eBay find: Sinclair calculator UNBUILT KIT - Page 1
Forum section: electronics / general

author: gnorm
author_rank: Newbie
timestamp: March 30, 2016, 01:15:11 am
content: For collectors:http://cgi.ebay.com/131764519118

author: amspire
author_rank: Super Contributor
timestamp: March 30, 2016, 02:08:19 am
content: My first calculator! Still have it, but it was really bad. It was fun though.In my first year at Uni, they were still teaching us to use slide rules because no-one could afford the HP35/45 calculators. I got this kit. What Clive Sinclair did was to take a Texas calculator chip that normally just did +/-/*/divide/% and reprogram if as a RPN scientific calculator. Because he had so little ROM, he made a lot of shortcuts. It was only accurate to about 5 digits, you had to type in the values of all constants. Mine had Pi and e printed on the front, but that front printing wears off in no time.The next year, HP started to bring out affordable calculators like the HP21C. TI also had good scientific calculators, and use of the slide rule disappeared completely. Never used the Sinclair again.Richard

author: SL4P
author_rank: Super Contributor
timestamp: March 30, 2016, 02:26:28 am
content: Send it to Dave, or record your own Tear Up' !

author: amspire
author_rank: Super Contributor
timestamp: March 30, 2016, 02:56:18 am
content: Quote from: SL4P on March 30, 2016, 02:26:28 amI found my calculator, and I just realized that that kit is obvioulsy the super advanced model compared to mine. I have a date code on my micro chip of 7424 and the one on eBay is 1977. Definitely snap it up - they don't make calculators like that any more.I will post some pictures of mine just to make everyone jealous. 100% Sinclair quality!

author: m100
author_rank: Regular Contributor
timestamp: March 30, 2016, 11:56:18 am
content: Hope no one builds it, that really belongs in a museum as it is.I still have one just like that somewhere round the house but no idea where. Mine came assembled. Really slow in operation and it kicked out heaps of RF. It was used for a year or two and then replaced maybe 1977/78 with a really chunky TI-58 (I think I know where that one is!)My first electronic calculator was a four function Rockwell sometime in the early 1970's can't recall if it was the 8R or the 18R, I think I still have that one tooNow using a TI-68 from the early 1990's despite a few vertical lines missing in the display due to a failure of the heat bonding on the flex pcb. Wish I could either fix it or get another.Away from home, on the android 'phone' that barely works as a phone I useRealCalc

author: amspire
author_rank: Super Contributor
timestamp: March 30, 2016, 12:41:10 pm
content: I have the original model of the Sinclair calculator, and apparently the whole program including logs, trig, floating point with exponent was all done in only 320 instructions - 320 instructions was all the ROM space the TI TMC0805 chip had. I think all the trig functions were done in 40 instructions.The whole reason that Sinclair could bring out a scientific calculator at about a fifth of the competitors at the time is that they managed to use such a basic chip that was designed purely for +/-/*/divide calculators.sin(1) takes 7 seconds. Everything is reduced to the bone, so to get the square root of a number, I have to take the log, divide by 2 and take the antilog. Probably takes about 10 seconds since the keyboard is not much good.At the time (1974) it was OK - a slide rule went to 2-3 places. The Sinclair went to 4-5 places so that really was a leap forward. Before calculators, if a slide rule was not accurate enough, we had to use books of log and trig tables. Very, very slow, but still a little more accurate then the Sinclair. Every new non-Sinclair scientific calculator that started coming out from 1975 could do at least 10 places, and so there was just no point in trying to use the Sinclair calculators or after 1975. I do not know why anyone would still be buying the new model in 1977.Obviously this "new" model from 1977 uses a chip with way more ROM then mine and there are more functions. Hopefully, many of the quirks of my calculator were corrected - such as not being able to do logs of numbers less then 1.0, and not being able to do antilogs of negative numbers. Things like this made it pretty hard to trust.I have a few HP calculators, but I quite like my HP49Gs - I have six of them. So Realcalc is not bad, but I use a HP49G simulator on my android.

author: ralphrmartin
author_rank: Frequent Contributor
timestamp: March 31, 2016, 09:19:09 pm
content: Wasn't this the one that got sin(0) or cos(90) wrong, or something like that? I remember a kid at school had one, costing about £50 way back then, and we were jealous until we realised it didn't work right. It was only a couple of years before that that I distinctly remember our physics teacher telling us that a slide rule was the ultimate symbol of virility...

author: tggzzz
author_rank: Super Contributor
timestamp: March 31, 2016, 10:11:43 pm
content: Quote from: ralphrmartin on March 31, 2016, 09:19:09 pmIt gets a lot more than that wrong. Logs of numbers under one are a well known one.It was a remarkable achievement for the time, being 95% cheaper than an HP35 and therefore the only affordable calculator with transcendental functions - even if they were no more accurate than a slide rules and less accurate than 4 figure tables.

author: mikeselectricstuff
author_rank: Super Contributor
timestamp: March 31, 2016, 11:02:38 pm
content: Interesting article on the codehttp://files.righto.com/calculator/sinclair_scientific_simulator.htmlAnd some comments from the author of the code on Hackaday :http://hackaday.com/2013/08/30/ken-shirriff-completely-reverse-engineers-the-1974-sinclair-scientific-calculator/

author: linux-works
author_rank: Super Contributor
timestamp: April 04, 2016, 06:45:03 pm
content: that guy, ken, sure gets around! I've seen his name dozens of time on many arduino projects. some of his code is quite useful. seems like a really cool guy (never met him but I keep running into his name time and time again for 'maker' style articles and projects).

author: chris_leyson
author_rank: Super Contributor
timestamp: April 04, 2016, 07:02:38 pm
content: Wow what a findI had one of those when I was in school, used it for a few weeks and then bought a real calculator, Commodore SR1800. Log and trig functions were a joke and I think it would get stuck in a loop if you divided by zero. The LED display eventually got used in a project.

author: MrSlack
author_rank: Frequent Contributor
timestamp: April 06, 2016, 09:18:25 am
content: Being Sinclair I'm surprised it even worked.

author: dmills
author_rank: Super Contributor
timestamp: April 07, 2016, 09:38:39 am
content: Anyone else remember his flat screen portable telly?The thing was CRT based, with the beam bent thru 90 degrees by means of a permanent magnet to make the tube really shallow, amusing physics but the battery life was predictably awful.Or his class D audio amp kits of early 80's vintage, filterless and not in a good way....Regards, Dan.

author: MrSlack
author_rank: Frequent Contributor
timestamp: April 07, 2016, 09:53:34 am
content: Quote from: dmills on April 07, 2016, 09:38:39 amI saw one of those and was predictably worried about it when it turned up on the market. My television at the time was a hand-me-down Sinclair portable non-bent CRT, the MTV1 that my parents didn't use, because, well it sucked. It used electrostatic deflection rather than magnetic. I spent hours watching it with strained eyes waiting for it to blow up so I could justify using the CRT for a home made scope. When the time finally came, which was a matter of waiting for *any* Sinclair product, I cracked it open and yanked the chassis out and it was CRIMINAL design throughout. Sinclair managed to innovate in only one area: cost cutting. Unfortunately it wasn't designed to be repaired or fail safely and I found out that it had burned out the heater in the tube. When that went pop it took the rest of the power supply out and half the rest of the boards as it appeared that the load of the heater was required to keep it semi-stable... I reckon the flat CRT would have lasted less time!As for his amp kits, they were another remarkable innovation of minimal part counts. Every safety and reliable biasing feature was removed. If you liked toasting your speakers or gobbling up transistors then they were a good investment. Again, my first amp was a hacked up Sinclair Z50 someone had badly assembled and enclosed that I bought at a jumble sale for 10p which I added thermal shutdown (required for those bits of junk!), relays on the output and used some car speakers in some discarded speaker enclosures I found in the street. Plus I made it slightly less lethal by adding some earthing...Actually when I think about it, if it wasn't for his crap I probably wouldn't have as much interest as I do in electronics now.