Bumper mailbag!
Send stuff to:
EEVblog Mailbag
PO Box 7949
Norwest NSW 2153
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
Verilog: https://twitter.com/BrunoLevy01/status/1694973514002923808
Takachi Enclosures: https://www.takachi-enclosure.com/
If you find my videos useful you may consider supporting the EEVblog on Patreon: http://www.patreon.com/eevblog
Or with crypto:
BTC: 33BsprBQNBtHuVzVwDmqWkpDjYnCouwASM
ETH: 0x68114e40ff4dcdd384750500501e20acf3875f8c
BCH: 35n9KBPw9T7M3NGzpS3t4nUYEf9HbRmkm4
USDC: 0x68114e40ff4dcdd384750500501e20acf3875f8c
LTC: MJfK57ujxy55su4XicVGQc9wcEJf6mAoXF
Web Site: http://www.eevblog.com
Other channels:
EEVblog2: http://www.youtube.com/EEVblog2
EEVdiscover: https://www.youtube.com/eevdiscover
T-Shirts: http://teespring.com/stores/eevblog
#ElectronicsCreators #Mailbag #retro

Hi Welcome to everyone's favorite segment: Mailbag If you want to send something into the mail bag, if you're an individual or a company, send it to mailbags. Got to have mailbag on EV blog mailbag PO Box 7949 Norwest New South Wales 2153 Australia not Austria thank you very much. you'll know this name Barry Marshall Bazer Um has sent something in if you don't know I'll link in his video down below. he visited the lab.

it's not every day get something set in by a Nobel Prize winner Yes, he won a Nobel Prize in medicine and he's a vintage computer nerd and a vintage tech nerd as well. Anyway, um, this is kind of a sad oh um. he said I should open this on camera normally I wouldn't because it's um, he said there's something in here, but it is actually a return. A return of a faulty evlog meter.

It happens. um I've had a lot of Bman fires lately actually, but this is a 121. GW and he said, um, open this on camera and that's why cuz that is not the normal shipping box I Can assure you for a 121. GW So um, we have a note.

oh look what? I get look what? I I'm going to read the note first. this is so special. Um no, this is just our was our email. Um, it's no, that's it.

No no no, there's no explanation. but he said he would send something special. Look what? I got? look what? I got? It's a Nobell medal. Well it's not his one.

It's not his exact one cuz there's actually three of them. Yeah, um, but they are little noall. Med uh medals. Terrific.

Awesome. And look at this: I should actually have this package in for the 121 GW meter. Check that out. Sorry just realized the battery in my wireless mic on the camera um had failed.

So yeah, you're going to get really crappy. uh from Mike from on the camera which is meter and a halfway. Anyway, look at this box. I Should I should ship all my meters in in this sort of box? Check it out.

Isn't that groovy? Anyway, um yeah, he's got a failed 121. It's perfect. Look at it. A failed 121 GW meter.

Sad face? Um, yeah, it does. Actually, um, happen. fires aren't U they're not. You know, it's not a large number.

In fact. I get more bryman, uh fires than I do 121 Gws. although I haven't really correlated that with um, like it's beeping at me. it's beeping at me.

Yeah, it's something wrong that's just on Volts mode. Wow, haven't seen that one before anyway. um yeah. oh bumer.

I have to take a look at it and it turns out that these are actually chocolate. so I got don't want to eat them all. they're too good. but I've got to try one.

I've got to try a Nobel I wonder where he got them from? Didn't he get like a whole a a swag bag of him when he won his Nobel Prize I'm not sure but uh yeah, this looks like this looks like chocolate to me. Oh there we go. That is chocolate m I wonder I'm going to go for it m sorry nothing special about it. It's possible expect it a bit better from Nobel Priz chocolate.

So yeah I wonder where he got them from I wonder if you only get these? Um, if you like, attend the Nobel Prize ceremony or something? I don't know I'm I'm sure you can't just make these willy-nilly Anyway, thank you very much Bazer, let's have a look at the meter. Well yeah, something certainly come a gutter there. Um, never seen this fault before. Overflow as in like th000 Vol overflow.
Soes it? Do it on D No, it's okay on DC Okay on Millie A it's okay on AC Mill volts that's actually not updating. That's that's not updating that should be that should be changing. hello hello wow. Um, that's a strange one.

Got that on a voltage reference source. uh, three Vols and that's just that's just reading nothing but on M volts DC it's oh no no. I thought it was going to do something I've got 300 M feeding in 300 molts. If I feed in 3 volts, it overloads.

But if I feed in 300 molts, it just gives me .1 molts. That is weird. All right. let's have a look here and first thing I noticed is Baz has changed the fuse to a glass one.

None of that's Sur camic rubbish. That's all he had available. Obviously blew the fuse and well, we've all been there. Admittedly, these, um, this size and rating fuse is a little bit hard to get.

Yeah, let's let's have a look at the the visuals cuz this is a rather unusual, rather unusual fault. So there's the Hy 3131 chipset just looking looking and that's that's a nothing. Burger I'm not sure what that is that almost looks like. Oh, that's a bit of celastic because they do actually use celastic.

Um, over here to hold the crystal down over there. but um, yeah, we got our Bluetooth module and no, it's got the mod board on there I've done a video on that. um how to do mod boards? Uh so uh, the input I mean like if if any of the input was broken like you know input, uh, the input resistors or anything. um then of course you wouldn't get anything you wouldn't read overload.

It's uh yeah, why would you be reading overload? That's had a bit of a touchup there. Not sure what's doing there. that was not Bazer I'm sure. And yes Barry no one calls Barry Barry in Australia it's Bazer.

It's how it works here in Australia Well, that's interesting. that one has come. Guts are sideways. not sure what's doing there off hand I don't remember what that part is, but yeah, that's um, that does that.

Looks to have been hand done at the factory for some reason and they goofed it cuz that's not. you know. Look, look nice. you know, Nice.

Beautiful. Reflow Over here, right? Beautiful. Beautiful. and that's been sort of.

I Don't know what's going on there, but uh, in fact I've got to get in there at an angle. It's hard to get the Tano on an angle here cuz I have to drop it I have to raise it up higher to get the focus range, but that actually looks okay there. There's nothing actually wrong there. It is actually connected and it's not shorted.
so I don't think that's an issue. not really seeing anything. Visual: The multimeter chipet is where all the magic happens cuz it's not going to be the processor doing it right. The processor is going to which is on the um, other side of the board.

It's going to get the you know the info from the chipset that tells it it's overrange and then the meter just does what it does and uh, yeah, it. it indicates an overload. So something strange is indeed going on here. Um, this is quite an old unit.

Yeah, this is quite an old unit. Dates from uh, 2018, so it's uh, it's had a decent life. But I don't know. Yeah, no, no there nothing.

nothing visual. So yeah, um, the mod board doesn't exist anymore of course. Yeah, so this would have been an early batch. There's something more subtle going on in here and that is not the time for the mailbag, unfortunately.

So um, yeah. I'm going to have to leave that to a second video. but I'll send Bazer a new meter. This one will have to be a work in progress.

I'm afraid, but leave it in the comments down below if you've spotted something. but I doubt it's It's almost certainly electrical I would guess, but I don't know. Um, it's yeah. I mean Fa is pretty rare in it, but yeah.

and I've never seen one like this before that causes an overload. That's just I don't know. It's like maxing out the ADC and it's thinking that it's overload. Warning: Will Robinson that's why it was beeping.

That was the warning. You know the high voltage warning beep. Um, don't know. Sorry Bazer, that sucks.

I'll send you a newe next up. Hi to all my viewers in Canada in particular. Montreal and uh, this one comes from an H Cus whove we've I'm sure this is at least the second Su suck of the mailbag. So we do like what's in here.

It's one of the, uh, perennial favorite items on the EV blog mail bag. So yes, never cut to towards yourself I am a professional I am using the correct tongue angle didn't quite get through that one evenly. Maybe I have to sharpen the knife? Oh oo whoa, look at this. Look at this.

Wow! We got two Ti calculators complete with their original owners well, owner, manual and operating guys. All the Ti Fanboys go wild you know I'm a C man myself. sorry for all you TI Fanboys But look at that. oh oh that one's is that I've got an Sr51 which rattles doesn't sound that good.

Let's have a look. this is not the original pouch. this is an original TI pouch though. jeez, that's in good.

Nick Wow wow that's in Fant Got even the belt clip carried around your belt. He leave it in the comments down below if you carried it around in your belt. oh my goodness, look at this. I Don't think we've ever had a made in Canada calculator before.

It's a digimatic 8. Look at this. it's a four banger and it like take a closer look at this but wow it is like again that doesn't sound good. Uh let's go go to the bench, check out this.
Bobby Doler. We're talking 1974 75ish vintage. We'll find out when we, uh, tear it apart. but uh yeah, this is the original Sr 51.

It actually was, uh, very quickly replaced apparently with the 51 A. So this was only out for a couple of months. Uh, one report, uh goes anyway. and then they released an Sr51 uh Mark 2 or -2 or or something like that.

So yeah, this is one of the originals and it's a super slide rule calculator. Look at that back when you know people were still thinking I like my slide rule but these new fangle calculators oh, this one's an it's an electronic super slide rule Fantastic! I'll have a go with that and uh, 2,892 serial number there and was that actually manufactured in Dallas Texas I I assume so I don't know, leave it in the comments down below if you know. but uh. anyway, they've got some uh conversions there.

There you go Mills to microns like and you can actually put in the code. so wow, that's actually built in. That's quite something. and it's got some uh, statistical uh stuff as well.

So this is more advanced than your regular um, scientific calculator lead uh, red bubble display of course I believe it's a 10 digigit plus 2digit exponent. Nice. All sorts of stuff. This would have been pretty hot stuff back in the day and if we get the battery compartment out, we will see uhoh um the contacts of battery contacts of uh Kamaga and well, that looks like why it's oh, anything else in there and all.

this is uh, why it was rattling around. so yeah, but uh, it's been marked negative positive there but you can tell by the there somebody's marked it red at the factory there. so um yeah, we can just hook into there no worries. uh and looks like we had a card Edge connector that's not for expansion or anything like that I believe that would just be for uh, production testing.

So yeah, oh, there you go. We got a DI in there and um, yeah, that's it. So it's just got a diode in there for the external uh plug pack if you you know cuz these things drew a bit of power so you know you might want to. uh and batteries were expensive back then I guess.

All right so let's power this up 3 volts and uh, see what we get shall We There You Go Uh, 40 46 milliamps, it's working. Oh jeez, hang on. I'm going to have to turn the studio lights off here. That's a bit low, but it's there.

Oh, it's there. Yeah, there it is. there. It is.

It works. Of course it works. I would totally expect this to work. Three, 4, 5, 6, 7, 8, nine, 10 digigit and a twod digigit exponent.

There you go. Look at that. What a Bobby desler. That screen is really weird.

Like if I'm using it like flat on the desk like that I can't actually read that I've got to tilt that up I've got to tilt it right up in an angle like that. so I'm not sure what the deal was. That can't be how it was back in the day. Leave it in the comments down below that that just can't be it.
I mean that's like beyond straight down. it's actually like yeah, I don't I don't understand what's going on there. Somebody hacked around with the Optics in there or something, but that doesn't seem to make sense. like I can't even read that.

there's a giant strip across there and it's not really um to do with like the reflection of the lights overhead or anything. So anyway, does work. anyway. we can do the calculator forensic 9 sin cos tan and then invert tan, invert cos and invert s Oh no, that's hyperbolic up.

That's not inverse. It's hyperbolic. Can we do what? can't do inverse? Um, that kind of sucks. It's got a random number generator.

Two digigit random number generator could have done better than that. Check out the operating guide here. Little um, you know, a ring binder. It's not the uh owner's manual.

That's uh, separate. But yeah, this is just like a quick reference uh, guide kind of thing. Uh, mathematical hierarchy. You need to know that for your calculator trig functions.

There you go. We can do um, inverse sign. So is that the second no in inverse. Is there an where's the where's the inverse? Oh, there's the inverse button.

Okay, right. I get it now so we can do that. Now we can go 9 s cos tan and then Arc tan Arc cos arc S Uh, we're not. We, we're not.

Oh, is that a nine? No, that's a four dumb ass. Me: I was in radians mode. Stick it over to degrees mode there Dave um right nine s cosine Tangent: There you go I should have known that Well, I did I realized give me a break? There you go. 9.00 4661 and if you go, look up the data forensics for that that will match the Ti chipset used in this bad boy.

But yeah I Got to tell you that screen is awful like I can't use that I can't use it unless I like get like a couple of like degrees like 5 Dee window there of of tilt on that. That's not just the camera, that's not just Reflections or anything. that's just like what. Maybe somebody's maybe the else.

somebody's had a hack at this and the screen's moved or something. Maybe then we have the actual owner manual here and I just flipped through a random page and I found this. This is absolutely hilarious. Check it out.

Um, like in like they've got examples like aerodynamics. You know an airplane is a steady coordinated turn true a speed 50 Bank angle. What is the turn radius in feet and all that sort of stuff and they help you figure that out. This one's hilarious.

Over here. look at this meter correction: An electrical engineer wishes to measure the signal level of a voice Channel You do that all the time having an equivalent pedance of 150. Ohms the power measuring test set. Everyone's got one of those that he can provide termination resistance of either 600 ohms or 150 ohms.
but the deflecting meter n that digital rubbish is only calibrated for 600 ohms. What correction factor should apply to the meteres where the channel is terminated in 150 ohms? Try that question in a modern Electronics exam and see how far you get. That's great and you guess that the answer is 6.02 DB Before he uses the calculator, he recalls that the voltage ratio to Decb conversion provided with the calculator is defined as 20 log. Thus, he must divide this result by two to obtain the answer he needs.

This is great Cam Problem: Torque problem: Look: distributed transmission line parameters Wow. Characteristic Impedance: Wow. this is great. Like this is a vector Edition This is great stuff.

Approximation: Monte Car Method: Wow. Approximating integrals and stuff like that like solution to differential equations, approximating derivatives, algebraic equations. Wow. this is really try really register level processing.

Oh there you go. So like the equivalent to like assembler for a calculator Really? Um, yeah. like you can keep it in in the registers and the memory and you can, you know, do a bit more advanced stuff with fewer key presses. Linear Regression I Inverse Function Wow.

is this all like Examples: I Literally haven't even looked at the front table of contents yet. There's the key. uh. Index: Physical Science: look Statistical applications, Engineering, Mathematics, Business and Finance Wow.

Sum of products Product of sums. Your Sr51 is a powerful computational tool capable of solving a wide variety of problems. It has been designed for those who require an accurate, relable, and versatile slide rule calculator. because your Sr51 uses the algebraic mode.

None of that. RPM Rubbish. You can probably already perform most calculations, However, to assist you obtaining the most benefit, we have prepared this owner manual and guide this is this is great stuff. I This is absolutely fantastic I Love this and it's almost like a bol one too.

Wow that Pages haven't really yellowed or anything that's in one onee warranty. Send it back to the Ti printed in the United States of America USA This bad boy has metal threat Ed Inserts thank you very much. Three screws there and we pop it right off. That's surface mount rubbish.

Look at this. Oh, hang on. it's upside down. All the electrons are going to fall out.

Don't want that? It's the worst thing that can happen to your calculator. and uh, we've got yeah. 75 10th week? Uh 75 Yeah, Fifth week 75. There you go.

Apparently there are some of these 74 uh vintage. but as I said, this didn't last long. They released an A version. so I'm not sure what difference uh, the a version uh makes.

but anyway, there's a little dood just in series with the input there. So um, you know you can't get the polarity wrong, but uh. anyway, it's just a four chip solution and 74 LS uh, is that 240 there and what? The other one and a 74 Ls02? That's it. So a couple of uh, Ttls and you know the low power shocky.
This thing only draws 50 milliamps. It's you know. sniffer for an oily rag stu Oh, this is piggybacked. Look, it's piggybacked.

piggyback chipped. Wow. look at that. Why have they done that? Why have they? There's no, they're they're solded all in parallel.

Wow, uh, how does that work? It's like you usually like. you know back in back in the day when I was a boy, you would make a ram stack um, as it was called or a ROM stack. Um, and you could actually stack the memory chips cuz all the address and data lines all in parallel and all you had to break out. You know, power address data.

They're all in parallel. so you sold to the TP chips one on top of the other. Usually you put like a socket in there so that you could actually take them. AP and then you actually just bring out one of the bring out the uh chip select uh pin.

There's no such thing happening there is there. I'm not I'm not seeing it. If anyone knows why, they actually stack two chips physically in parallel. Is it a dry thing? Drive Capability thing.

That's interesting. Anyway, there you go. Um, that's a fascinating look at this. Uh TI 51 Slide Sr51 Slide Rule calculator and well, it's a Bobby dazzler apart from the screen screen.

Um which I never figured out did I Okay, we have five screws and don't want all the keys to fall out. but there you go. So oh no, there's the there's the L ah yeah, look look, it's been cracked. yeah I think that's yeah.

I think that's moved I think that's moved. Actually better off taking that out. Actually, there you go. Yeah, look, it's cracked there.

So I reckon that's what's happened. It's cracked and then it's uh, tilted at the wrong angle and just can't uh see it. But there you go. There's the little tactile domes still work after all this time.

and God old plated tracers. We've got two extra chips on the bottom. actually two sneaky little uh, 74 series chips. They are actually uh, 51st Week 1974 So oh there you go.

Bit of reflection off the keys there overexposes the camera there. but uh yeah. look and these use individual bubble displays. Unlike like the HP jobbies were all integrated, these ones are actually individual like that.

Wow. I don't think I've seen those before with that staggered pin Arrangement Isn't that terrific? Yeah, HP did that did that somewhat differently. but I guess that's how I did TI make these leads I'm not actually sure I should know that. Then you've got just all the individual.

Loosey Goosey Keys Like that that' be a dog at production time, wouldn't it? Jeez. And then the switches in there. they just got like sliding contacts like that on onto the gold plated traces. Nice.
All right. let's try and power this up. Who? look at that? Oh look, oh why is that counting? What? What? Uh, what? am I what was I doing was I accidentally doing couple of traces. How the heck did I get that? Anyway, there you go.

Um yeah, these are not very good lead displays. Oh, they're so we. What? What the heck? How did I get that count? That's hilarious I have no clue how I got that to count up. If anyone knows, leave it in the comments down below.

Maybe I'll get a clue when I watch this video back during the edit but I don't know was I I must have been touching something shorting out to some I like I no I don't get it just for you. charge a plug pack of fishy and AO look at that genuine Texas Instruments US patent pending made in the United States of America and yeah, 6V AC So 175 milliamps. it was actually 5 wats it was actually yeah. so you put rechargeable batteries in this thing cuz as you saw it, drew 50 milliamps.

So what the heck is this thing? The digimatic 8. It's a 4 Banger um as they're called in the trade. Um and oh that's a oh that's a stiff as operation outline refer to instruction manual for complete details since it's like how to use a for Banger Thank you very much. Um, and in all correspondence regarding this article, always mentioned model number 41030 What the heck is this? Um Ser they made 1,000 of these made in Canada expressly for Simpsons Sears and Simpsons is that like a A department? Sounds like a department store or something like that.

Uh, leave it in the comments down below. Hands up. if you had one of these. oh, look at that.

that's for the uh plug pack which I do have with it. Oh goodness like wow. What? Oh, you can only use it with the plug pack. There's no batteries at all.

Seriously? okay. I'm going to give it a B. Um, got one of those Yankee adapters and uh, we'll maybe it has a rechargeable battery in it. Well it turns out I can't because my 120 volt um like Transformer is missing in action I don't know where it is got my isolation Transformer but oh I things just disappear in the lab.

It's unbelievable. Stuff gets moved around all the time. Oh sorry, let's just take it apart. All right.

let's get it. Oh yeah, look there's the battery. oh hey hey hello. that wouldn't have worked anyway.

What? No, no that's in. that's in parallel. it might have go. Oh look oh what's that that's got a bit? Ernie Burnie there.

Look at that. Um yeah. like it plugs into there. anyway.

Two Ball Construction PM 905 plus 7.2 Vols and the batter is just like Loosey Goosey it's just flapping around. Oh, it's just flapping around in the breeze. There, it's a GP silver charge 280k. Oh, it's a Radio Shack Jobby made in Hong Kong resealable safety vent.

Yeah, after a vent, you want to reseal it. Wow, look at that. It's a TI chipset. Um, look 1972 So it's an early, uh, one of the early TI chipsets.
None of that piggyback stuff this time. Um yeah. Anyway, we got a board to board interconnect there and looks like that's nine digits is it? And of course there's no exponent. There's no none of that scientific rubbish.

bow leave it in the comments if you've ever heard of Bomar Uh, Op Totic Optic. is that what that's B bowar um I I don't know. Is it a bowar display? Is that I've never heard of BMA Anyway, look, that's an interesting, uh flat Arrangement like nine Digigit Jobby and she's a bit, uh, bit. Rusty Yeah, this is a bit crusty.

Um, don't like it at all I You know? Yeah, yeah. Anyway, that looks like it's um, three, uh 1.2 Vol Nikad. So yeah, let me run a 3.6 onto here and uh, see what we get? Well we're getting 70 milliamp drawer there. so it's doing it's.

doing something carefully. Flip it over. Oh yeah, look at that winner winner chicken dinner. That's that's better than the Ti one so look still works.

No worries. No the six but oh no. six is a bit sticky Oh e e oh okay, no. so it's only eight digit.

Oh yeah, that is very limited is it not? But you know would have been useful back in the day. How much did this cost? Um, like leave it in the comments. did you ever have one back in What? 72 was it? Wow, that's really going back. One of the early TI Four Banger chipsets Anyway, thank you very much and for sending those in the Ti Sr 51 is going straight to the pool room I Don't know about this one though, but you know it's got it place.

Maybe there's a whole bunch of fan booys out there who are enraged. Next up, hi to all my viewers in Japan Thank you very much Keith SE for sending this in to follow on from the previous one. Let's have a squares at what we got here. this I it it the description does not fit the form factor if you know what I mean.

So let's have a look what's in here I'm going to note: oh look, check it out. We got classic 1980s folding calculator wallets. Oh wow oh there's a whole bunch of look. Oh Casio SL 760 Haven't I done a tear down I think I've done a tear down of that haven't I I I'm pretty.

It was one of the Casio Oh wow. a whole bunch of them. SEO This is a bananza. A bonanza of credit card calculators.

Casio um SL 760 in a different ver Oh, that one still works at that solar jobby still works. Of course it still works. It's a Casio wow. this is and they got the original pouches at Sl73 Casio SL 760's Aeno and whatever.

This is a gent. I don't know. it's very sophisticated, but we're not done yet. What is in here? This is the oh hey, there you go.

It's not a calculator. learn multiplatform assembly program in there you go. We've got a book. it looks like Keith did write it.

Awesome! so we'll take a quick squiz at that. And we got calculators. Fantastic! Ah, Keith actually sent in a book before, so this is another book that is written and apparently after it was featured on the mailbag, it was quite popular and sold quite well. This is a number.
This is an Amazon uh, Kindle KDP or uh, you know, print on demand and it's it's a hard cover print on demand. This looks great quality for Kindle I Don't think I've ever seen a Kindle print on demand hard cover before that's actually really quite good. And uh, and to answer the question that I had last time, did he actually draw all of the um stuff in the books himself and he said yes. So presumably this one is, well, awesome and he's planning a third book next year with another five assembly languages, so we may hear from Keith again.

Wow, If you're in, what does this one cover? Multiplatform Assembly program? How do you do multiplatform assembly programming? I Guess we have to read the book to find out. So this is Keith's book anyway. Um, Assembly Tutorial.com Um, and it's also learn Asm.com KDP system and they print on demand basically. um.

so the oh, it's got got a YouTube uh Channel as well for video. uh, tutorials. completely created, entirely free and open source software. So he wants to promote the fact that anyone can actually, uh, like, do like publish their own book.

And yes, I would recommend it. Um, it. and look, he's drawing his own stuff. So technical terminology of assembly and retro programming.

So anyway, I won't won't spoil it too much. dis images and tape images, signed numbers, how they work, words, octal, all that sort of stuff. You got your Asis It's got graphics, uh, terminology. digital how digital and analog joysticks work.

Very like I Love the diagrams. they're great defining bites of data in on the arm in V ASM Um, so this is all like Assembly Language stuff and it's multiple languages. so you've got the Uh so it's basically generic stuff. Then you got arm thumb.

then you got 65816. Uh, then you got the classic 6809 and what the PDP 11 and then uh, then modern stuff. You've got the Risk five. Absolutely fantastic.

Let's go to Risk Five, shall we? So there it is. The Risk Five, which uh, we talked about a lot on the amp. um and yeah, the the Stack and Risk five. Assembly Language And like this is like really amazing in fact I we talked about on the amp and I did tweet it or retweeted it or something.

Um, where somebody wrote an entire risk Five core in like like 50 lines or something of uh, verilog or something like that. It was absolutely like Bare Bones or something. It was absolutely, um, crazy. So there you go.

That could be good if you want to get into your Risk Five stuff. So anyway, so great work! Keith That's absolutely fantastic multiplatform assembly programming with the uh Chibi Aamus is an introduction I Guess he writes that looks like it's an application or something and he writes it in different languages I assume that's what it is chi Akuma are the characters I created for the 8bit Amstrad CPC game I wrote in in Z8 assembler after I wrote the game I started creating YouTube videos covering assembly uh, content using gamer subject material. Yeah, so it looks like he's like porting that like to different platforms and using that as a uh, learning thing. So yeah, that's absolutely terrific.
So great work Keith I'll link in Keith books down below. Terrific stuff. Love people like So easy to self-publish these days. And they print on demand so there's no wastage so you order one book.

Amazon will print it even hard cover like this. They'll print it and buy it. They've got the uh, magical machines that do that and um, yeah, Bob's your uncle and check them out retro Cals and look, three of them are working. Oh, that one's just just working.

but these are working absolutely fine. Solar powered? No. Walkers right there. They're only four bangers.

Although you know you can argue it's more because it's got the square roots in it. But yeah, these were a thing back in the 80s. These are all SL 760 and you could like get them branded on your own company name film card. and I've done a tear down.

uh in one of my oh there you go. original price tag hard off code. do hard off. Great website code.

Jaapan, you get more than calculators there I'm sure. Anyway, these are made in Japan all the best stuff's made in Japan and um, yeah, credit card film size calculators now. I'll link in a video I've done a tear down of one of these which I think is the world's slimmest one. These ones look thicker than the one I tore down but don't quote me on that and this SEO one is even thicker again so SEO couldn't quite match Casio but this one does.

uh, data memo and stuff so you know it's almost like one of those you know 1980s uh digital diary, uh type things I guess. Turns out the one I tore down was the Sl800. so I presume that this one the SL 760 predates that H So yeah, I do believe these are thicker. Uh, this is 2.85 mm and by looking at my video, didn't watch the whole thing.

Uh to see if I actually measured that. but yeah it it was thinner than this. So the Sl800 I've torn down is a newer generation of this SL 760. But there you go, aren't they? Cute little, you know you can keep them in your wallet back then and you had a calculator ready if you didn't of course have a calculator watch which everyone did in the it was the 1980s man and just the top it off.

Oh imagine if you flip this out in the 1980s. oh it's the Gent Oh look at the like the simulated um like marble finish on that and once again that works. An absolute treat. No worries at all.

like yep we can clear that that's great and he's absolutely terrific. Even comes with square root. but look at the Gent Hands up if you had the Gent LC 517. oh that's just pure pure wankery.
I See screws I'm going to open that cuz these things you can't. They got no screws on them, You can't open them, they're all uh glued together. But this one all right. Let's go.

Oh look at that. that's far too easy. There you go. just a really Slim like that's not even 8 mm board.

like .5 mm or something like that. There'll just be a chip on board on the other side and I won't even bother taking that out. will I No, it's not chip on board. There you go.

look at that. Oh oh my LCD fell out. Don't you hate it when your LCD falls out out? damn it. But yeah, hopefully you can see in there that is not a chip on board.

that's just a a slim, um flat pack. Then the LCD I'm not sure if that uh, was that just a press. Is that just a press fit holding that on? no no. I think I've I think it's coma I'll try and put that back together.

but anyway, um, thank you very much Keith for sending in the book and these uh, classic little film card calculators I could try and take one of these ones apart and uh, compare it with the Sl800 so that might be interesting to see cuz I'm sure this was before cuz it's uh, well, it's got a number that's lower and it's um, thicker. so I presume they hadn't perfected that really Slim technology they did in the SL 800. H Anyway, leave in comments down below if you want me to do a video dedicated to like demolding delaminating this like I did with The Sl800. Next up, we got one from Hungary So hi to all my viewers in Hungary in particular Budapest and Daniel naggie.

Thank you very much I'm sorry this one's been here for a while I just picked them randomly From the Bench I should do them in or in the order that I actually get them I'm hopeless at this Anyway, the note is on top so I can uh read it I've been a follower your channel for several years recently and appreciate content. Thank you very much. Enter, educational and entertaining. Finally, I would do the pleasure of su win! The homemade project is a simple countdown timer that I made for my family to use when playing games such as Scrabble or I I Don't think we've ever played Scrabble with a time limit before, so that's interesting.

Um, right. So we've got oh, it feels like a like an actual it's not just a bare board. it feels like a complete product. Let's have a look.

oh wow. look that that looks pretty professional doesn't it? Scrabble timer. Look at that I like that. that's Jazzy Wow on and what on and I got to push the power.

Where is the battery dead? It's been sitting on the shelf for so long the battery could be dead. Ah no, he included a battery. All right. And we got some postcards.

Apparently we like postcards. People do like. the people do like to see postcards. so there.

Go buest. Very nice. Never been there, but that looks lovely. There's another one most excellent.

and this is the and this is the Prototype Look at that. that's fantastic. We got a the Prototype of this project and that turns out to be a nice that that's a nice build. I Really like that and looks like he's used a case with like an off-the-shelf case with two AA battery holders.
You can get those. There's lots of infinite variations of off the-shelf cases that use battery holders, so you don't have to design your own integrated, uh, battery holder at all. So yeah, um, so you choose a case and then you design your product around the off-the-shelf case that you get. and that's quite common, even in volume.

Um, you can. you know they're still reasonably, uh, affordable? I That just looks really cool. So check out Daniel's Scrabble timer. doesn't that look neat? That's contact, Trust me.

I've used a lot of contact to make front panels um, back in the day so he's like laser printed that and then just put contact on the uh top? Um yeah my. Pro Some of my projects published in the electronics magazines had contact paper printed and then contact UM front covers. So yeah. anyway, um so this just uses and Off the Shelf looks like it three times.

Is that like three times speed I Don't know, Is that a thing? I don't I don't know. Scrabble had a time limit Anyway, um yeah as I said these cases, uh, you buy off the shelf. oh look, long life V made in Germany none that alkaline rubbish. these aren't going to leak.

so Bobby doler so let's put that on there. Yeah as I said, you can get these off the shelf cases. not sure who uh makes this particular one, but oh look there you go. So start.

It's got a little backlight there just in the dark, you're playing Scrabble in the dark and um it. it just counts down. like that would have been nice I guess if it had like bigger like buttons so that you didn't have to like like fiddle with the uh, little ones you know. Small criticism there.

I'm sure it beeps. um at the end of this and we could have set the time there. So yep, oh it goes up in 10c increments. Yeah, you don't want one second rubbish.

that's just around. Yeah, he don't want 10 minutes per turn. so 20 seconds there you go and light comes on at the same time. Yep, and we'll wait for that.

it's going to go beepy beep beep beep and that's neat I Just like that it's like specifically yeah, okay, you can just get a timer from anywhere right? But it's not a Scrabble timer right? And it's not like Purpose Design like that. I Like that he's got like an off the shelf. he's found an offthe shelf. or is that did he use only one of the digit? Is that actually? Cuz usually you'd get the LCD longer.

Let's open it up and see if he's actually just windowed off um, any extra digits in there cuz normally I think you might be hard pressed to get um, that three digigit with the uh time um, thing in there. So anyway, yeah, it did be. Let's open it up oh tight as a Nuns nasty and let's crack it open and isn't that? And yeah, I was right I was right I called it. There you go.
a bigger LCD there anyway. Version 1.0 didn't that to respin that? Oh no. Rev C Timer 1.0 rev board rev uh C look at that isn't that neat. So there's just a whole bunch of um wise, like oh, there's a lot in here for a timer.

There's an awful lot in here. There you go. look at. this is just beautiful.

Look at this right bottom, big clunk and switch on the bottom. We got our power supply down there. not quite sure where you'd need to go to that effort on the uh Power side of things, but look at this double-sided load. I'm going to have to get like I can't see this.

You can probably see it on your new fangled HD screens I can't see it on my little ply camcorder screen I Got HC 192s and 45 43s and just a whole bunch of Um caps and resistors and what do we got on the top here? There we go. I'll let you have a look at those assuming you can get the numbers at the right angle and um, is this all discreet logic? What is this bad boy down here? 74 HC 574 Yep This is all discreet logic. That's the only thing that made sense. Okay, huge hats off for going all discreet Logic on that.

Very very nice I Like it I Really like it, hence the complexity. Of course you could just do this with a single micro just running uh from the Uh coin Sals But where's the challenge in that? I Like that. Wow, that is terrific. There you go I Assume that this is open.

There you go. It's it's beautiful. Oops beeping That is great. That is all discreet logic.

Um, he didn't actually say that in here, but that is terrific and it doesn't look like Daniel's um, selling it. but uh, there's his email. If you want to, uh, contact him, Maybe he might, uh, share the uh, schematics and open source this thing cuz I' I'd be proud of that. like if I did did like discreet logic like that.

Nobody does that anymore and it's a shame because it's It's just great I love it. and I love the uh, just just the windowing off of the front of the Uh case there. So ah yes, it's a H Tekashi case. Yeah, they've got.

uh, they make a ton of different, um, variety cases. So oh, there you go. Oh, and he's put. like, rather than have your traditional ones that mount onto the there and have the shaft coming out, he's actually done these as little things and just individually taped down little buttons on there.

a he's gone to quite significant effort there. Anyway, Hats off! I Like that. that's the wind. The Eev Blog Design of the Week award Anyway, hope you enjoyed mailbag and if you did, please give it a big thumbs up.

And as always, discuss down below, catch you next time.

Avatar photo


21 thoughts on “Eevblog 1571 – nobel prize winning mailbag. 121gw, retro calcs, assembly, and discrete logic”
  1. Avataaar/Circle Created with python_avatars KuusamoMart says:

    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.

  2. Avataaar/Circle Created with python_avatars KuusamoMart says:

    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

  3. Avataaar/Circle Created with python_avatars Hola! The collapse Of the west says:

    Ever since Obama was given a Nobel prize for dividing a country, it has completely lost all prestige and means absolutely nothing.

  4. Avataaar/Circle Created with python_avatars Ymir the Frost Giant says:

    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.

  5. Avataaar/Circle Created with python_avatars Ymir the Frost Giant says:

    $148.95 new in 72.

  6. Avataaar/Circle Created with python_avatars Ymir the Frost Giant says:

    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.

  7. Avataaar/Circle Created with python_avatars Mats Eriksson says:

    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.

  8. Avataaar/Circle Created with python_avatars John Walker says:

    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.

  9. Avataaar/Circle Created with python_avatars John Canty says:

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

  10. Avataaar/Circle Created with python_avatars Richard Payne says:

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

  11. Avataaar/Circle Created with python_avatars TechBench says:

    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.

  12. Avataaar/Circle Created with python_avatars Space Nomad says:

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

  13. Avataaar/Circle Created with python_avatars Roman Charak says:

    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.

  14. Avataaar/Circle Created with python_avatars Red Squirrel says:

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

  15. Avataaar/Circle Created with python_avatars Jammit Timmaj says:

    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.

  16. Avataaar/Circle Created with python_avatars RockyMountainFacet says:


  17. Avataaar/Circle Created with python_avatars JouMxyzptlk says:

    What is the page which does have that sin/cos/tan/reverse test list? I got 9.000279…. But google fails today to find the right site!

  18. Avataaar/Circle Created with python_avatars Dave Turner says:

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

  19. Avataaar/Circle Created with python_avatars Brian McConkey says:

    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 🙂

  20. Avataaar/Circle Created with python_avatars Angi Harrover says:

    Look at R12

  21. Avataaar/Circle Created with python_avatars Sam Jones says:

    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.

Leave a Reply

Your email address will not be published. Required fields are marked *