Happy birthday, Sinclair Radionics: We'll remember you for your revolutionary calculators and crap watches

In 2021, it was 60 years since the founding of Sinclair Radionics, a forerunner of Sinclair Research and responsible for some nifty calculators and a not-so-nifty watch. The company was founded by Clive Sinclair, then a mere 20 years old, in July 1961. Its first product was the Sinclair Micro-amplifier for hi-fi systems, which …

[David M]

Sinclair Cambridge

I still use my Sinclair Cambridge calculator. The power switch is a bit dodgy, so it has a tendency to cut out mid-calculation, but that just adds to the excitement.

[werdsmith]

Re: Sinclair Cambridge

Working Sinclair calculators go on Ebay, £20 - £30, and can be up to £50 in good nick with packaging.

[Trigun]

Re: Sinclair Cambridge

Got one myself: I think it's a type 3 as it's got the two C CE and K buttons at the top and the PCB traces inside the battery cover compartment look like those on a type 3.

Is this where I find out it's worth a small fortunate? :D

[Martin]

Re: Sinclair Cambridge

Mine, sadly, has long gone. I remember a friend of mine buying one for thirty quid in about 1972, and saying "That's an amazing price - they won't go much cheaper than that." I bought one a year later, and the price had dropped to £18, and I remember thinking "Ha - that showed him. Thirty quid? But still, £18 is a fantastic price, they won't go much cheaper than that..."

Of course, ten years later, 4-function calculators could be picked up for £1.99.

My father actually adapted mine to allow you to plug in a cheap power-supply (sort of thing that was used for transistor radios). A mains-powered calculator!

What amused me about the Sinclair Cambridge was what happened when you divided by zero. Error code? Ha! The display just rapidly ran through numbers until you pressed clear. I used to experiment by dividing by very small numbers - you could get different speeds of display changes...

[Flywheel]

Re: Sinclair Cambridge

Aha! Your name is Rishi Sunak and I claim my £10

[werdsmith]

Sinclair actually launched two monochrome mini TVs, the MTV1 in 1977 was a miniaturised conventional CRT with cathode behind. The FTV1 (TV80) came along in 1983 and had an amazing CRT with a sideways electron gun, to a shrunken screen that was then made conventional format using a lens. It also used a flat pile battery from a polaroid camera. Sony and Panasonic also did a CRT pocket TV, but Casio came along with LCD and blew them all away.

[heyrick]

"Sony and Panasonic also did a CRT pocket TV"

The Sony Watchman with its 1 inch CRT was actually high enough resolution that I could power it up under the duvet (to not bother anybody else in the dormitory) and read the teletext carousel that used to be on BBC2 in the early hours. Well, it was something to do if I couldn't sleep. Just had to keep my ears alert for matron doing the late night round, because if she caught me I'd have something else to do that was much less enjoyable...

[Yet Another Anonymous coward]

> ears alert for matron .... because if she caught me I'd have something else to do that was much less enjoyable...

Mind = Boggled

[Steve K]

Oooh Matron!

Ooooh Matron!

[Anonymous Coward]

Personnally, I went blind at that age....

[Anonymous Coward]

Were the Sinclair TVs used for the funky video communicators in Space 1999?

[werdsmith]

Were the Sinclair TVs used for the funky video communicators in Space 1999?

The Space 1999 Commlock props were based on Panasonic TR-001, incredible device for 1971, but shockingly expensive. Sony Watchman can be seen in Rain Man.

.

[Red Ted]

Sinclair MK14

Significantly there was the Sinclair MK14 in there too between the watches and the ZX80.

[Anonymous Coward]

Re: Sinclair MK14

The Register covered some more about the gap between the watches and the ZX80 here:

https://www.theregister.com/2014/01/16/archaeologic_ian_williamson/

It discusses the MK14 too. (I know all this isn't Sinclair Radionics, but it's a bit of an insight for some of us into 1970s business and entrepreneurship in the UK).

[steelpillow]

Re: Sinclair MK14

Technically it was the Science of Cambridge Mk14, that company being Sinclair's first bolt-hole from the NEB. It had the world's first membrane keyboard, which needed occasional dustings of talc to keep working, and an optional tape interface add-on that I never could get to work.

Practical Computing ran my first-ever published article, on building one.

I also recall the fun game of setting the Enterprise to divide by zero and watching it flatten its batteries as the LED display tracked in real-time its attempt to approximate to infinity.

They don't make nostalgia like they used to. C5 re-engined with rare-earth magnets in its motor and a lithium battery, anybody?

[Headley_Grange]

Calculator

I've still got my Cambridge Scientific calculator. The power switch went a bit dodgy after only a couple of months, but it didn't deteriorate any more after that and the calculator is as good as it was in the 70s when I got it. Mine must have been a second version because my mate got one a few months before me and the numbers wore off the keys of his after a year or so, which has never happened to mine. I remember it being a battery hog and having to use alkaline batteries, which were quite expensive on paper-round money!

Replaced with an HP-11C when I got my first job - which is also still going strong and runs for ever on 3 button cells.

[Warm Braw]

Re: Calculator

the calculator is as good as it was in the 70s

I spent about a day walking the length of Tottenham Court Road to get the best price for mine. In typical Sinclair style, they cut just too many corners: an essential skill was to know when the result was going to be ludicrously wrong and revert to your log and trig tables.

[MyffyW]

Re: Calculator

"In typical Sinclair style" - cheap black plastic, beige and brown polyester?

[H in The Hague]

Re: Calculator

"Replaced with an HP-11C when I got my first job - which is also still going strong and runs for ever on 3 button cells."

I got my HP 20S over thirty years ago, still works and still on its original set of batteries! (Admittedly I don't use it that much.) Now that's proper engineering and product design.

[WhereAmI?]

Re: Calculator

Can't quite beat that. I have a Casio fx-83WA bought just two decades ago and is on its third set of batteries. It saw me through three years of college (I'm not that young - I went back full-time in my Forties). As above, doesn't get too much use these days but is always there when needed.

[IGotOut]

Oddly...

The c5 probably would be a bigger success now. Far safer than a death trap electric scooter, but not as "safe" as a ebike.

[werdsmith]

Re: Oddly...

Clive's nephew tried to make a go of it in 2017. Didn't go anywhere.

[MyffyW]

Re: Oddly...

Turn the wheel configuration the other way round (two at the front, one at the back) and you're probably onto something.

[Phil O'Sophical]

Calculator emulator

I built my Sinclair Scientific from a kit (thanks Mum!), it still works. If anyone wants to see what it is like, have a look at this great piece of reverse engineering by Ken Shirriff.

[Alan J. Wylie]

Don't forget the multimeters

radiomuseum.org page.

I've still got my PDM35. I built myself Sinclair Scientific calculator too, but sold that on when I got myself a Texas Instruments SR51A

[Tom 38]

Rubber keyed ZX spectrum was probably the first computer I ever used, and definitely was the first computer I wrote a program on. To me (and probably many others in the UK), calling it "life changing" is a massive understatement.

[Will Godfrey]

Same here... and it wasn't even mine. I was asked to fix it by a friend (failed transistor in the regulator) while he was on holiday.

[Gotno iShit Wantno iShit]

And here...

Friend of a friend had a ZX81, I was utterly hooked first by 3D Monster Maze and then the amazing process of typing in a program to make it do other things. I was too young to consider writing a program, playing one was far more interesting. My career can be traced back to those heady summer days lying on the carpet praying the RAM pack didn't fall off again.

[Andy The Hat]

Don't you just hate how young some people are!

[Andy Denton]

Not sure why all the panic.....

NEC 7805 IIRC. Mine failed on my Issue 3 Spectrum. I can remember walking into Maplin and asking for one and the guy behind the counter said "Broken Spectrum?" - seems it was a common issue.

[Eclectic Man]

Sinclair pocket calculator

A friend in the 6th form had a Sinclair calculator. We were doing 'A'-level maths and he got it out to calculate the square root of 36 (which I knew to be 6). The Sinclair gave the answer 5.9999999999.

[Stumpy]

Re: Sinclair pocket calculator

It's because the early calculators didn't actually have a square root function properly programmed either in their software or in the hardware. Instead they used Taylor Polynomials to approximate the answers so would always be slightly off when it came to rounding to a fixed number of decimals.

Taylor expansion for sqrt(x)

[dajames]

Re: Sinclair pocket calculator

The Sinclair gave the answer 5.9999999999.

If you're talking about the Sinclair Cambridge Scientific it only had an 8-digit display so you wouldn't have got that many '9's. A friend of mine had one, too, and my recollection (possibly clouded by time and beer) was that when you asked it to do something really esoteric like a square root or a trig function it only deigned to give you six digits.

Still, even five nines was pretty good, back then! The HP35 would do better but cost and order of magnitude more (they were advertised in New Scientist, and I recall wanting one so very much ... but not at that price!)

[Headley_Grange]

Re: Sinclair pocket calculator

I just dug out my Cambridge Scientific.

SQRT(36)=6

SQRT(2)=1.4142135

SIN(52 degrees)=0.78801

The trig functions are truncated to 6 digits but others aren't. It takes 2.2 secs to do the trig function, but the square roots are instant.

[dajames]

Re: Sinclair pocket calculator

The trig functions are truncated to 6 digits but others aren't.

Apologies -- time and beer, as I said.

[Stoneshop]

Still, even five nines was pretty good, back then!

Even today, companies are trying for five nines and coming up short.

[Ian Johnston]

Re: Sinclair pocket calculator

The Sinclair scientific calculator also notoriously could be 30% out on trigonometric functions.

[Dan 55]

Re: Sinclair pocket calculator

I tried the emulator mentioned in a post above and followed page 23 in the manual which explains how to get square roots, it's linked to in the grey boxout on the emulator page:

36 E 1 ▲ x (log)

2 ÷

▼ × (antilog)

And got 6.0004.

Maybe there were different ROM versions with with slightly different accuracies. Whatever the reason, Scientific seems like the wrong name for this thing.

[Headley_Grange]

Re: Sinclair pocket calculator

5.9999 on my Cambridge Scientific

[Dan 55]

Re: Sinclair pocket calculator

So is that 6 (a few posts above) or 5.9999?

Either way, a Sinclair Cambridge Scientific isn't a Sinclair Scientific. There's no square root key on a Sinclair Scientific.

[Headley_Grange]

Re: Sinclair pocket calculator

It's a Cambridge Scientific - white. I didn't know there was a different one just called Scientific - sorry for any confusion.

For clarity, I was replying to two different posts.

SQRT(36) = 6

e^(ln(36)/2) = 5.9999

[keithpeter]

Re: Sinclair pocket calculator

@Dan 55

Beats a slide rule and quicker than log tables (both of which I have used)

[Anonymous Coward]

Re: Sinclair pocket calculator

> The Sinclair gave the answer 5.9999999999.

Liar. It didn't have that many digits!

[Headley_Grange]

Re: Sinclair pocket calculator

I think it's a bit harsh to call someone a "liar" because they mis-remembered something from over 40 years ago.

[Spanners]

Re: Sinclair pocket calculator

They had a brilliant way of stopping people "borrowing" them - Polish Notation!

[Peter Gathercole]

Re: Sinclair pocket calculator

It's actually "Reverse Polish Notation" (RPN).

Most early HP calculators used it, and it used to confuse the hell out of people who were looking for an "=" key.

If you use something like "realcalc" from the Google Play store, you can select RPN as the calculator type to have a play.

[Anonymous Coward]

Re: Sinclair pocket calculator

I never had one of these Sinclair calculators (Prinztronic Scientific Mini was what I had, then a TI57) but what I read at the time said the Sinclairs used some "modified" flavour of RPN rather than the proper RPN used by serious HP calculators. Not that it matters much now, but...

[JulieM]

Re: Sinclair pocket calculator

Rounding errors are far from new. If you use a book of four-figure log tables (such as Frank Castle's "Logarithmic and Other Tables for Schools") to multiply two by two, you will get the answer 3.999.

I am always nervous about using log tables since I learned of the possibility of publishers inserting deliberate errors as canaries for plagiarism. What would happen if somebody designing a bridge inadvertently landed on such a deliberate error, and the bridge ended up collapsing?

[Robert Moore]

I want a C5

I know, I am strange.

I really want a C5. Strangely they are stunningly expensive theses days. At least by the time it is shipped to me in the west coast of Canada. (Where it would fit right in.)

I do believe if it were released today with a modern motor and battery combo it would probably be successful.

[Headley_Grange]

Re: I want a C5

Are you sure? Is it hilly where you live?

https://www.ebay.co.uk/itm/Sinclair-C5-Sinclair-front-brake-caliper-assembly-039-ready-to-fit-039-/203458141961?hash=item2f5f0cdf09%3Ag%3AVwUAAOSw-7ZgpBin&nma=true&si=Bj4e7d8UCb8EHx71QhiLbPWdr2E%253D&orig_cvip=true&nordt=true&rt=nc&_trksid=p2047675.l2557

[werdsmith]

Re: I want a C5

I do believe if it were released today with a modern motor and battery combo it would probably be successful.

Nah.

https://www.theengineer.co.uk/sinclair-c5-revamped-by-sir-clives-nephew/

[Dan 55]

Re: I want a C5

According to the website it's still on pre-order... and on the same website you can find you can find Raspberry Pi gaming cases.

So, still the the same crazy mix of products in the family tradition.

[John Brown (no body)]

Re: I want a C5

"I do believe if it were released today with a modern motor and battery combo it would probably be successful."

Not sure about Canada, but over here, we call the modern incarnation "mobility scooters"

[Martin an gof]

Re: I want a C5

I do believe if it were released today with a modern motor and battery combo it would probably be successful.

We have two at the museum - one "accessioned" as it was built in Merthyr so is sat on a pedestal with "do not touch" labels - the other bought from eBay a few years ago so that people could have a go.

Mostly they enjoy it but steering is a bit odd, the brakes are really rubbish, the chain keeps falling off the idler, and in order to save on a differential just one rear wheel is driven by the pedals, with the other single wheel driven by the motor, so it's rather lopsided. Our eBay version doesn't have a battery any more, but the "go" button is "on/off" so I'd imagine it'd be quite difficult to control at first.

The other big downside is that the seating position is not adjustable, so unless your legs are within a certain range of lengths you will either find your knees in your chin or be unable to reach the pedals.

And it's always worth warning anyone wearing a skirt that it's not the most elegant of machines.

If you're looking for something safer and more practical, there are several machines along the lines of the Renault Twizy, but they're not cheap - the C5, as well as being made on a spare production line in a washing machine factory, cost about the same to buy. My calculations suggest the entry model Twizy could buy you perhaps 40 reasonable-quality washing machines.

M.

[Sam not the Viking]

Sinclair Matchbox Radio

In 1967 (?) I bought a Sinclair Matchbox Radio in kit form as an improvement to the crystal radio I had made. I wanted better reception of Radio Luxembourg when I was supposed to be asleep. I failed on the construction, my soldering has since improved, but when it did work it was quite the novelty. The best reception for Horace Batchelor.... don't tell me you don't know K-e-y-n-s-h-a-m......

[Persona]

Re: Sinclair Matchbox Radio

I built one of those in 1967 or 1968.

I didn't have an electric soldering iron so all the soldering was done with the smallest plumbing soldering iron I could find that I had to heat on our gas cookers hob.

[adam 40]

ZN414

Wow - that reminds me - I used to build my own matchbox radios using the ZN414 back in the '70's.

But - I did have a soldering iron.

[wishis]

Watch out

I inherited one of the Sinclair watches and it is in working condition, although not tested the battery life....

[Flywheel]

Re: Watch out

I still remember the ads .. "The Black Watch.. blah blah .. no unprofessional buttons - just touch the front panel to show the time". Available in kit form, so my teen sausage fingers deftly assembled it, and with some effort managed to squeeze it all into the case. It was only then that I realised that pushing the primitive "touch" buttons meant that all the innards would pop out of the back of the watch case as well.

Happy Days .. not.

[scottyctalk]

Seems like another good opportunity to post this brilliant piece of work.

https://youtu.be/Ts96J7HhO28

[grumpyoldeyore]

A watch that doesn't display the time until you do something ?

It'll never catch on ....

https://help.fitbit.com/articles/en_US/Help_article/1744.htm

[Eclectic Man]

Re: A watch that doesn't display the time until you do something ?

At a maths conference (in the 1990's I think) I saw my first ever solar powered wristwatch. It had an LED display that only lit upon when a button was pressed. Most of the surface was two solar panels. I have no idea how accurate it was, but as you had to press a button that meant using both hands to tell the time. One of the American genius logicians was wearing it and showed me.

[J.G.Harston]

Re: A watch that doesn't display the time until you do something ?

You need to move your sleeve out of the way to see your watch anyway, so your hand is already there, it's an insignificant modification of the action to also touch the watch.

[werdsmith]

Re: A watch that doesn't display the time until you do something ?

Long sleeves? Not on my arms.

[PTW]

Re: A watch that doesn't display the time until you do something ?

Unless you have really short arms/long shirt sleeves, I find an action akin to shooting your cuffs enough to reveal my wrist watch, no need for my other hand.

[Anonymous Coward]

Re: A watch that doesn't display the time until you do something ?

I did have one - although it had a battery as well as the solar panel.

I knew when to change the battery when it started displaying the time as 13:72 (not 24 hour display)

[Anonymous Coward]

Re: A watch that doesn't display the time until you do something ?

We had LCD ones back in the late 1970's. Solar powered watches. No buttons required. Pretty sure I got my first one in 1979/1980. A Seiko I think.

Back when I thought digital watches were a really neat idea.

Been analogue since 1993. Same watch, still tickling strongly..

As for Sinclair kit. Had the Scientific Calculator with the batter bulge. Replace with an all singing all dancing Commodore calculator. Was given a Spectrum as a present. Never used it, my brother got it. Only used real commuters, with real keyboards. None of these rubber johnnies..

[AnotherName]

Other earlier hardware

Sinclair used to do a range of modular slimline 'HiFi' kit in black with transparent perspex slider controls, meant to be mounted onto a piece of furniture. Used to be advertised in all the electronics mags back in the 70's.

[Fred Dibnah]

Re: Other earlier hardware

That was the Project 80 system. I had the stereo FM tuner, mounted on a die cast box containing the power supply. It was really hard to tune into a station using the slider, and the stereo separation was poor. It also had a tendency for the tuning to drift as it warmed up.

[Persona]

Re: Other earlier hardware

My friend had one of those Project 80 systems.

The amplifier was labeled as "short circuit protected" and it was ....... however the day he accidently unplugged a speaker the open circuit made the power transistor go bang.

[JulieM]

Re: Other earlier hardware

That is because the voltage of a badly-designed power supply, especially one using an old-fashioned steel-cored transformer, and even more so one using a cheaply-made transformer, is very load-dependent; and without the leakage current flowing through the loudspeaker and its coupling capacitor, the voltage can rise above the PIV of the collector-base junction of one or the other output transistor and start it conducting when it should not be.

[Anon]

Faster!

The Sinclair Cambridge Programmable Calculator might have been the last electronic device that I could multiply two double-digit numbers faster in my head than by typing them in and waiting.

[Dan 55]

Later companies

Afterwards he was involved in the Z88 portable computer, wafer-scale integration, and cordless telephones. Each in their own individual company maybe to limit exposure to failures and each successful at least for a period.

Then as usual he went and burnt profits on his electric vehicle obsession. If weren't for those and the portable TV and watch failures he'd probably have had an empire.

[John Brown (no body)]

Re: Later companies

Not forgetting probably his biggest failure, the Zike

[Anonymous Coward]

Re: Later companies

Thurlby? Thandar?

[Steve Graham]

A browse of that Planet Sinclair site reminded me that I had a Cambridge Scientific Programmable, a calculator watch (which worked: seems I was lucky) and an original Spectrum.

I also pulled a BT Tonto out of a skip in Martlesham Heath, but I don't think I got it to work.

[J.G.Harston]

The amazing thing about it was the scientific constants weren't stored in ROM, but stored by printing them on the case!

[Ian Johnston]

That bargain £80 (+VAT) was, according to the Bank of England inflation calculator, the equivalent of a cool £1200 today.

[Anonymous Coward]

Exactly.

Back around that time I wanted a calculator, but at that price there was no way my dad would buy me one. It was a ̶s̶m̶a̶l̶l̶ fortune back then.

But less than a year later the prices had fallen so much I got one as a Christmas present. A Casio, which still works perfectly today (green fluorescent tube for the display). It changed my life as far as maths at school was concerned, and ours was the first year in which the calculator could be used in 'O' Levels.

[RLWatkins]

I missed, and miss, the QL.

And that was a shame. At the time the 68000-line of CPUs would emulate a PC faster than a PC would run. Saw a lot of potential, but it just didn't catch on.

These days one can use a handset to do what once required a desktop computer: mirror it to a TV, pair a Bluetooth keyboard and mouse, and you can do word processing or coding or watch movies in a hotel somewhere on I-40.

The QL would have given us similar capability, at least similar for its time, back in the early 1980s, only it didn't catch on so the software and storage didn't develop.

It would have been a game-changer. Que lastima.

[Anonymous Coward]

Re: I missed, and miss, the QL.

Sorry to burst you bubble but in 1984 I worked in a place where we had the same software running on Victor 9000's / Apricots, QL's and 128K Mac's. The QL was an also ran. Not even in the running. Add to that its shoddy manufacture, it's held together by string and chewing gum design (later revs were mostly fixed), and the total fantasy world Uncle Clive lived in and it was obvious to all involved the QL was a fiasco. At any given time about half the QL's in the office were inoperative and my abiding memory of the Sinclair QL is partly dissembled machines sitting on desks in various states of triage surgery.

In 1984 the Macintosh was a game changer. The IBM PC/AT was a game changer. The QL was just the punchline to a joke. A bit like Lucas Electrical and the British car industry of the 1970's.

[DavyPaul]

Re: I missed, and miss, the QL.

ISTR that the QL was packed into the BT Merlin Tonto and the ICL OPD (One per Desk) integrated computer and telephone?

https://en.wikipedia.org/wiki/One_Per_Desk

[Anonymous Coward]

Re: I missed, and miss, the QL.

Yeup, OPD was a QL with a phone stuck on the side. All the same problems as the QL but I seem to remember the cases were a bit more robust so less likely to fall apart. Still the same internals problem so I dont think I ever saw an OPD fully assembled except at demos.

I think the word that best describes the QL was shoddy. Although by the time they did the final clearance sale what was coming out of the factory was actually pretty good quality. But by then it was far too late. The market moved very fast back then. What was wow in 1984 was a big yawn by 1986. I sat down with my first 128K Mac in Jan 1984 but by December 1986 I had a Mac II sitting on my desk driving two Sony monitors with 4 meg of RAM and two 20Meg HD's. And two years later the same set up was one quarter the price.

[davcefai]

Nostalgia

At school in 1964 I helped the science teacher to build a stereo system around a BBC studio Tape Deck and a Sinclair set of apmlifier, preamp and speakers.

The sound from the Sinclair kit was, for those days, astounding. The Rector suspected that we had spent well over our budget!

When I got to Edinburgh in 1973 the first thing I bought was a Sinclair Cambridge calculator. They were so new that at examination time the Heriot Watt University Senate ruled that while Slide Rules were OK we could not use calculators in our exams as they would give their owners an unfair advantage. Only 2 out of 14 in the course owned a calculator.

[Antony Shepherd]

I had a Black Watch. Actually, I had several.

It'd work fine for a few months, and then one day you push the button and it shows you the time is something like "47:89".

Send it back to Sinclair, then a few weeks later another one arrives. It works fine, then one day... and so on.

Think I got through three or four before i gave up and bought a Casio.

[Big_Boomer]

I had a Cambridge Scientific, a Black Watch, a ZX81, and a QL. I learned to do complex maths on the Cambridge, to not rely on the Black Watch <LOL>, to code in BASIC, Assembler and eventually Z80 Machine Code on the ZX81, and did some 68000 assembler coding on the QL.

Everything Sinclair made (with the possible exception of the Cambridge calculators) needed modification and upgrading. The ZX81 benefitted massively from a bigger heatsink and bolted down memory extensions. The QL benefitted from 3½" disk drives, more RAM, and a better keyboard. I never owned a Speccy but those friends that had them hated the keyboard and the constant crashing.