Texas Instruments TI-2500 Datamath (version 1)
1972 I spotted this hiding in a job-lot of electronics in 2021 and noticed straightaway that it had the CE/D key that tells you this is the rarer 'version 1' Datamath. I bought it not knowing whether it would work or not. This version of the TI-2500 takes six AA size NiCAD rechargeables; I've dismantled and cleaned them because they were quite corroded at the ends and I've included them in the photo – the sixth one rolled unnoticed out of shot – so you can see what they look like. I'm powering the calculator briefly from an external power supply at the moment but I suppose it wouldn't be too difficult to build a new battery pack. I hooked this up briefly to a DC power supply for the photo. You should never use early TI calculators without their batteries installed if you use their original TI power adapter which will just provide a low-voltage but still AC supply – a diode in the calculator rectifies the supply to DC and the batteries act as smoothing capacitors. The connector on the top edge of the calculator is a non-standard three-pin one – the version 2 uses a barrel connector. At first glance it looks almost exactly like my version 2 Datamath, but when you put them next to each other there are several differences besides the obvious clear entry key on the top left of the keyboard. The version 1 is smaller (has a lower height). There's a little notch in the beige plastic surround below the decimal point key too. The line below the TI logo is a ridge on version 1 and a groove on version 2. The lettering around the chain/constant switch is more widely spaced on version 2. Maybe the entire moulding is different. It's very different inside, as it needs to be to accommodate six batteries instead of four, and there's a battery compartment door held on with two screws; the version 2 model has no easy user access to the batteries. Internally, version 1 has multiple circuit boards whereas version 2 fits all the components onto one board. This version was only made for five months before being replaced with version 2. It cost $119.95 in the US when introduced in 1972. That's about $760 in 2021 when adjusted for inflation. The price plummeted to under $10 in the following few years, partly because subsequent versions were cheaper to make. Note how the display is made up of two sections with a split down the middle. There's a 9th digit on the far left for an error symbol (version 2 doesn't have this). To save battery the display has a 'battery saver circuit' (according to the sticker on the back) that switches off after 15 seconds (an annoyingly short time) and the CE/D key (D for Display) brings it back on without affecting your calculation. The main chip in mine is a Texas Instruments TMS0119NC dated 7238 (38th week of 1972) and there are two Texas Instruments SN75491N chips dated 7239 – I presume these each drive one half of the display. The serial number is A004795 and it's marked 'Made in Europe by Texas Instruments'. The shape of the mouldings in the battery compartment suggests this is from the first production batch. There were one or two earlier (though still 1972) and slightly different versions of the TI-2500 with white bodies including the so-called version zero. See the Datamath website for more information about this iconic calculator and its development. Box: N Case: N Documentation: N
1973 When Texas Instruments entered the calculator market in 1972 they introduced three models at the same time: the TI-2500, TI-3000 and this TI-3500. The TI-2500 was the handheld 'Datamath' model and the other two were desktops. The desktops were going to be called 'Deskmath' but that name only appeared on prototypes or pre-production models. The TI-3000 does not have the black keyboard surround or the switch for the number of decimal places, and uses an eight-digit display instead of the ten-digit display on this one. The TI-3500 cost $99.95 on its introduction, which was $20 more than the TI-3000 but $20 less than the smaller TI-2500. It's a medium-size desk calculator with a large and super clear Burroughs Panaplex II gas discharge display, surely one of the best calculator displays ever made. It's really a 10+1 digit display – the digit on the far left can show a minus sign or one of two different error/overflow symbols. The TI-3500 uses 'formula entry' so there's no separate equals key. But apart from this, it works like any calculator today does and is very usable with no real quirks or logic bugs. The keyboard is really quite noisy and old-fashioned, with a light touch and a 'clickety-clack' sound that's definitely from the past. These are not common in the UK and after looking for a while I ended up getting this from the US. It cost just over eleven pounds, but postage and customs charges more than tripled this. It's in really good condition though, and came boxed with the original dust cover and even the famous letter from the VP of Texas Instruments inviting customers with a problem to call him personally. As you'd expect this mains-only calculator from the US needs 120V so I have it plugged into a step-down transformer to convert from the UK's 230V or so. Box: Y Documentation: Y Case: N (dust cover instead)
Texas Instruments TI-2500 Datamath (version 2)
1973 I picked this up in 2020 because it was in great condition and had a very intact original box (the black and white version) with original US power adapter. I paid just eight pounds on Ebay. The Datamath was Texas Instruments' first calculator, made entirely from American-made components and assembled in Dallas. This is a version II Datamath (the only visual difference (from above) is that a 'CE' key replaces the 'CE/D' key on version 1) so it has four cells in its rechargeable battery pack and you have to remove screws to get inside. The battery pack is not designed to be user replaceable, though it is possible. Because the US adapter is 120V, I didn't attempt to power this up from the mains. Instead, I removed the crusty old rechargeable battery pack, soldered in the wiring on a new battery holder and inserted four 1.2V AAA rechargeables. It fits right in the space where the original AA-size battery pack goes, secured by the old strap. To my surprise it powered up immediately and all the keys work perfectly. I disconnected the wire from the mains power socket which led straight onto the battery pack as far as I could see and didn't look very safe. It's super simple, with no memory or percent or anything, just a switch for chain or constant calculations. The power switch is on the left side of the case. It's 43mm thick and weighs a heavy 274g. The display is red LED and eight digits. it feels very solid and well built. This is a late 1973 model. The keyboard is the very reliable Klixon™ keyboard developed by TI in 1960; it uses hermetic miniature and sub-miniature snap action gold-plated switches, which have been used over the years in a wide range of applications including the Space Shuttle. Inside is a TMS0119 processor. The Smithsonian Institution says TI engineers Gary Boone and Michael Cochran succeeded in creating the first microcontroller (also called a microcomputer) in 1971. The TMS1802NC was a single-chip microcontroller which was announced September 17, 1971 and implemented a four-function calculator. Presume the 0119 is a development of it. The date code on the chip is '7347', meaning it was made in the 47th week of 1973. The power adapter has a November 1973 date on it, while the old, furry, battery pack is dated Oct 73. I have a Which? magazine report on calculators for 1973 that lists the UK price as £35 or about £430 in 2020 money. At launch the US price was $120 but this soon dropped. Box: Y Case: N Documentation: N
1973 This was TI's first attempt at a pseudo scientific calculator, though of course it doesn't have any 'transcendental' functions like logs or sines and cosines. The enhanced (compared to a four-function calculator) function set includes reciprocal, square and square root, which is nothing special even in 1973, but what is unusual is the SR-10's use of scientific notation. And it has a 12-digit display so can do it properly. The lack of any kind of memory is a bit of an issue though. The display is twelve individual digits rather than the groups of four seen on the TI-2500. With no bubble magnifiers, the digits are very tiny indeed. There are five ICs on the busy pcb, four of which are of the Texas SN75493N type (dated 7321 and 7325) that I assume drive the display. The main IC is a TMS0120NC dated 7315. The display blanks after a few seconds to save battery. The keyboard is a proper Texas Instruments 'Klixon' unit and works very well. Logic is pretty good with no major failings. Power comes from three AA size NiCAD rechargeables or a mains adapter. The TI mains adapter provides a stepped-down AC supply only so you have to power this with the batteries in place if you use it. A diode in the battery compartment rectifies the supply. The batteries are user replaceable and just slot in like regular AAs. The rear cover has to be removed with a screwdriver to get to the batteries. Bought for eight pounds in 2021. This example was made in Italy and the serial number is 511478. This is the second version – the first has the model number moulded in below the display in the black surround. When introduced in 1972 it cost $149.95. Dimensions are 158 × 78 × 38 mm. Box: N Case: Y (zipped pouch with very soft padded interior) Documentation: Y
1975 Introduced in 1974, this added a four-key memory and decimal place selector to the TI-2500 Datamath, but in a heavier (317g with batteries) and larger case. The styling is half way to the more recognisable wedge shape that Texas is famous for. The battery compartment is user accessible; it would have been supplied with a set of rechargeable batteries originally. Mine doesn't have those but it seems happy with regular AAs. Perhaps alkaline batteries weren't common in 1975. Mine is the second version of the 2550 (not to be confused with the TI-2550 II) which has an LED display with bubble magnifiers. Earlier ones used a flat Bowmar display. The 'r' shape on the left of the display is the memory indicator. After the cute and much lighter weight TI-2500, this seems like a bit of a brute, especially if you compare it with something like the slick-looking Rockwell calculators from the same period. It's a 2020 Ebay purchase and not a bad one, though some of the keys need a firm press and the % key sticks occasionally. I suspect it's been used more than my TI-2500 which has a superb keyboard. It was very grubby on arrival but cleaned up quite well, except for the key edges, which seem to have scraped on the paint of the face plate and are stained rather permanently. The instruction book is dated January 1975. It was made in Italy. Box: Y Case: N Documentation: Y
Our family's first calculator bought in the late 1970s. Still works perfectly forty-odd years later. Many years ago I had to add some padding to the inside of this to get the top row of keys to work. The Datamath website has info on this calculator. They say it was introduced in 1976 and uses the TMS1043 single-chip calculator circuit. It cost £26.95 when new, which is about £123 in 2020 money. Box: N Case: N Documentation: N
1977 This is reputedly the best selling calculator ever, selling more than 15 million units from its introduction in 1976 to its demise in 1983. The TI-30 is a legend. Considering how many were sold, they're not that easy to come by in the UK for sensible money. I bought this 1977 example (made in Italy) for eight pounds in 2021, complete with original box and manual. And it works almost perfectly. The TI-30 was incredibly popular mostly because it was incredibly cheap, but it was pretty decent for the time as well as cheap. Texas launched the more luxuriously built and equipped SR-40 at the same time, at twice the 25 dollars the TI-30 cost, but the two calculators were really pretty much the same under the skin. Equivalent models from Casio, Sharp or Canon all cost at least twice as much as the TI-30 and the calculator everyone really wanted, the Hewlett Packard HP35, was four times the price and unobtainable for most students. Introducing a good-enough calculator at such a low price was a masterstroke. Incidentally, the UK price in 1977 (in the Argos catalogue) was £16.95 or about £110 in 2021 money. They did it by reducing everything to the bare minimum. The chip inside was the TMC0981 from a new family of scientific calculator chips. And as pioneers of using just the one IC for everything, TI crammed everything onto the TMC0981, which is the only proper component inside apart from the LED display. That chip does everything. Other scientific calculators of the time were stuffed with expensive to manufacture discrete components. The circuit board is tiny, only taking up the area around the display. The inside of the TI-30 is mostly fresh air, with just a very simple keyboard mechanism using metallic dome switches keeping the battery company. The keyboard itself, although it uses separate keys, is the cheapest possible with no printing or injection moulding to worry about. There are no screws holding the case together, just a series of snap-together tabs. It was unusual at the time to see buttons for on/off and deg/rad/grad rather than switches but this kept the cost down once again. They saved on power too. Many rivals (and the SR-40) used rechargeable battery packs and/or mains power, but the TI-30 used only a 9v battery as standard. It sits in a huge compartment only kept from moving around by ridges moulded into the underside of the compartment cover. It's a bit tricky to get that cover back on. There's a square hole in the right hand side of the calculator that looks a bit odd, but it's there so you can connect power to optional extras like a slot-in mains adapter or two different rechargeable battery packs, both of which fit into the large space the 9v battery doesn't fill. Other optional extras were cases in several colours. So it was the most bare-bones scientific calculator you could get, but you could option it up later, which was clever marketing. One thing they did include was a really good instruction manual that's still a model for how these things should be written. By today's standards the TI-30 feels slow, has a keyboard you either love or hate (I don't like keyboards with a firm click because they're hard on the finger-ends and force you to key things in slowly), and has only a bare minimum of functions. But it's an accurate machine (it calculates to 11 digits despite the 8-digit display), what functions there are are all useful, and the keyboard is very well laid out indeed. Texas kept virtually the same layout for decades on more modern calculators carrying the TI-30 name and for good reason. Mine seems to have just one little fault, which is that the minus sign in the ninth digit far left doesn't light up. In the photo you'll see two 'inverted commas' in the ninth digit, which means the calculator is in gradians mode – you get one comma for radians and nothing when in degrees mode, which is how it powers up. Note also how the display can show an 8-digit decimal by losing the leading zero when required, an unusual but clever feature. The display is deeply recessed and hard to see if you hold the calculator in your hand; it works best on a desk where the four rubber feet keep it firmly in place. I wouldn't want to use this as my everyday calculator, though I could, and I can't get dewey-eyed over it like some Americans seem to do, because Casios are still better, but you can't deny that this was a very significant and rather interesting model in the history of the electronic calculator. Box: Y Case: N Documentation: Y
Bought in 1981 My first scientific calculator, bought while at school, and indeed through the school. I never understood why schools preferred Texas Instruments calculators when Casios and Sharps were so much better. Slow (even a sin calculation takes over half a second, and factorials take forever) and crude with a terrible and unreliable keyboard, I soon replaced it with a slick new Sharp. Was still going in 2008 when last checked. Forensics test gives a poor 9.114640577 Box: Y Case: N/S Documentation: Y
1985 I'm not actually sure if this is the first or second version of this variant of the TI-30 series. If it's the second it was made in 1987 or later but there's no obvious difference visually and both are made, like this one, in Italy. I could take it apart to check the dates but don't want to risk damaging the floppy PCB these use. This was the follow up to the beige-coloured TI-30 III so perhaps should be the TI-30 IV really... It uses the same straightforward key layout and method of operation as the original 1976 TI-30 with LED display and the various very successful models that followed. It's designed to be a school calculator so is pretty basic in its looks and construction (the plastic moulding is actually really crude) but feels quite tough. It comes with a hard plastic case to protect it. Less good is that it takes two LR44 button cells, the replacement of which (or the leakage) can easily lead to damage of the flimsy internals. This one seems fine though and works well. The buttons don't click like older Texas models but they have a positive action that some love though you can't tap numbers in quickly like on an equivalent Casio – you have to be deliberate. The 8-digit display is quite clear but not very informative, only showing annunciators for deg/rad/grad and inverse. Overflows and errors bring up the full word 'Error' made from number segments, which is traditional for TI calculators. There's nothing to tell you something's in memory or that you've invoked the constant function, and the display can only show a 5-digit negative mantissa. It's not exactly fast either. I got this as part of a job lot in 2021 – I only actually wanted one calculator from the bundle I bought so you might say this was a bonus, but if you average the cost they were about £1.70 each. Box: N Case: Y (hard separate case) Documentation: N
Bought in 1984 Interestingly different scientific calculator fits inside a hard case (not shown). Really nice to use. Looks like it should have more than an eight-digit display but doesn't. The extra space is used to display functions like + and – and so on. Plastic has yellowed with age (though kept inside box) from original pale grey. Still working on original battery (one LR44) in 2020 when I removed it to prevent damage in the future.. This first generation of the TI-30 Galaxy was manufactured in Japan by Toshiba. Production was moved to Italy in 1987. Box: Y Case: Y (hard case) Documentation: Y
2021 I've been watching the highly variable price of this model for some time on Amazon; when it dropped to just £10 I bought one. I've been wanting to compare it with the similarly specified Casio fx-991EX I bought a year or two ago for £16. This model has actually been around since at least 2013 so is hardly new in 2021 but not much changes in scientific calculators these days. I've never been much of a fan of Texas Instruments calculators in the past so does this one change my opinion? In some ways it does. Like the Casio it's quite a large calculator, built out of tough plastic and with a hard case that clips to the back when you're using it. Unlike the Casio, it's quite unattractive. The keys have a good quality 'squidgy' feel to them, but I find the Casio's keyboard faster and more pleasant overall. The chromed keys aren't that easy to see. I like the rubber feet on the Texas to stop it slipping about on a desk; the Casio doesn't have those. The display, which has adjustable contrast, is, like the Casio's, not the brightest but that's typical of these large panels which are not backlit. It has four lines though, so shows a lot of info. It turns different colours, from yellow to blue to purple depending on the ambient light... Talking of light, this is described as being 'battery powered with light assist'. It houses a CR2032 lithium battery but you have to unscrew the back to get at it – the Casio has a little door for its battery for quick access. You need the battery for memory back-up mainly on these calculators. Some of the keys have several functions on them that you access by pressing them multiple times. This is one of the calculator's best features and makes it easier to use for some things than the Casio which generally needs a press of the 2nd-function key first. It's particularly useful for items stored in the memory – there are eight memories and assigning a letter to each just needs one or more presses of the button above the 'sto→' key. You can use those letters directly in calculations. The sin/cos/tan functions bring up the inverses on the second press and the hyperbolic and their inverses on the third and fourth press. Like the Casio you can choose between textbook style input and output using surds (TI calls it 'Mathprint') or 'normal' decimals. The key above the enter key toggles (the answer) between the two styles. The calculator can directly solve equations too (don't think the Casio can) and is generally a bit easier to use than the complex-feeling Casio. It sometimes feels a bit slower to process complex calculations though, and lacks the Casio's clever and unique QR code generator that goes some way to making up for the lack of graphing abilities. Both this and the Casio have an incredible array of pretty easily accessible features – choosing one over the other is just personal preference. My preference is to have both! Box: Y Case: Y (hard case) Documentation: Y
1978 This non-functioning TI-50 came 'free' as part of a job jot so I thought I'd include it here even though it's dead. Although this particular example was thrown together in Italy, the TI-50 model was the first slimline Texas scientific calculator made in the USA and used a TI integrated circuit unlike the previous models that used Toshiba silicon. Internally the calculator uses a single flexible printed circuit board (Flex-PCB) with the integrated circuit and a LCD-module. There's no soldering or use of screws in the calculator. This made it easy and cheap to make, but TI calculators from this period are not reliable or long lasting; most you see on Ebay are listed as not working, like mine. I have other similar models that have failed and there doesn't seem to be an easy way to fix them because of the plasticky internals. Even when fully functioning these are slow calculators with very poor keyboards (keyboard 'bounce' is a big problem) and a very simple and limiting eight-digit display, so it's no great loss. Note the unusual twin memories and the 'Constant Memory' that retains numbers in memory even with the power off, assuming you can get the power to come on... Box: N Case: Y (wallet) Documentation: N
1979* I bought this example in 2020 for a mere £1.20. It's in pretty good condition and has its original box, wallet case and two chunky manuals, one of which is an application library, because this is a programmable calculator, in a limited way – its non-volatile memory can record 32 key strokes. The calculator was listed as not working and I thought it might just be the usual problem of dirty battery terminals, but after much messing about with copper tape and so on, I concluded it really was not working. So I looked around for another and found one almost as cheap that looked rough and had no box or manuals. It was listed as untested and needed some work to get it working. I swapped the guts of that (PCB, display, keyboard membrane) into the case of the first one and it works well enough though the keys need a very firm press. *The one I bought first is dated '4779' (47th week of 1979) and the one I cannibalised is dated '0683'. The 1979 one has a TP0323-4NL chip dated '7940', which fits nicely with the '4779' stamped into the plastic on the rear of the case. Both were made in Italy. The TI-53 was introduced in August 1978 and lasted until 1985 – a very long production run. Compared to calculators like my Swiss-watch-like Panasonic JE-8433U from the same time, the internal (and external to some extent) construction of this Texas Instruments calculator is really cheap and nasty. There are no screws – everything snaps together and feels brittle and flimsy. The PCB is a floppy piece of plastic glued to a set of terminals on the sealed keyboard membrane. But the worst part is that the battery contacts are just little flexible 'ears' on the end of the plastic film PCB that protrude into the battery compartment. The unwary might not realise these have to be carefully placed on top of the batteries; if you put them underneath, snapping the battery door back on will likely break the contacts on them.It's no surprise that almost every time I see this type of TI calculator on Ebay it's listed as 'parts only'. It's not even as though it's a good calculator. By the time it had been in production for seven years, it must have seemed out of date – the limited function set and basic eight-digit display would not have compared well with models from Casio or Sharp. And it wasn't even cheap – my 1979 model has a price sticker on the box of £27.95 – over £140 in 2020 money! Box: Y Case: Y (wallet for 1979 model and hard case for 1983 model) Documentation: Y
Texas Instruments TI Business Analyst - II
1984 This example is dated '2284' so is one of the last ones made; the model was introduced in 1978 to replace the original version with a red LED display. It was 'assembled in the USA'. It's part of the 'slimline' range (see also my TI-50 and TI-53) and suffers all the usual problems of a limiting 8-digit display with hardly any annunciators, and a frankly appalling keyboard. I got this in a job lot I bought for one specific calculator (not this one) and didn't really expect it to even work. But it does work if you can put up with the keyboard. These were not cheap calculators, but a cheap Chinese calculator today puts them to shame in terms of internal construction quality. I'm not familiar with using a financial/business calculator's specialist functions but this clearly has some pretty powerful functions for the right user, and there's a smattering of the higher maths and statistical functions you'd expect to see on a scientific calculator. Power comes from two LR44 button cells that you have to carefully insert under two little flaps that are very prone to breaking. Box: N Case: Y (wallet) Documentation: Y
Texas Instruments TI-60 Programmable Calculator
Another Chris and Sue donation to the collection. It still has its hard case (not shown) but no box or manual. Condition is excellent. The Datamath calculator museum says: 'All other slanted calculators offer you a mantissa of 8 digits and 2 exponents, the TI-60 uses 10 digits to display either the mantissa or combine 7 digits mantissa and 2 exponents. The reason is the enhanced precision of internal calculations, here you get similar performance like the TI-62 and TI-65 of the Galaxy line.The TI-60 is one of the famous 'nearly programmable' calculators; you can store up to 84 key-codes in a permanent memory shared with the storage for the statistical calculations and user memory. Inside the calculator you'll find once again the two-chip design of most slanted calculators that allowed more features compared to the slimline series. Instead of the two TP0456-based chips of the TI-55-II you'll find here a TP0458 Master with a TP0456 Slave chip. The design of the TI-60 was changed in 1990 slightly; compare the printing below the bottom row of keys: • 1986: ADVANCED SCIENTIFIC • 1990: PROGRAMMABLE SCIENTIFIC' So this is 1990 or later. It performs very slowly by modern standards, and even by 1986 standards I'd say. An arc cosine takes several seconds. Box: N Case: Y (hard case) Documentation: N
Bought in 1984 Rather dull card sized solar calc. Box: Y Case: Y (wallet) Documentation: Y
Bought in 1986 Neat card sized solar model with big rubber keys. Box: Y Case: Y (wallet) Documentation: Y
Bought in 1985 Almost certainly identical to the Hanimex I also have, except for the garish graphics. Both are probably OEM rebrands. Box: Y Case: Y (pouch) Documentation: Y
Bought in 1986 Cheap and very basic calc with angled display and rubber keys. Display looks faded from this angle but is fine in use. Box: Y Case: N/S Documentation: Y
Bought in 1984 Basic but decent solar wallet calc. Texas Instruments' designs were all over the place when it came to compact calculators but this one is very attractive and minimalist. Box: Y Case: Y (wallet) Documentation: Y
Bought in 1984 Somewhat tacky gold trim and horrible keyboard, but otherwise okay slim model. The Datamath website finds this an interesting calculator and says it was made by Inventa, an OEM maker of electronics: 'We consider the TI-1755 SLR as an important milestone in the coopeartion between Texas Instruments and Inventa / Inventec - while many TI calculators from 1982 were just design variations of existing OEM calculators, introduced this TI-1755 SLR some "TI-ness" to the product line and most designs thereafter followed this spirit.' Box: Y Case: Y (wallet) Documentation: Y
Bought in 1987 Neat design has tiltable display and clings tightly to its magnetised wallet case (not shown). This is the second version of the TI-606 – the first has much larger solar cells. Box: Y Case: Y (wallet) Documentation: Y
Bought in 1985 Folding solar model with hard case and spacious keyboard but curiously small display. Texas Instruments' non-scientific calculators have had such random designs over the years that they often don't seem stylistically connected. Brands like Casio have consistent design elements that have distinguished their calculators for decades and give a much stronger brand identity. If this didn't say Texas Instruments on it, would you guess the brand? Box: Y Case: Y (built-in) Documentation: Y
A simple Texas mini desk calculator, that was introduced in 1984. Another kindly donated to the collection by Chris and Sue in 2019. Box: N Case: N/S Documentation: N
