1974 Sinclair Scientific Calculator Repair and Restoration | Hacker News Reader

1974 Sinclair Scientific Calculator Repair and Restoration

retrorepairsandrefurbs.com

67 pointselvis7017 comments

There's a wonderful online emulation and analysis of that calculator by Ken Shirriff:

http://files.righto.com/calculator/sinclair_scientific_simul...

(which was discussed previously https://news.ycombinator.com/item?id=6302364)

The ability of the designers to do more with less is reminiscent of Steve Wozniak's work on the Apple I/II and other projects

> […] the calculator uses Reverse Polish Notation (RPN) to input calculations, simplifying the hardware design but making it more difficult to use.

I would argue against this statement which I’ve seen many times. RPN is not more difficult to use, it is simply different from what people have been using for the last few decades. Not being used to an human-machine interface and having to learn it should not be confused with difficulty of use.

Someone used to vi/vim has all the ease in the world to use it, but it might take a newcomer more time to adapt.

RPN has a very natural data waterfall flow, especially when stacks can grow to multiple levels. Of course you don’t have a direct view of it, but it becomes second nature. You simply know what that the higher value in the stack is your previous result.

Exactly the same argument made about Lisp.

I think it would be easier for a child to parse Lisp with rainbow parens than learn all those rules of order of operation most students find painful.

I think these old arguments are moot: all of these entry methods are from having to write equations linearly for the 1950s / 1960s teletype era (including "algebraic"). They all require you to keep a stack in your head.

Newer calculators have "natural textbook entry", where they show the equation in mathematical notation as you enter it, so no stack required in your head. The entry method (shown linearly) for division is: <divide> numerator <down> denominator <right>. The keystroke count is lower than it would appear because you can leave out all of the right-most cursor keystrokes.

The method could be further generalized to eliminate the need to know about precedence on entry. For example ab(c+d+e)*f could be: <mul> a <next> b <add> c <next> d <next> e <done> <next> f. Visually it could show the order of operations either with precedence, or in some new way (perhaps text size changes to indicate order).

It's interesting to think how programming languages could look in the post-teletype era.

I find it endearing how instead of having constants such as pi and Euler's number built into memory and accessible from some key combination, the calculator just prints it on the case for you to manually type in. This is a fantastic example of early developments in affordable computing devices.

Also, RPN ftw!

I'm currently reading "Sinclair and the 'Sunrise' Technology", which has a section on the calculator.

They initially had problems with battery life, but took advantage of the fact that they could strobe power to the LEDs and chips without completely compromising functionality to reduce the power consumption by a factor of 100. That allowed them to use hearing-aid batteries.

Those melted hand-taped traces are wonderful. It's high technology, from a more civilized age. It's too bad that the best software for making those organic PCB layouts, TopoR, is super obscure (and I'm worried being basically defunct)

They are beautiful.

My intuition is they were drafted by hand and reduced repographically based on the age and simplicity…which I mention because a pencil and a scanner are still an option today.

You’re going to love this: https://mitxela.com/projects/melting_kicad

The cool traces caught my eye as well. It’s funny how they have a distinctly 70’s look (appropriate to the age of the calculator).

Early electronics were designed to be repaired, or many.

My father wouldn't buy anything he didn't think could be reasonably repaired. Hell--it was a selling point most people took for granted.

From tv sets to most calculators, and even early computers, most had schematics available from the company, and the boards were laid out with repair in mind.

My old HP 454a Oscilloscope was designed to be repaired.

I look at these old circuits and they are art.

I once heard an old Electrician say, "The art of our trade died when we stopped sweating wires."

I repaired a Casio fx-602p recently, by harvesting a chip from a broken one, one of the tqfp ASICs. Worth it because eBay price from Japan for a working one is $250. I'd like an fx-603p, but they are going for $350.

This is like the Casio version of HP-41- alphanumeric keystroke programmable with cassette interface.

No plastic heatstakes (unlike HP), but you're hosed if the flex cable to the LCD is broken.

One of the most impressive things recently is the guy who made replacement LCDs for the classic Radio Shack / Sharp pocket computers (they don't use flex cables). That a hobbyist can do this at reasonable price is a sign that we are living in amazing times.

https://www.tindie.com/products/halfbakedmaker/lcd-replaceme...

I started out programming on the fx-502p (the numeric only ancestor of the 602) and I had the cassette/music interface. IIRC the 502 had only 1 branch instruction - BNE.

> It’s difficult to describe how pretty the LED-segment bubble display on this calculator is – photos don’t quite do it justice

However the LED display was also the main reason why this calculator needed 4 AAA batteries (which I imagine didn't last that long), while later calculators with "boring" LCD display could run for years on fewer batteries. My father had an early electronic watch with an LED display, which had a button you had to press in order to read the time - kinda like a smartwatch...

So that's a fail, then; the broken calc stayed broken, and the working calc worked.

That calculator led me into a 40-year programming career! From building it came building a 6502 micro then self-taught assembler, Forth, and contract programming jobs (first one: a multi-user homegrown-networking accounting package in Forth for a UK water utility).

My ex-wife's little brother had one of these, and man it was a pain to use - Reverse Polish combined with some weired ways of entering numbers. Poor little guy (dead now, sadly) never got to grips with it, and to be honest neither did I - I was not into computing much in the early 1970s. But it impressed some of his school-mates, so not an entire loss.

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