EEVblog 1571 - Nobel Prize Winning Mailbag. 121GW, Retro calcs, Assembly, and Discrete Logic

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00:00 - Mailbag
00:18 - Barry Marshall, Nobel Prize Winner returns a faulty 121GW :-(
02:54 - Nobel Prize Chocolates
03:53 - Faulty 121GW
09:04 - TI SR-51 calculator from 1974
19:55 - TI SR-51 Teardown
25:15 - Digi-matic 8 calculator from 1972
29:47 - More retro calulators and assembly programming book
32:29 - Lean Multi-Platform Assembly Language Book
35:53 - Casio SL-760 credit card calculators + Sanyo
37:47 - Gent LC-517 wallet calculator
40:04 - DIY Scrabble Timer project using all discrete logic

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#ElectronicsCreators #Mailbag #retro

[samjones]

I believe that old calc was sent because it was one of the first hand calculators in the world. The Pocket/Hand Calculator was invented in Canada.

[FranLab]

I've got those individual 7-seg bubble displays, did a demo years ago - but I think that the number of digits and the dim display and the piggy backing add up to the fact that the on-chip drivers were current limited to Muxing a fraction of those displays so they doubled them up and even then had to current limit the segments to a fraction of full brightness.

[chongli]

I really love that scrabble timer! Discrete logic, 2 board design with board-to-board interconnects! Wow, thing of beauty!

[dosgos]

That Scrabble timer teardown was the surprise of the week!

[Penfold]

The stacked chips in the TI probably have 1 chip select line with differing active high / active low.
A real PITA replacing old ROMs with EPROMs when you can’t be sure how it’s CS lines work

[lesliefranklin]

Long ago, I had a Texas Instruments SR-52. It featured a magnetic strip reader/writer. There were separate libraries of programmed strips along with accompanying detailed description book. You could also write your own function library and record it on a blank strip. The calculator also came with a thermal printer.

[daveturner]

I really liked the scrabble timer for using discrete logic chips. We all need to remember how we got to where we are.

[ordulf]

Apparently, you have to go to Stockholm, Sweden to the Nobel Prize Museum to get the Nobel medal chocolate.

[ТарасКорж-гт]

Besides the R12:
R?4 was clearly removed manually. R?4 is across the orange capacitor from R12.

[Chriva]

Used to be such an honour to get waved at by Carl and family when traveling through the canals at our summer place back in my youth. Kinda sad how times have changed.
He's a very humble man

[bertblankenstein]

The Texas I struments SR-51 calculator: you are running it at 3V, but it looks like there is room for 3 AA cells, so i believe you are undervolting it. The stacked ROM (?) chips do not have to be identical and perhaps there is some internal address, or perhaps they have different chip select pins. I am 100% in agreement that is seems unusual, and it would be WAY easier to breakout a select line. Lastly at 24:44, is that a broken trace below the display? Maybe the unvolting is causing that counting thing.

[ymirthefrostgiant]

Optostic is pronounced opto-stick. These were used in many calcs at the time and were a high quality display. As the ad you found shows, they are still respected today. Few people know what's hidden inside these almost forgotten old bangers.

[cemx]

I was in engineering school from 1971 to 1975. Started with a slide rule. I had both a normal one (Post I think) and a ROUND one (no way to calculate off the end of that slip-stick). Freshman year one guy on the dorm floor had a four-banger. WOW! By the end of college EVERYONE had a fully scientific calculator. Mine was a TI something (51?). There was a 100 level course all the engineers had to take to learn how to use a slide rule. (WHAT? They didn't learn in high school??) Fast forward 4 years and the course was taught with HP-35's.

[michaelhull]

"Of course you could do this with a single micro" but look at all of those chips for 'just' discrete logic... an awesome build, just for fun and FAMILY!

[DavidLindes]

Is that a bridge across two of the middle-ish pins on the left edge of the main IC on screen around 7:30??

[WacKEDmaN]

nice to see Keiths new book!.. ive been following his ChibiAkumas channel and using his site and code for programming z80 ASM...ChibiAkumas is pritty cool.. its like a framework of sorts of z80 assembly that can compile on differnt systems, you can use it for making anything from a simple print..to a full game.. the nice thing about it is Keith explains how everything works and documents it beautifully.. ..his new work/book introduces non z80 based systems...
...love how ya almost called that calc a SR-71 Dave!...

[Enigma]

Yes, I wore my "slide rule calculator" on my belt during engineering school just like all the good nerds did!

[romancharak]

I remember buying things from Simpson's, when I was a lad . They were a very nice Department Store, which was the main competitor of Eaton's, another big Department store. Both stores had fabulous Christmas displays in their huge, street-level windows.

[Noneofyourbusiness]

The TI SR-51 was released in 1973 with an original retail price of $224.95 equating to $1, 555.53 in today's US dollars according to the CPI, so actually much more. You would have been one baller engineer with one of those back in the day. I would have worn it on my belt with pride.

[MrCarGuy]

The Scrabble timer needs a transparent case because otherwise you can't fully appreciate it!