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

[@samjones1954]

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.

[@2oqp577]

As a matter of fact, I was given the calculators by a Amateur Radio guy that made me promise I'd sent them to Dave. The deed is done! :-)

[@jfwfreo]

Texas Instruments actually made the first ever hand-held calculator.

[@samjones1954]

Guess I was wrong. I heard as a kid that the Canadian government scientists had made the hand calculator. I am now betting that they made one, not the first one, but it is probably the one that is shown on this video @@jfwfreo

[@radman999]

Also Commodore was a Canadian company as well. They sold many a calculator and office supply. I still have Made in Canada Commodore filing cabinets. Yes, that Commodore.

[@barrybogart5436]

Actually, a Canadian company DID invent the first microcomputer around the same time: en.wikipedia.org/wiki/MCM/70

[@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.

[@simontay4851]

Well then why not use transistors or transistor array ICs to drive the segments at full brightness.

[@Penfold42]

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

[@user-lo8gq3pr6e]

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

[@theriddick]

yeah looks pretty suss in that area

[@lesliefranklin1870]

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.

[@chongli297]

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

[@ordulf7193]

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

[@dosgos]

That Scrabble timer teardown was the surprise of the week!

[@daveturner5305]

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

[@bertblankenstein3738]

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.

[@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

[@EEVblog]

Carl?

[@Chriva]

@@EEVblog Our king. He's more a beloved people symbol than actual ruler tho. Nothing like it is over in the UK where the monarchy still have power.

[@Chriva]

You're handed the Nobel Prize by him during the ceremony. Just realised some people may not know that. Doh!

[@MattyEngland]

​@@ChrivaThat's the opposite the British king then. Everyone knows Charles is an inbred WEF kiddie fiddler! Best friend of Jimmy Savile and brother of Epsteins best mate! All just a terrible coincidence though obviously.

[@Spookieham]

​@@ChrivaKing Charles has no power whatsoever. Parliament can remove the Monarchy tomorrow if it wishes. Do your research.

[@cemx86]

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.

[@chitlitlah]

I wasn't born until a decade after you started engineering school, but I love slide rules. I'd never seen one until about 15 years ago when my cousin gave me one he found in a house he'd just moved into. I researched how they work and it's absolutely brilliant. They're not precise compared to a calculator, but you can do a lot of different mathematical operations within a few seconds just by sliding it back and forth. It's been a while since I played around with it, and that's exactly what I'd be doing now if I wasn't away from home.

[@michaelhull7873]

"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!

[@jaro6985]

The micro is hidden under the LCD and the logic ICs do nothing.

[@simontay4851]

You wouldn't even need a microcontroller. He could use an off the shelf clock chip.

[@r7boatguy]

That calculator manual is fantastic!

[@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!...

[@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.

[@Enigma758]

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

[@2oqp577]

My older brother had one. When it was my turn to go to senior high, the use of slude rules was over.

[@Noneofyourbusiness2000]

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.

[@ericatkinson7006]

My SR 50 cost 150 USD, the summer of 1975.

[@oldguy9051]

If you were a baller engineer you wouldn't pay list price... ...and neither would your company if it provided it for you.

[@MrCarGuy]

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

[@Mr.Unacceptable]

Q5 Tranny looks like it got hot, not a retouch? U13 also looks like it got hot and shifted. Same solder ball. E12 also looks to have left skidmarks and shifted. R04 missing?

[@MattyEngland]

Was gonna suggest the same thing. Also next to that R12, is that just burnt flux on that via, or has the track itself got burnt? Hard to tell from the vid. Was it related to the incident that blew the fuse 🤔 Edit: looked at it on bigger screen, definitely just burnt flux

[@TeslaTales59]

When Bomar was introduced in the USA, it was advertised as the "The Bowmar Brain"

[@gregorymccoy6797]

Beat me to it.

[@reedreamer9518]

Wow hahah - when I was in high school if you were really smart the kids would mockingly call you a "Bowmar Brain", or just "Bowmar".

[@romancharak3675]

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.

[@MoisesCaster]

06:26 the resistor R12 is upside down.

[@bain19]

Looks burnt

[@evensgrey]

Simpsons was (having ended in 1991) a Canadian department store. Sears (a US department store chain) partnered with them to create Simsons-Sears, which later started trading under just the Sears name when they dropped a territorial restriction on proximity between stores under the two names. (By the time I'm old enough to recall, many malls had a Simpsons and a Sears. Simpsons was generally a lower cost store with lower grade store furnishings than Sears.) Simpsons ended up owned by The Bay (heard of The Hudson Bay Company? Same company.) and they ended the brand in 1991, converting it to The Bay stores. Sears Canada went bankrupt and was liquidated in 2017. (Sears had been a major retailer of home appliances, including having dedicate Sears-branded appliance stores, and carried the warranties in-house on their brands, leading to much consumer complaint when the warranties were very much up in the air.)

[@barrybogart5436]

The Bay bought Simpsons? Somehow I missed that. I remember The Bay buying Morgan's. Have you heard that Zellers is back? Kind of. It's Woodward's I really miss.

[@evensgrey]

@@barrybogart5436You might have missed The Bay buying Simsons because it happened a lot earlier than you might have suspected, all the way back in 1978, The Bay continued to operate the chain as Simpsons until 1991 (although the Montreal-area stores were closed or rebranded in 1989). If you miss Morgan's, you're clearly a good deal older than me. I was several months short of my second birthday when The Bay stopped operating that chain in 1972. And that was when they stopped using the name in Quebec, they rebranded the stores in Ontario to The Bay in 1964. More recently, I kind of miss Tractor Supply Company, now operating in Canada as Peavy Mart. The one in my area is exactly the same as it was before the name change. It's the only place I know of where I can buy fencing wire off the shelf. Damn fine stuff for making costume chainmail.

[@radman999]

"Simpsons Sears" was basically just "Sears", much like "Sears Roebuck" which was the US arm. Sears lasted until 2018 but was only really a huge department store player until the mid 90s or so. You could buy anything at these stores, appliances, clothing, electronics, beds, get your car fixed, insurance, watch repaired. They even sold DIY house kits by railcar in the early days. Was a huge catalog and retail business for decades.

[@barrybogart5436]

And Craftsman tools!

[@off-gridmountaineer4515]

On the 121GW Multimeter I seen what look like a burnt spot on the 4.000 Hurts Crystal. It was right near that chip. That was sideways that you was pointing out in the video. On the chipboard and on the crystal itself. I don't think it was the 4.000 Hertz crystal was burn. I think what was beside the crystal that is what burnt. It looks like it might have been a capacitor. That was burned out. But not really for sure. It was just a observe look at the chipboard on the multimeter But then again that could have been just flux and the factory didn't clean the board that good.

[@EEVblog]

It's a zero ohm resistor R12, and it measures fine.

[@bennyattar8862]

What about U9? something looks dodgy there

[@mikebarushok5361]

I still have my TI SR-52 that was a high school graduation present in 1975. It's the programmable version and had modules to add functions. If I remember correctly those were the only mass produced usage of bubble memory. In a university class on programmable calculators every one beside me had HP programmables and I was the only one able to get the final assignment done because of the register manipulation that the TI could do and writing self modifying code.

[@ymirthefrostgiant]

The SL800 is actually earlier - 1983; the SL760 is 1985. In a way it makes sense because model numbers often reflected the number of digits in the early days.

[@terrance_huang]

7:00 R12 looks unhappy

[@jfwfreo]

In high-school I had a Casio CFX-9850G graphics calculator and it helped me out a bit at uni as well in the math class I needed for my comp sci degree. Don't have it anymore unfortunately.

[@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??

[@TechBench]

If I recall, the battery pack contained three NiCd batteries, so the voltage would have been at least 3.6V, perhaps explaining why the displays are a bit dim at the 3V it was receiving during your test. Edit: on the SR-51, of course.

[@gretalaube91]

Meter repair: Just read comments: (I don't know, but I saw R12 had a black spot by it, and looked sketchy.) - posted before reading, good that everyone's got a keen eye, still! Also, I should wear my TI next time wife and I go out! Also love the discrete "darkroom" timer, too! RTL, anyone?

[@cidercreekranch]

Loved writing assembly on the PDP-11 and the VAX as well.

[@Enigma758]

Same here!

[@td4dotnet]

Awesome mailbag for us Calculator aficionados, I have a particular fetish for the credit card style myself and jealously covet my own examples. Love it! 😀Thanks Dave!

[@Richardincancale]

Special Barry Marshall chocolate with added Helicobacter Pyloris!

[@theelmonk]

Did TI ever do an SR-71 stealth calculator ? Bowmar were amongst the first calculator manufacturers. They sold displays and keyboards to others as well as making their own brand.

[@kevincozens6837]

Nice to see the old SR-51. I knew someone who had that back in the day. The other popular "fancy" calculator that was around when I was in Junior High School was the HP-67 with its built-in magnetic card reader.

[@SaltCollecta]

Bulging component at Q5 7:47 and scorch marks at R12 6:55

[@oldguy9051]

Yes, the "reflow" looks like amateur hour...

[@simontay4851]

Q5 is at 7:57, not 7:47

[@anthonyshiels9273]

I bought a Texas Instruments TI-59 after I started working. The display shown here is the same as the TI-59. You have to look at it from directly above. One day after the guarantee expired it broke down but as I ended up using it for work my employer funded the repairs. He did not buy it for me though.

[@barrybogart5436]

I had a 58. It was great. I got the celestial navigation card for it and sold it to a friend,

[@spacenomad5484]

The Scrabble Timer is a beauty. As handy-dandy as µC's are, I detest single-task processors. Good on ya!

[@bengineer_the]

I think it looks like it was a 'quick' piggyback repair - perhaps an open pin on the chip below & they felt it would be too hard to desolder? (I have often temporarily piggybacked ram chips onto old arcade boards (to help determine which one was glitching the screen), with the odd success.)

[@sotecluxan4221]

Got a casio fx-101, phps '72. In use, because of the big, green glowing display. Can be used in the dark without glasses! Fully functioning!

[@therealjammit]

Stacked chips: One chip would be an exact replica of the other except internally the chip enable would be active low. Edit: Do NOT operate the calculator with the AC adapter and no working NiCd battery pack. They use the batteries like a zener diode.

[@3v1Bunny]

the TI examples is awesome .. makes me scratch the back of the head again too.

[@mrwidget42]

I remember seeing these back in the day. Poly-Paks used to sell whole 100 ct bags of these single digit led's (man-3) for cheap-o bucks.

[@KeritechElectronics]

Awww yeah, an exceptional mailbag! I loved the TI calc and the business card ones - so thin! Pity that the prettiest one went come-a-gutser though.

[@joekenorer]

"Tight as a nuns nasty" I love you, Dave.

[@barrybogart5436]

Nice not-so-nasty version.

[@Robertkopp84]

Oh man I wanted to doze off while you slice up some packages and now I watched the whole thing again.

[@cambridgemart2075]

There appears to be a short between pins 20 and 21 on the DMM processor chip of the 121GW, there is definitely something there that shouldn't be

[@L4b3n]

121GW: spottet something around R12.

[@BaumInventions]

21:18 In the Speak n spell TI used very special roms. The roms have addresses hardcoded in. so you can just wire them completely parallel and address them in code. Maybe its the same here.

[@petersage5157]

Those Nobel Museum chocolates remind me of the chocolate coins he had back in the day. I've also seen commemorative chocolates like that for former Presidents. Forget the TI calculator - that Scrabble timer is going straight to the pool room. I don't play scrabble and I want one.

[@mikebarushok5361]

I had one of the generic film card calculators that went through the washing machine in a shirt pocket. If you held the layers aligned it worked fine.

[@bertblankenstein3738]

Scrabble timer, yep I'm in agreement on first reaction, I could do this on a TTGO board (esp32 w display), a few buttons and a buzzer/beeper/speakers. ESP32 aficionado here.

[@joegee2815]

My dad bought the SR-51 back in the 70s. It was not cheap. I learned trig from it.

[@PlasmaHH]

The old one from my grandfather was all the time counting....

[@flymypg]

Love the calculator fetish! My Casio fx-900 got me through my engineering degree in the early 80's. One day I had it in my back pocket and sat on it, giving it a distinct bend. It still worked, but I did get an fx-995 as a backup, just in case. Both still work today, of course, given they're Casio! But I don't use them, as these days I just pull up a calculator on my desktop or phone, or write a quick Python script. Sigh.

[@TheAussieRepairGuy]

I just sat down with a cuppa - this popped up, great timing

[@TheAussieRepairGuy]

Bloody scammers

[@KissAnalog]

Fun stuff! Love the Gw121

[@ESCcrasci]

When my mastech meter's fuse blew, it used to go into overflow and give erreneous readings. Not sure about the 121GW

[@victoriamarotosilva7093]

6:55 R12 seems to be a bit off.. 24:05 That's a setup for autodestruction.

[@cambridgemart2075]

I have a few of the Bowmar Optostic NOS in my parts box, I wonder if they sell for what that listing was priced at.

[@renreWydnaS]

I got the same calc and its perfectly possible to read the screen normally… so yours seems to be a bit strange 😅

[@redsquirrelftw]

To think that even in the early 2000's teachers told us we'd never have a calculator in our pocket!

[@Mr.Unacceptable]

Those digi-matic 8 display bulbs are cool as hell. I have use to repurpose those. Sure would like to find them somewhere. They would make amazing counters and displays for diorama's, models or DandD game room maps and models. Say an elevator counter. Anyone know how to find them?

[@yanfishtwig2356]

yes i was thinkiing along similer lines

[@mcconkeyb]

Nice calculator mailbag! I have several HP-IL accessories that were designed to work with the HP-41. I'd like to send them to you, but I'll have to win a lottery to afford the shipping 🙂

[@joopterwijn]

Is that dirt on pin 27/28 or so on the chip-set? Or a short…? ( @05:27 )

[@andye2005]

abt 6:50 in on the meter, R12 by the xtal looks to have had a hared time. Andy

[@Yaaayishere]

R12 looks dodgy as - right next to the crystal x2

[@IanScottJohnston]

Yep, spotted that.....touched up with a iron fire poker!

[@EEVblog]

Checked, that's ok. 0 ohms as it's supposed to be.

[@ventusprime]

9:00 other side?? , Probably the ADC chip or the amp before it. AMP feed back resistor???

[@leaveempty5320]

Must get a belt clip for my calculator......

[@graxxor]

That top black resistor is being very "Australian" @6:08....

[@bertblankenstein3738]

I'm a 6809 fan. My first computer was 6809 powered. Nice to see more recognition. Why should the Z80 and 6502 have all the fun?

[@barrybogart5436]

Was that a Coco or SuperPET, or sonething else? NICE processor. It would run OS-9, Unix clone. en.wikipedia.org/wiki/OS-9

[@bertblankenstein3738]

@@barrybogart5436 COCO2 Extended color basic. A whopping 16kB of RAM. I did basic and assembler on it in my teenage years.

[@riscy00]

I was wondering if you might do review between ARM cortex m0 versa risc-v. It would be interesting topic

[@matseriksson8177]

Once I used a voltmeter I didn't trust. I don't recall the exact value it read, but it was approximately 10^27 (1000000000000000000000000000) volts.

[@simontay4851]

6:09 why is that cluster of SMD resistors and caps unpopulated. What are they supposed to do?

[@simontay4851]

and U14.

[@valentinaselektrikas]

6:55 burned cap, short near crystal

[@PlasmaHH]

my 121gw doesnt really have a hard failure, its just for certain functionality I have to wiggle the knob a bit to make it recognize the right position... feels a bit cheap that way...

[@lesliefranklin1870]

Since Texas Instruments made their own chips, it's not so surprising they would be able to stack them. Sometimes when you run out of the X and Y board space, you are forced into the Z direction.

[@spedi6721]

Hi David. Are you still in contact with Andi from photonic induction? Is he well?

[@EEVblog]

Haven't contacted him for quite some time.

[@francoisbeaune3289]

At 6:31 resistor R12 is funky looking (burnt out?).

[@johncanty161]

hardoff is the Japanese version of best buy here in the states. I don't remember what the Australian version is.

[@martinkuliza]

Just realized something the BRYMEN 121GW IS THAT IN ANY WAY CONNECTED TO 1.21 GIGAWATTS Seems rather suspicious

[@jacques6753]

Multimeter: there seems to be something burnt near R12 close to the crystal next to the battery.

[@john.walker]

Heh, funny to see Hard Off mentioned here. It's a recycle shop with a really dumb name. Basically formed from Hardware and Off from "10% off" or Price off etc. Discount Hardware essentially. They do have all sorts of thing there though, cool places.

[@video99couk]

Wow I thought my Rockwell 1975 pocket calculator was old, never seen a 1972 model. I have a number of those display digits as used by the TI one, in my component drawer. Don't know where they came from.

[@worroSfOretsevraH]

Two hungarian Nobel prize winners last week.

[@TrickyNekro]

U17, seems also like a charge pump, would make sense.

[@Di3Leberwurst]

@3:55 Quite obvious what is wrong. It's stuck in reverse.

[@Manta_Dennis]

6:56 R12 looks bad too

[@hiredgun7186]

I saw what looks like a solder bridge on the MM chipset, left side, 2/3 way down, hard to tell though

[@atlekaland9404]

PDP-11 - That is from the 60ties or seventies? (early)?

[@barrybogart5436]

70s or later'. 60's was still second generation, discrete components and mag core memory.

[@jfwfreo]

Hardoff seems to be a 2nd hand store so the price stickers are probably not original.

[@gg-gn3re]

crazy the site is still up too lol. who knows what it was back then though, maybe they did make stuff

[@jfwfreo]

@@gg-gn3re Hardoff is still operating, they are a Japanese second hand store (kind of like a pawn shop but different). Hardoff probably bought the calculators from someone and then put the price stickers on there when they re-sold them.

[@10100rsn]

12:35 Takes 3 batteries, shouldn't that be 4.5v and not 3v like you had it set to?

[@brentdennard6722]

On the eevblog dmm, looks like a cap in the R12 position??

[@baxtardboy]

Looks like someone put the display prism in upside down.

[@MatthewSuffidy]

Maybe those two stacked chips have different part numbers and thus are re wired internally?

[@natedawww]

Mic used after the battery died in the other is better, less room echo!

[@jutukka]

Those calculators can be used as maracas. 🤔