This is the journal for the Calculator001 (dubbed "DL 13C") project. The original journal is in chronological order (oldest to newest), however this web presentation is made in reverse chronological order (newest to oldest).
I awoke this morning to discover that I had turned into a giant cockroach.
Today I discovered another ‘repurposing a 12C’ project at:
I’m a little dejected of course in discovering that others are working on a similar thing, and had started dong so before I did but I’m going to press on as (hardly at all) planned. FWIW, this project can be viewed as perhaps a smarter approach, in that it uses the discovery that recent 12C’s are completely revamped, using an ARM-derivative which ostensibly can have it’s firmware replaced (probably via JTAG?). I wasn’t aware of this (my failure in research), but anyway I started this project as a lark on a whim (inside an enigma?), so I excuse myself.
After I’m done with this project, I might explore this other project approach as well!
I cut the breakout board down, and shoved it in:
Time to cut the PCB:
Here is where it all fits together:
and imagine if this is where the CPU board goes:
Front and back case closed together; how it looks:
Laying the original display and keyboard bezel on top to make it look a little more ‘final:
OK, now I can either finish up my power problems (charging and regulation), or start on the processor circuit design, or setup the software development environment.
I found a suitable charging controller, and am working on the regulator. I can’t decide whether to use a simple linear regulator or a fancier switcher (perhaps SEPIC or flyback). My battery has such a tiny capacity, and while this off-the-shelf processor has various power saving modes, nothing will compare to the original. Oh yes, in that regard, I also have been thinking about using FRAM for the continuous memory aspect, since it is cheap, has a SPI interface, non-volatile, and has way more erase-write cycles than using a page of on-chip flash.
The minimum circuit design part is not too complicated – just figuring out which IO line I want to use for the display. However, one of the peculiar things about PIC controllers is that all the pins serve more than one function, so you have to be fairly judicious in your choices lest you prevent yourself form using some on-chip peripheral later.
Setting up the development environment will be new territory for me since I have not worked with this chip before. It is a MIPS derivative processor. Of course I will be working mostly in C, but still I’m not familiar with the tools. I’ll probably put the whole dev system in a VMWare image.
Anyway, enough for now. Wish I had more time to fiddle with it all, but I should be on the cusp of doing more fun things than cutting up plastic…
I decided to be a little lazy – I bought a ‘breakout board’ for the USB connector. I did this because the SMD connector will be too hard for me and my failing eyesight to reliably solder, so I splurged on a $5 mounted device onto a PCB, breaking out to through-holes which I can manage.
OK, I was too curious and so I cut the plastic for the USB connector.
I did it by first scoring the outline as best as I could with an Exacto knife, then hand-drilling holes along the outline using a .049” drill bit in a pin vise. Then I used an Exacto knife to finish the outline. I should not here that cutting this plastic is very easy. It’s like butter! (well, frozen butter). I was surprised at its softness.
Here the connector is stuffed into it’s hole.
Here’s what it looks like face-on. Sorry about my not-so-great Exacto-ing out of the hole.
and what it would look like with something plugged into the unit.
The astute viewer will notice a downward angle to the connected USB cable. This is because I had to drill from the inside, where I could score the outline of the hole from the connector. But, starting from the inside meant I could not come normal to the case side, but rather at a slight angle. The connector fits in at this angle. I will try to resolve this by removing a little plastic in the hole (which will have the unfortunate effect of also creating a little gap.
Also, you may note that the external plug has some exposed metal guide. This is because the connectors are spec’ed to permit getting through case, and my placing the female connector flush with the outside of the case leaves that allowance exposed. I will try to accommodate for this when I glue it in its final position. I don’t want to take this adjustment too far, though.
My USB Bitwhacker 32 has been in for a while, but I haven’t fiddled with it since I was concerned about other aspects of the project. This is a little dev board that seemed to have the desired hardware (namely the PIC32MX460, but also the crystal, some miscellaneous needed passives). I am using this because it is a huge boon to me not to have to fabricate a PCB and solder the quad flatpack. The pictures for the UBW32 are otherwise readily accessible on the web, but nonetheless:
The power connecter is way too big. I removed it and put the board into a trial location:
Alas, the mounted USB is still too big to fit into the case. I could gouge out the back completely to allow the connector to be accessible, but surely I can make it look better. Plus the stress of the insertion force needs to be tolerated. If I had control over the PCB, then I could mount it in the upper right (from rear; upper left from front). Since I will be cutting away that PCB (and it doesn’t have pads for the connector anyway), I am currently thinking about soldering wires directly to the connector, running them to the UBW32, and mounting the USB by epoxying it into place in the case. Here is the location I am thinking of, with a new connector resting in place.
I will need to cut some plastic! Yikes!
I don’t know which will be my first real cut: the PCB, for the LCD, or the case, for the USB connector. Hmm…. Well, I can still do useful work with the CPU card and the battery circuitry before I have to commit on the cutting….
The 10180 cells came in. It is about 2.0+ mm little longer than the original 357 stack (and about 1.5 mm less diameter). This is enough to make it not fit as-is. The positive end is formed from plating the PCB, so I can’t modify that end. Instead I tried transferring a couple coils of the spring for the negative end to the outside of the battery compartment (where it meets with the PCB. This, with the help of my small screwdriver, was enough to get the battery in without modding the compartment. It will not be easy to remove and replace without the screwdriver help for leverage) but that’s OK I think. I intend to leave the rechargeable cell in permanently and charge it off USB power.
Now I must devise some charging and power conversion circuitry.
And my next dreaded task is figuring out where/how to place the USB connector….
I spent some time yesterday obsessing over battery matters. This device is so famous partly because of its efficient physical design. Really, it is still fantastic even today when it comes down to it. This isn’t a great thing for me as a re-designer, because I am trying to stuff off-the-shelf stuff into an otherwise very efficient case. Well, all my new fab things do require power, so is a challenge to re-purpose this. As to my post on Aug 29 (d) disregarding power: “ahhnnn; wrong answer!”.
I think trying to power of SR44s will be a problem because my off-the-shelf chips and display will not have the power-sipping demeanour of the originals, so I have been considering rechargeable lithium cells. My original thoughts were thin prismatic cells but event the thinnest are a bit thick. I have about 3mm max. I can squeeze another mm if I cut out of the back case and rely on the backplate to cover up the cutout. It’s still a bit much.
I discovered the most amazing thing, though. A 10180 cylindrical LiPo. This is very similar in size to 3 SR44’s, so conceivably I could stick it in the existing battery compartment! This is really great, I think. Turns out these cells are pretty rare, and folks have been looking for them for a couple years (based on searching through forums; they’re apparently used in some exotic miniature flashlights). Also, fatefully, they have recently appeared and so I bought five of them immediately for fear of them going out of stock for a while. What luck! I didn’t buy more because lithium cells unfortunately do not shelve well – they will become unusable after time even if they aren’t used at all.
My new challenge will be: a) was my impulse buy worthwhile? It’s only half the capacity of the SR44s, and at a lower final voltage; b) lithium is a bitch to deal with. I am old and lithium rechargeable was not a mainstream chemistry in my day, and I don’t have experience designing with it. If you don’t do it right (charging) it will explode, ruining the product, and quite possibly seriously harming the user and causing all sorts of collateral damage. Frankly, it’s quite amazing to me that we even design with this stuff at all. But the power density is quite alluring.
Anyway, my new challenge will be to charge the cell, to transform the cell’s energy into a form that can operate the equipment, and to do that all safely. Oh, and also stuffing any needed electronics in the space available.
Frittered away some time thinking about replacing the ‘badge’ on the calculator with something fanciful.
I decided to use the designation ‘13C’ since HP never made a calculator with the number ‘13’ (I guess they are superstitious). I thought this terribly clever, but it appears all the rest of the world already has thought of this already. [Side note: whenever you think a thought you have is clever, it very nearly always means someone else has already thought of it – the likelihood of truly original thought is low, but you shouldn’t let that dissuade you from acting on your thoughts. Validation is a good thing.]
Anyway, I indulged myself by making some mockups. In respect to the brand (and indulgence of the ego) I took off ‘HP’ and replaced it with ‘DL’. I did this a couple ways and am not fully satisfied with any, but whatever – enough time wasted. Here they are:
A logo preserving the 'hp' lettering. The 'L' looks silly:
Here the 'L' looks better, but the balance between dark and light doesn't look so great, I think:
Here is a better light-dark balancing, but still doesn't excite me:
Here is an alternative of the first version, but with a different 'L' treatment:
OK, I couldn’t resist messing with it more at least just a little.
So, since I had chosen a display, it was nearing time to cut the PCB to accommodate it. So I needed to map out what were the traces that I needed to keep for the keyboard from the ones I didn’t need that went to the original LCD display.
Work work work work work… Anyway, I haven’t had much time to do more. However, I did spend a little time trying to find LCD’s to put in. My perfect world would be an alphanumeric, or graphic display. Alphanumeric is more likely to happen because of the existing aspect ratio of the window – text is implicitly a linear form, whereas graphics tends to be an area.
The window should neatly accommodate the display of the very common 16x1 displays with the super common HD44780-derivative controllers. (Jeez; I remember programming drivers for these in the late 1980’s!).
I have had a lot more trouble finding a suitable unit that I would have expected. The problem is that all the surrounding encasement is to large for the calculator – even if I were to grind out plastic and such. The problem gets even worse if a backlight enters the equation. The original units don’t have backlights, so I am not got to push for it, but it might be nice if the unit is powered from USB or the like.
I finally found something that will fit. It is a 16x2 unit made by Hantronix, called the HDM16216L-S “16 Character x 2 Lines, Very Small Size, LED Backlight” display. It fits in the case! Even with a backlight! However, it is incredibly ugly because it is too small horizontally. If there were a 24-character version, it would be perfect.
In the interest of moving the project forward, I am going to punt on this issue and use the less than optimal display. I got some on the surplus market for $5 each. So I bought 5 of them, which should be more than enough spares if I ruin one.
It’s really a shame on not having a 24 char version. That would turn this from a compromise into a real win… The only thing that would be better would be if the display were graphic (giving total control over the presentation) or if it were old school black-on-white (these are the black-on-yellowgreen kind).
Oh, well. Moving on.
I never really worked out power. Obviously the original “3 button cell” approach will probably not work since I am using common off-the-shelf stuff, but – like with the display – I am going to avoid obsessing over it. I would like to have a lithium ion battery that I can shove somewhere, and forgo the whole ‘constant memory’ thing in favor of persisting to flash, with a ‘soft off’ key that causes the persisting (along with when powering off because of inactivity). Professional designers – as well as amateur designers having more wherewithal – will scoff at this, but as I am neither, I rebuff such scoffs…
Here is the display:
For reference, here is the display next to a ‘common’ 16x2 display (the item pictured is a DUKPT PIN Pad I had constructed some years back).
Here is the unit positioned in the calculator, centered where I will finally place it. You can see this will be a bit ugly because of the wasted horizontal space.
Here I am left-justifying the display to give an idea of how it might look if but only I had a 24 character version of the same.
Oh, here is one other display option I considered. It is an LED alphanumeric display, the popular (and expensive) HDSP-2112. There was no way it could have fit, but it would have been so very cool I think:
The three major problems with using this otherwise exquisite display were
a)
Size
There would have had to be surgery to the plastic case (plastic surgery?) beyond
the case’s dimensions. (I am
going to have enough of those challenges already with the CPU unit!).
b)
Length
The unit comes in 8-char, but I would want 10 at a minimum to be meaningful.
Especially if I don’t have any way of presenting commas, dots, or
substitutes for the annunciators.
c)
Power
It’s LED. slurp.
I began disassembling the 12C today. Everyone knows what a 12C looks like, so I didn't take a 'before' shot, but in retrospect, this was a mistake for the posterity of this particular unit, so 'note to self' on that. I took other photos during the process of disassembly.
First, I removed the feet, which cover the screws, and unscrewed it. The back came off easily, which cannot be said for other units I have disassembled before. This is because HP used to put a wad of double-sided foam tape between the PCB and the back panel, requiring careful separation. There are two grounding springs that need to be watched-out-for to avoid losing them. These springs provide electrical continuity amongst the three metal plates on the front and back.
This is a late model, and is of the single PCB design, rather than the two PCB design of prior times. The prior design had a separate display and keyboard circuit. I don't know if this is good or bad news for me, but I know it means there is a Dremel in our future(!).
As anyone knows, the Voyagers have their PCB secured by way of 'rivets' formed by melting the ends of plastic studs that extend from the front half of the case, thereby creating the rivet 'heads'. These heads must somehow be cut off in order to remove the PCB. Rather than shear them off, I meticulously (tediously!) carved around the head to take the fastener back to approximately the original unmelted state. The idea being that maybe I would re-melt the restored studs to refasten the board. I don't know if this is what I'll wind up doing, though; we'll see. You have to take care when removing the PCB to not over stress the board, and shattering the LCD.
The separated case and boards are shown:
The small screwdriver and Exacto knife would be my friends for a few hours…
You can see the unit still works:
And the keyboard is functional:
I also ran a self-test (not shown) and the display works as expected. This will be the last naturally intended thing this calculator will display before receiving a new brain....
Removing the LCD was straightforward, but a little troublesome because the steel frame is a bit springy, confounding attempts to straighten the bent-over tabs, which secure it to the PCB. I found it easiest to straighten the tabs as much as possible, and them pull the top edge over the PCB (hinging on the bottom edge), then pushing the bottom tabs through. After the LCD has popped out, it is much easier to finish straightening the tabs.
The keys are separated from the 'snap disk' keyboards by a rubber sheet. This old, worn unit had a few well-used keys that had punctured through the sheet (no big deal), namely the four arithmetic functions, and the Enter, and backspace (and oddly RCL). I removed this sheet (and washed it; it certainly would have provided good DNA material from it's previous owner!), and then faced the array of lose keys. I decided to use a piece of duct tape, and press it against the backs of the keys and remove them en masse. This way the keys could be kept tidily in their original location.
Now that all the internal parts were removed, the daunting task of removing the metal plates remained. I decided to remove the LCD bezel first, because it seemed to have the least surface area with glue. I decided to use a hair-dryer to heat the plate, thus softening the adhesive (somewhat amusingly, the hairdryer is from the 1980’s also, contemporary with the calculator). After about five minutes of heating, I tried applying pressure the back of the LCD bezel. It did show signs of easy separation, so I continued with this approach.
I continued heating and pressing until left side gave way completely. I used my small standard screwdriver to wedge between the separated portion and the plastic case, continuing to heat with the driver. It is important to not separate the plate too far from the case lest one permanently bend it. This is particularly important because, if you dent the front you can hammer it out, but if you bend the top edge (which is at 90º) you will likely have a permanent problem. I continued heating and advancing the wedge of my screwdriver until the plate was completely removed. I took off the logo simply by plucking it off (It is held on by a piece of double-sided foam tape).
I was worried about how to take off the keyboard and back plates. They had such a large surface area. I didn’t think the hairdryer was going to work so well because of the cycling between heating and separating would give the glue time to harden and result in damage to the soft aluminum. I got the idea of submerging the panels in hot water, and doing the work while underwater, to facilitate continuous application of predictable and even heat. ABS plastic (which I’m guessing is what the case is made from – I know it was popular at the time these calculators were produced) has a melting point of 221º F, above boiling for water. I filled a pot mostly full and brought it to boil, and then added tap water to take it down to 195º F to add a margin of safety against over-softening the plastic.
I decided to do the back first in case I caused damage and wanted to try a different approach. This method actually seemed to work well, though, and I used the thin blade of the Exacto to start the separation at an edge, and following with the small screwdriver serving as a wedge to advance the separation.
Incrementally advancing the screwdriver left to right, along the long dimension of the plate, and then downward to the other edge, the plate was eventually separated without any damage, distortion, or denting. The plastic case did not fare quite as well: I had become over-aggressive on the first separation activity (the one in the picture) and the area where I had first inserted the screwdriver/wedge showed some warpage. I put the case back in the hot water for a few minutes and pressed down with implemented while under water for a short while. Then I removed it to a towel and quickly resumed the same pressure while the plastic cooled. This restored it almost completely, leaving only the slightest remaining warpage that will very likely not be noticeable once the unit is reassembled (you have to use light glare to see it now. It actually has a benefit in this instance: the battery cover was hopelessly loose, and the previous owner clearly used scotch tape to hold it in place (because there were tape remnants embedded in the thumb grooves, along with decomposed adhesive.
Encouraged, I finally decided to try the same approach on the keyboard panel, which I was dreading because of the susceptibility to bending that the gridwork of holes produced.
The process started off well enough, however:
Using the thin Exacto to work the front edge side-to-side, and the screwdriver to simultaneously advance the newly created edge front-to-back along the rails of the keyboard grid, the plate was eventually removed. The progress of separation can be viewed as an advancing front, initially perpendicular to the line extended from the top left, to the bottom right, and starting at the bottom right. As this front advanced, it rotated around the top right, so as to finally be horizontal with the top edge. That is, like a clock hand sweeping from 37.5 minutes, to 45 minutes. At the end, the plate was hinging away from the case and was easily pulled away.
NOTE TO RESTORERS:
While it worked well, I’m not so sure I can recommend the water bath approach for all purposes without some caveats. The treatment may have had a bad effect on the paint of the plates, which became very easy to peel off. You can see that when I tried to remove some of the tape remnants from the battery compartment that the paint underneath easily was pulled off. This may be a natural effect, though, and less one of the water bath. The plates are aluminum, which oxidizes readily, and the age may have build up an oxidation layer between the metal and the paint that facilitates easy separation. When the unit was received there was paint removal already, in a circular spot (like from a hole-puncher, and at the upper right edge, and lower edge.
Maybe the hot water bath accelerated what was already happening naturally. This didn’t matter to me because I intended to repaint and rescreen all of this for my custom calculator, but it might matter to restorers/repairers.
Also, the water bath caused lightening of the plastic case. I think this is due to a leach-out of the plastic colorant (styrene is naturally white). I tried some plastic restorant to no avail on an area, and may later try re-melting to confirm the hypothesis, but if my leach-out hypothesis is correct, then the restoration process will either be adding the color back, or removing the bleached material. I will worry about this later. It’s not that critical an issue for me, but I imagine it would be much so for a restorer.
The backs of the removed metal plates are covered with either a gummy film (the display bezel), or a sheet of double-sided tape (the keyboard and back panel).
I decided to simply peel the sheet off the back panel and keyboard. When I did this, I started at a workable corner, and pulled the tape 180º back upon itself. I did this to remove any force perpendicular to the plate, which would cause it to bend and be distorted. Whenever the force needed became large enough to where I feared the metal would give way, I rotated the force vector about its origin to cause the tape to give more easily. In this way, for instance, I peeled the sheet off the back by starting at the lower right corner, pulling straight back upon itself in the 10 o’clock direction until it became a bit snug, and then pulled in the 8 o’clock direction. Eventually the sheet came off and no damage was incurred upon the back panel.
Even more gentle and careful attention was given to the fragile keyboard panel, but the same basic technique was used. It was in some ways easier because the gridwork also weakened the adhesive sheet’s hold upon the plate.
The front bezel consists of the visible plate, with a glued bracket holding a plastic lens in place. I removed the bracket with my Exacto knife by separating the sides, and then the long bottom edge. Then I gently hinged the assembly along the top edge, which was otherwise inaccessible due to the folded-over edge of the plate. I used the Exacto to sever the glue at that hinged edge, and pulled off the plastic lens.
I rubbed off a bit of the glue from all the parts involved, but I think I need to get a proper solvent. I tried what I usually use in a pinch: some Sheila Shine. Sheila Shine works because (I think) of it’s toluolene, but it contains mineral oil, too. I decided that since I also need to get some methylene chloride to strip the paint, I might as well wait and get proper glue solvent (if the paint stripper doesn’t work well enough itself).
I scanned the plates before I stripped them in case for some reason I needed to know what it looked like beforehand (like if I want to match fonts, or placement).
[this is not the original hi-res scan]
I put away all this stuff for later, and set down to write this entry. Writing this entry took far longer than doing the work.
Impatient to do more, I broke out my hot air rework station and desoldered the components from the PCB. There are only three passives, what appears to be an inductor, a resistor, and a capacitor, and then one chip. I stuck these in an antistatic bag for posterity and scanned the back and front of the PCB.
I discovered that I could use hot air from the rework station to quickly melt the surface of the plastic case, and cause the white discoloration – picked up in the water bath plate removal process – to vanish. You have to be quick, of course, or there will be hopeless warpage. I treated the whole unit, though I messed up the bottom piece a bit. I undid the benefit to the battery cover (and tried to make it good again, and made it a little worse). I also made some of the seam on the forward edge of the bottom shell to sag, making a little ‘sad lip’ between the Enter and 0 key. We’ll see how bad it winds up being when reassembled. Restorers will again want to be careful with such a technique. I used 500º C on the hot air with no nozzle. The theory is the high heat would melt just the surface, leaving the bulk of the plastic underneath cool and solid., but I wonder if that was not the best approach since the effect seemed to take some time, and by then so much heat energy had been transferred that the whole body became plastic. Maybe I needed much higher heat for a much shorter duration (I can’t do that) or a lower heat to give more control and just be conscientious about support to prevent warpage. Who knows, I’m done with it for this unit.
Since I am Frankensteining mine, I don’t think it will matter. There’s probably far worse ahead….
[this is not the original hi-res scan]
[this is not the original hi-res scan]
The second calculator specimen arrived today. It is in more worn shape, made in Singapore 1994. This is the one I’ve chosen to disassemble first since it is in the worse shape.
No work done.
The first calculator specimen arrived today. It is in great shape, made in 1998.
Also arrived is a development board for the PIC32MX460, called the ‘USB BitWhacker 32’, which I got from SparkFun Electronics.
No work done.
It is common for an engineer, at the beginning of a project, to come up with a lot of kooky ideas. Usually these are kept in check by other stakeholders, but since none of those folks are around here, I happily can do anything I want without respect for marketability, timelines, budgets (OK, well yes only to a degree), or pesky technical feasibility issues like battery lifetime.
Some ‘mad’ ideas that have arisen so far:
I don’t have the wherewithal or time to try to knock off a design like the HP-11C. The beauty of the device is in the physical construction, and I have never been so good at the physical. I got a kooky idea: why not re-purpose an existing calculator? Gut the processor, and reuse the case, keyboard, maybe display.
This would be a heresy to Voyager officianodos, and also a costly prospect for me to acquire a device to hack, however there is one odd thing about this collectable: while almost all the Voyagers were discontinued in 1989, one of them is still in production even today: the 12C. It is the version focused on doing finance-related calculations, and became such a hit that it never went out-of-production. As a result, this model is so commonplace that I can get a used unit for a few tens of dollars. I don’t think anyone would curse me for Frankensteining a 12C – even a vintage one. So now I scour eBay for used 12C’s, and intend to get 3-4 units.
[I am breaking this initial post into parts, because these ideas came in different periods in the past, and wanted to somehow convey that, rather than making it seem that it all came together this way at once.]
So, ‘just the other day’ (which really means anywhere from years to months ago) I got the idea of physically making the ‘cryptographic calculator’. Also as of late I got the idea of making it resemble the design of the HP-1xC, which I loved so much. I have a tendency of enjoying putting a little bit of artistry in one-off designs like this. I am no artist, to be sure, but as one rarely gets to be strictly autocratic in one’s professional work, these little projects provide an outlet for doing something fun (and sometimes even outrageous).
For some time I have off-and-on thought about a ‘cryptographic calculator’ – which is imagined as a specialized calculator that has functions for doing fundamental operations for encryption, such as bignum arithmetic, but also built-in primitives for doing DES, AES, RSA, DH, etc. There have been many times where I could use such a device, and have written several utility programs for performing various general and specialized operations.
Also for some time I have had a minor obsession with HP Voyager calculators (i.e. the HP-11C and family). The HP-11C was my first engineering calculator. O! To be sure, I did own a TI-30, and other contemporaries, but the 11C was different in some way. If you had one, you’ll understand. These calculators appealed to their owners in a way that somehow elicited a sense of ‘connection’, and the calculator became a sort of extension of the self as a kind of ‘numeric companion’. It was quite like owning a pet.
Anyway, I had given my 11C in favor of a 41CX, a 28S, and finally a 32SII. I got out of electrical engineering and didn’t really need a scientific calculator anymore, but still longed for my 11C. (Actually, I always longed for a 15C but I couldn’t afford it at the time, and anyway it wasn’t available at the Sam Solomon’s where I shopped.) The 11C (and friends) had a horizontal layout, which was unconventional for calculators. Calculators were (and still are) largely vertical, presumably to better facilitate holding in the non-preferred hand, but I liked the horizontal layout because I could better see the ‘function’ are of the keyboard to the left of the ‘digit’ area, and plan my hand-eye coordination better. And usually I use the calculator on the desk.
I admit having felt a little embarrassed about being reminiscent about a calculator made in the 1980’s, but I was vindicated when I stumbled across several museums devoted to the calculator, petitions for their reproduction, and quite a healthy collector’s market in online auctions where the devices sell at a multiple of their new cost in the 1980’s! So I was definitely not alone in this thinking.
