Calculator blog

We have received several questions about the Overlay option in the HP15CE - so many that we have changed the name to "Cover". 

It is an HP16c overlay to be put on top of the keyboard. It allows the machine to behave as an HP16c if you have the means to transfer there the firmware of an HP16c. It is possible on the newest versions of the HP15c or the HP12c too (NOT Platinum). More details to come in following weeks!

There will be another option for HP15c cover too.

This HP16c overlay version has a little blurred yellow print - the jet seems to be too far from the surface. We'll receive it in a few days to try it mechanically - how it works. It can be used in any new Voyager calculator with the suitable firmware (HP12c -attention, NOT Platinum-, or HP15c CE)

Here is another picture fo the tests we are doing with overlays. difficult to get the process to get the colors right! Also the blue labels are still not well centered - next tests tomorrow! At least the keyboard works well and adheres well too: you need to shake hard the calculator to get it out. It will work well on that count!

We are in the final stages of preparing a cover for HP16c. The software will have to work on other "new" Voyager calculators. We have suitable firmware to do it. We are testing it, but I do not think we can run a fully-fledged testing process for it. We will have to work with it as is.

This is a printing sample of what we want to achieve:

It does not fall from the calculator, and can help you use your voyager calculator as a HP16c - the long-gone computer scientist calculator.

Will it work with the new HP15c Collector's Edition? If we can make it work with the latest HP12c, of course it can!

I cannot help but buy calculators that I like. The other day I spotted a 1987 HP12c calculator in quite good shape. It was still working, but the battery low indicator was blinking all the time. The way the calculator looked, it had not been used too often - so the batteries may have even been original! These calculators' batteries really lasted forever. Also the clicking of the buttons is like the original - clear clicking, but softer keys than the ones of the new HP12c.

But the nice thing of this calculator is that it came with the best leather case.

This time in Burgundy - I had it in the past in brown color, but never in Burgundy!

I still don't know if I'll put it up for sale, or with/without the case, or with my own leather case.

The new HP Voyager (HP12c, HP15c Collector's Edition)calculators have a connector in the battery bay that can be used to change its firmware. Theconnector is that 6-pin set just below the batteries. The previous version had the same connector, and it needed a special cable to do programming with it; however, the previous version had a TTL-level adaptor chip, and is not pin-compatible with the current connector - which runs a USB protocal (albeit with a completely different connector!).

I have tried hard to find the connector to buy or produce such cable, but after looking everywhere for it, I've been unable to get one, or even to order one for production. Now, apparently, there were close to 1000 units of the previous version produced by HP for the 2011 production run. These can be used, but they need to be changed to use the new pin mapping required for the USB connection. I will describe the cable changes in a future blog issue.

there could be another solution, but that involves more effort: you need to open the machine and solder a USB connector in a place designed for it. Only the nano-connector applies!

Why all this fuzz? because using it, you can alter the original firmware to get more memory ! there are instructions of what positions to change in the program memory to increase the memory, and also the palces to tamper to avoid problems with the MEM screen and program limits. You can find them in hpmuseum.org . Be careful with what you do because you can brick the calculator !

PS: if anyone want more precisions, please contact us at jose@thecalculatorstore.com

As 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!

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:

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:

• HP12c: 24 seconds
• HP15c CE: less than a second!

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!

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

• HP Prime goes from 189,99€ to 144,99€, 21% VAT included.
• HP17bII+ goes from 94,95€ to 89,95€
• HP12c Platinum goes from 74,95 to 69,95€
• HP12c "gold" or "classic" goes from 69,95 to 64,95€

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