply to our children. 

So, I have not been able to convince them yet. At this point, they cannot see any instance where they could not have a Prime with them. I can tell them that in my professional life I have seen people with their 48 on their tables - but for any of them I have seen 4 or 5 with HP17bII or HP12c (gold or platinum) and 40 people using 4-bangers. There is just some times when you cannot take a Prime with you - but there will always have a place in your jacket for a Voyager.

Me? I like the landscape format of the Voyagers, and I am now having a good time using the HP15c for really everything now. They will come onboard sooner or later.

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Solving a 8x8 equation system in the new HP15C Collector's Edition


We have tested the matrix capabilities of the new HP15C Collector's Edition, by trying a 8x8 equation system. This was completely impossible to do with any of the previous releases: they maxed memory allocable to matrices at 64 - so you could only invert a 8x8 matrix - but not solving a system since you needed the independent values' vector.

We started creating the two matrices, and filling them with random data, in the hope they would not be singular. To do that, we wrote a short program using the USER feature so that it fills cell by cell of both matrices.

Here is the result:


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Just in...

Here is what we have received this morning - aHP15c CE test unit.

Let's do a proper unboxing tonigh, shall we?





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