Hi welcome to Tear down Tuesday Quick announcement before we get into it. Uh, for those who have been asking, where can they get one of these warranty void if not removed t-shirts Well, you obviously missed my previous uh Teespring crowdfunding campaign for it. So I've started again. For those who have asked, the link is down below.

If you want one, they're pretty cheap. They're only 15 bucks and pretty cheap postage within the US Other countries are a bit more expensive, but hey, it's not bad at all. Certainly cheaper than my Zazzle store originally was. so if you want to NAB one.

the campaign only runs for a short time so link is down below. go and that one if you want it. They're available in women's uh Styles and hoodies and winter jumpers and all sorts of things. So excellent.

Warranty void if not removed I Love it! Anyway, we're going to take a look at this Tektronix. Oh, look at this. This Tektronics213 handheld, um, not quite a pocket oscilloscope. He had a really big pocket you could call it a pocket oscilloscope, but vintage handheld portable scope from 1975.

haha. Fantastic vintage technology. Had this hanging around for a while, got in the mailbag so let's check it out. and here it is.

Isn't it just gorgeous? Look at this state-of-the-art technology in 1975 and not only is it an oscilloscope as you'd expect, um, it's a one megahertz oscilloscope, by the way. One megahertz bandwidth. Look at that nice crisp trace on that. Oh, it's just beautiful.

Um, but yeah, not not a huge bandwidth, but good enough for a portable scope, especially for 1975. But it's also a multimeter as well. and a pretty decent multimeter at that. It's a three and a half digit, but it's 0.1 percent.

uh, plus one counter a meter. It does um, milliamps and ohms and uh also uh, true RMS AC as well. So pretty impressive stuff. Look at that.

generating the characters with the CRT. There's a specific Uh custom CRT character generator chip inside this thing which we'll see. And yes, we do have the full schematics for this baby. But oh, look at this.

Isn't it? Just a thing of beauty, really. And these are the input uh controls here. Here's your multimeter. uh import Jacks They didn't use the B and C The Bnc's on the back, by the way.

There's nothing else there on the back, but we can change the intensity and we can change the calibration of the horizontal and the vertical as well. And we can change the Uh trigger and it's got auto trigger mode and Uh AC DC input coupling. No, it is not an isolated Um scope, but hey, you know, for a portable scope. Oh, fantastic.

I Don't think anything else ever matched this thing really. And to have a CRT inside that that is terrific I mean granted it is a really small screen, but hey, very useful back in this day. I'm sure 1975. Not sure exactly when this one was manufactured.

We'll find out when we open it up and take a look at the day code. So let's go. So a big thanks to Derek White, who, uh, sent this in to the mailbag some time ago. sorry.

it's taken me a while to get around to it. Look at that. That's really quite nice. I think there's only four screws on the bottom here.

there's two on the front which hold this. uh, you know. yeah, there we go. can't get that one out.

But anyway, and there's looks like there's two on the back here. and uh, 1975? Well, it's all going to be. It's all going to be dip uh, componentry. that's for sure.

dip I see is the custom character generator ROM There's some 4000 series CMOS And yes, we do have the full schematics which I'll show you later and which I'll link in down below and there's actually a Wiki uh page on the tech Wiki Looks like the lid does come off here. hey Hello whoa, hey well hell look at that and there's a bit of uh, 40 year old crustiness I Mean you've got to remember this is 40 years old 1975. goodness. I Mean you know that's just incredible And look at this.

It looks like it's a very nice little that's obviously for the internal battery because this thing did have a battery and that's probably where all that Gunk came from. so there's a cut out in there for that. But apart from that, look at this. it's a nice little, uh, sort of cube construction.

Oh well. yeah, there's a board on the bottom as well, so there's board on all. Well, no, not on this end and not on that end. But all four sides are wrapped around like that, so that's really quite neat actually.

I hope they can pull apart I hope they're not. So oh no, yes they are. I think they're plug on boards I can just lift that I should be able to just lift those Boards out. So there you go.

Look at. that is a thing of beauty. Look at the tiny little electrostatic CRT in there I Love it. Oh well, it's even earlier than that.

Look at this. Copyright 1973 Tektronix Corp So it's more than 40 years old. Oh can you believe it? Unbelievable. This is like, you know, just after the Apollo uh program finished.

It's just incredible. But look, we have a date code here of 81 I Don't know whether or not it was manufactured in 81 or there was some other mod or something else happened that could have been like, you know, tested by KW I guess um, in 81 perhaps? Anyway, we'll find out that once we get to the date code of the ICS, that'll be a dead giveaway. There's a few adjustments on here too. We've got plus 15 volt adjust I Assume that's uh, some sort of power rail.

we've got charge adjust I've got high voltage adjust There we go. Character spacing adjust over here. This is like a link I believe I've had a quick look at the schematics and I think there was like a jumper Link in there that actually set how much uh spacing you have between the characters on the CRT I'm not sure why it adjusts that, but anyway, uh DC calibration jumper. So there's a jump link.

um DC Cal as well. Ohms are just times 10 gain and uh DC 0 on AC zero and AC gain. Ah man. more adjustments so you can poke and adjustment screwdriver out.

So I'm going to do is try and lever this board out here and uh I'll show you in a oh no, hang on I might have to take those. Looks like those nuts come out all right? No, I'm stuck these things. They do have a board to board headers on here, but yeah, it looks like those nuts have to come out and check out. Also, the classic black silk screen on the reverse side of these boards look at that terrific stuff.

The other ones are actually etched into the copper on there. But yeah, we do actually have um, some silk screen overlay on the bottom and thoughtfully. look, these are the dip packages. thoughtfully.

they've put them, you know, in exactly the right space on the back for servicing. I Mean that's terrific. Somebody was thinking she's just gonna pop right out now Tada There we go. There's our first board that's probably going to have our character generator ROM on there.

These look like your custom uh Tektronix chips, so we'll take a closer look at those. But oh, look at that big ass cap and there's the Money Shot. Two custom Tech chips. This is uh, u270.

We'll have a look at the schematic in a second. This is the character generator ROM So it basically gives the X Y and Z-axis outputs and decimal. uh, Point blanking and all that sort of stuff. and that's fed from this uh, four digit decade counter here.

and you'll see that on the schematic. that's also a a custom uh Tech chip of some description. So look at that and this is so this is the combined analog. Well, it tells you over here, the analog to digital board.

but also the character generators. So basically we're looking at some trim pot adjustments up there. they were the Ohms in DC uh, Volts adjust. Got some Cutler discrete transistors I'm not sure if that's a input coupling cap or the sampling cap we'll have a look at a minute.

Um, there's a funky looking diode package. We'll check that out. Look at that. it's got a diode symbol on there I've never never seen something like that before.

That is bizarre. Then we've got ourselves an Mc1456 Op amp and then going into a 74 L double O Ah, Classic low power TTL 74l series I Haven't seen those in a long time, but that's just doing some uh, latching, uh, stuff they're using for Nand Gates there to do some latching and that's pretty much it. Look at those funky capacitors, would you? They don't make them like they used to. There you go.

Decode the color code. Awesome. And yep, it turns out that's just a dual diode package. There's actually two pins on the other side.

You can barely see them there. so just two diodes in one package. I'm not sure if they're designed to be thermally bonded and matched and you can see pretty much what's happening here. Here's our Xena reference here.

So our 6.2 volt Xena references the Cr217 I was talking about there there. and where is it? They've got it down here as well. So they've got that coupling over to the input to our counter over here. so we've got a slope converter happening here.

You'll see that in the rest of it. And yeah, there we go. Here's our integrator C227 and that is, uh, certainly that one there. So that's our integrator capacitor.

that's why it's so Schmick and uh, pretty much yeah. voltage reference. and then the Ohms adjust here. which is one of these uh, trim pots up here.

and then that's all just going into a couple of latches and into our four digit decade counter. which as I said, is this one over here and our Nand gate says our two Nand gates, There's two latches there. Nice little waveforms on these. Uh, schematics here.

I Love it. They've got voltage test points. Brilliant. They don't make schematics like this anymore.

Ah, but yeah, that's um, pretty much all it is. This is a custom uh, four digit, uh, decade, uh, count or four decade account here, and that. Here's the Uh binary. Here's the decade.

You know the digit outputs here, and the digit outputs are fed into the character generator ROM down here and the character generator ROM. Unfortunately, we don't have any info on that, but it does all the magic and then outputs the Um X, Y and Z axis and that goes off to the CRT only when you've switched it in. Of course, in multimeter mode, it's disabled in scope mode. And then as I said, they've got the decimal point spacing enable uh pin here.

So this was that strapping we saw on the back of the PCB there. But yeah, there's not a huge amount to this. I Mean this is the analog to digital converter portion. It's all old school.

There's no ADC uh chip as such in this thing. It does it using that slope conversion. Terrific stuff. So basically what this is doing here? the decade counter that actually does the counting direct from the ADC.

It starts at zero, counts it up, and gives you your value, and then multi reflexes the output here. and actually then that goes through the character generator ROM So it'll cycle through each one of the digits, and there's the digit transistors up here, and you can see that it would pass each digit directly through to the character generator ROM. So all the character generator ROM has to do is convert that digit into a specific Uh waveform data, but there'd be a lot of magic happening in there I'd Love to get some info on that. If anyone's got anything on that character generator wrong, please leave it in the comments.

Now you can see how they do the Border board interconnect here. They've got like those, uh, sort of like surface mount crimp type pins that are designed to go into normally, like a, you know, a Molex mating block connector. something like that. Well, the soldered those pins directly onto the Border essentially a surface mount soldered them.

I Don't think that there's any, uh, that their through-hole pins protruding through there and these things wouldn't be easy to solder as well. You wouldn't. Uh, just sold of them are freehand. One by one, you'd have either the original board in place like this, or more likely some sort of uh, soldering alignment.

uh jib where you'd plug the pins into the sockets and then solder them in so they're all nicely light, and then you'd pull the board out. And although this thing is a Marvel of, uh, sort of, you know, systems engineering and integration to get it into this. yeah, sort of. They couldn't really go the whole hog and have a proper PCB mounted B and C on here, so they had to have a coax going down there, stuff it in, and insulate the back of this BNC connector down in here.

It's a bit of a shame that they couldn't uh, you know, do that a bit better. but ah well. you know what's a bit of wiring back in 1975. now is it my imagination or is that BNC uh not Factory original I Think it could be a modern replacement I suspect and look at this: This is the mate in BNC hole for that, it doesn't look like it's been Factory Done.

It looks like somebody has hacked that thing out. hmm and check out the mains wiring. I Mean it's all pretty how you're doing and like there's no proper cable clamping or anything here. It just sort of comes out there.

It's sort of wrapped. It's not even wrapped around the post for a bit of strain relief or something like that. This is going to bend in there right at the back uh, neck of the CRT here and then soldered directly onto the PCB Hey, at least it's huge. Used danger, ac voltage and CRT approximately 1200 volt potentials are present under this area.

Here's the main board: I Popped it out, battery charger test point. There you go and uh, ground plus 75 volts plus 15 volts and plus six point plus minus 6.5 volts in this CRT grid bias there and that is our board. Ta-da that's our CRT dry and that's our main power supply that takes the 240 volts in and converts it down. So is it? uh, looks like some sort of uh switching converter or something to that effect and then a bit of that CRT driver business happening there.

And here's a schematic for our main power supply and battery charging board. We've got some. Here's our AC input here. We've got some uh filtering.

Happen there. There you go. Common mode choke Got a bridge rectifier uh, straight on the mains coming across. uh, that's the battery charger converter circuitry that says uh, those diodes and inductors and cap there are on a substrate so I'm not sure.

Oh, inner Shield outer Shield Oh, okay, so this is all underneath the main shield in on the board there I Think that's what they're talking about and uh, then oh look, we've got ourselves a multivibrator there. Absolutely classic until that building block a mile away. And then here's our inverter over here. And now that's all part of the regulation circuitry.

And the inverter, by the way, is hanging. If you're wondering where it is, where's the Transformer Well, here it is up here and they've got it. So they've got it in a separate can there. and that's what this wire comes over and then attaches to this board over here like that.

So yeah, they mounted that completely off board. so once again, you know, not enough room in there. It's got to fit your CRT and everything else. Oh, we've got a little bit of volume left there.

Let's whack our big ass Transformer in there and just wire it over. Not a problem. Bob's your uncle? Check out this little modification notes. Somebody has done this.

Look at Fourth of the 11th 2011. I Downloaded this schematic. so wherever they got it from I Don't know they're scanned it in from somewhere, but somebody's done this hand mod in there. So there you go.

That's a really aftermarket mod. that one. I Think there we go. We can really see those little board to board contact like Molex type pins there.

And yeah, they do have a little tab which goes into the hole in the board there. That's how they hold them in place during. uh, solder in there. but yeah, they don't.

Actually, the pins don't protrude through the other side. so there you go. They could be purpose designed for that rather than just uh, budget from some some connector and the other part of the CRT driver board down the bottom. This is a big board which goes basically the full base of the unit.

It's got a big cut out in the middle for the battery and a couple of more uh trimmers down in there which don't have an external hole on the side, so these would have have to have been trimmed on the bench before they installed all of this stuff. But once you put that board in there, you can't Oh no, no. There we go. Sorry, they've got the trimmer hole through the board.

There you go. so you can actually install the board first and then trim them afterward. but you wouldn't be able to do it once it's in the case. so this whole thing has to lift out as an assembly.

Speak of the devil. There we go. Yeah, it all just popped out of the case very nicely. and you could once you put all this in.

Um, you know, pretty nicely. adjust and trim this thing on the bench before you whack it in the case. It really is quite a lovely assembly. It's almost a work of art.

And here we go. We can see the bottom of this thing and we've got ourselves some red silk screen. now. doesn't that look lovely? Red and green.

Ah, beautiful and danger. 1200 volts Look at this. The PCB designer really knew their stuff. They're marking out the dangerous voltage side of the thing.

all these contacts right around there. Terrific stuff. Oh yeah, I Forgot to mention the Dayco By the way. Uh, 37th week 1980.

So there you go. We're talking late 1980s for the chips. So yeah, certainly this thing, uh, looks like it was manufactured in 81 as it says in various locations around here, there we go: 51.50 is that 51st Week 81? I Think it might be Got ourselves a nice little shielding plate in there from this. CRT this is an electrostatic CRT of course as I mentioned.

so you get no uh, deflection magnetic deflection coil uh yoke system as you get in like a TV or um, you know some of the older instruments we've seen on the blog before which use magnetic deflection. This has electrostatic uh plates and there's no wiring coming in from the side at all. All comes straight out of the neck end here. There's a bit of uh system dodginess going here.

Look, they've got instead of coming across the main PCB it's coming from either the back side of the unit. Over here, they've got this cable over here with a two pin header connector. that's you know it, plugs into a right angle header on this board. Over here.

here it is there. so that's a bit rude. Um I Don't like that at all. So yeah, a bit of a thought.

oops, we forgot that pair. We have to run it all the way over the water. Oh well, let's just run a cable over. Or maybe there's some electrical reason why they didn't do it.

but I don't know. It seems more like an afterthought to be. And if you take a look at the schematics because this is a multi-board design, uh, it's interesting though. this is a very common technique.

If you have a look at some of the numbers in here, you'll see like this is the Uh, ADC and character generator board like u260, Q247r, 246 right? All of the and C's and all of the R's there labeled in the 200s and that is specifically designed so that you don't duplicate designators over the entire design because you know they didn't have like Cad and uh, check-in back then and you know, automated stuff like that. So they go okay. Everything on this schematic will just number 200. Whether it's a transistor, a you know, an IC, an inductor, a capacitor, whatever, it'll get the 200 number series and then you go over here and have a look at this high voltage board.

for example. um, no, sorry, this is the RMS converter board, then everything's in the 100 series. There you go, there's a match transistor, thermally matched transistor pair there q194, 188, all the capacitors of the 100 you know, 167, all the resistors, everything else numbered in the 100 series and I Took that Shield off our high voltage board down in here and haha what do we find? There's our voltage multiplier. There you go, there's our diodes in there and our caps for our voltage multiplier.

We can have a look at the schematic over here here. It is classic topology and uh, and we've got some handwritten notes up here. There we go. Um, it should never exceed 450 volts.

This voltage is highly dependent upon the battery. Uh, the the condition of the battery. So there you go should not exceed 450 volts. Somebody's hand written uh, quite a few things on this schematic here, so that's rather neat.

But there you go. There's our high voltage multiplier right under there. Well, hey, look at that. We have ourselves a high of orange ceramic resistor in there by the looks of it and uh, with its own little uh, insulated wire going all the way back over there.

That one was most likely I Can't see the silk screen on the back, but most likely that 100 Mega resistor in there? There you go. Unfortunately, it looks like we're missing the schematic for this baseboard here because it's got uh, part numbers in the 300 range and none of the schematic sheets I've got here actually have the 300 range on them. And it's a shame because there's a very interesting little uh packaged IC part around here. I'll try and get at it I might have to take the CRT out for that.

And there you go. I Popped out the uh CRT there and well, we've got a socketed uh, strangely RCA chip I Don't know why it's uh, socketed, but yeah, it's got a weird ass part number on it. And check out this puppy down here. Another tech custom part in one of those weird ass packages.

And if course, I'm going to show you a close-up of that, why wouldn't I look at that. Beautiful! Now here's the main function board. Nice classic ganged switch Arrangement here. Just beautiful.

Uh, a couple of you know, boggy mods on there. Look, we've got some resistors, all series stuff. Some caps go from there to there. That's obviously some sort of afterthought.

They've decided to whack that on there. You know, even some wire in here. why they haven't got that on the board? I Don't know. did they run out of space? Who knows.

But anyway, um, yeah. quite a dense little. uh Arrangement here. once again, more board to board interconnects top and bottom.

So imagine trying to design this system from a cube. Arrangement I've designed these actually full cubes where there's boards on all six sides and trust me, it ain't easy. Even doing a four board wrap around like this and grounds can be a real big problem and things like that. So yeah, real pain in the ass.

but anyway, that's a quite dense little ball then that's obviously. uh, the front end is on the other side of it over here and unfortunately I may not be able to get to that ball because I can't figure out how to get all this plastic um off. I Don't seem to see how it's all held in there. so yeah, I may not go to the effort to actually, uh, do that.

but anyway, um yeah, if you want it, it's just more of you know, it's more similar construction. Although we do have our rotary Uh switches on there and you can actually see the mechanism. There's part of the mechanism there, part of the contacts there, and other parts would be that metal right in there. with that those through-hole terminals in there that would they'd have contacts in there and that'd be all part of the Uh that switch.

That's the Uh volts per Division and also the Ohms and range selection and things like that. So that's a multi-purpose switch. Real complex, custom arrangement in that oh nasty business. And as for the scope, uh, front end here.

Well, it is a basic analog scope front in Asia To find in any scope. here's the probe here. We've got our selectable AC DC input coupling here. We've got our input resistances with our frequency compensation, as well as a 10 Meg input resistor and pretty much that's coupling into a match start Jfit input pair.

So yeah, pretty odd. You know, just a run-of-the-miller stuff. It's only got a bandwidth of one megahertz. Nothing fancy going on here at all.

Basically, the only thing you're not going to find in a classic analog scope is the switching to switch through to the media. You can see how it switches the probe through here, or it switches it through to some of the multimeter input circuitry here. Here's the Milliamp Ohms. Here's the Ohms current Source right down here and then likewise on the output of the input buff and the Jfet input buffer here.

Then we've got some switching that goes through to the analog. R DMM circuitry all the vertical circuitry here, so it just switches that through whichever mode you're in. and it's got all the rain switching stuff up here. It's showing all that, unfortunately.

I Can't see the rest of it here because somebody has included some sort of modern circuit here. and um, yeah. I'm not sure what relevance that actually has, haven't looked into it, but yeah, there's obviously some more, uh, vital stuff missing there because we've got these switching lines going up here. so they're going up to some sort of switching diagram up there.

or something like that, perhaps. So so yeah, I Don't think there's a whole lot of insight to be gained by ripping apart all this modulus scene that top side of the input board there that actually has the multimeter input terminals. They're soldered directly onto the board in there. There we go.

It looks like that might be some sort of, uh, ceramic, um, uh, resistor divider module that you'd find in any multimeter front end of the day. so you know. Yeah, pretty ordinary type stuff. The pots are mounted directly on the board, down in there and the switches down in there.

and there's some shielding on top of that as well I Believe coming from the other side. So yeah, that's about all she wrote for the input circuitry on that thing. But there you go. That's pretty much the tear down.

In a nutshell, look at that. that's CRT. it's just so cute. Look at it.

Ah, thing of beauty and a joy forever. So there you go. I hope you found that tear down of the classic 1975 vintage. even that was built in 81 so it had a bit of a life there.

although I don't think I had much of a life after 81 probably I don't know. but if anyone's got a final um, you know, build or a sell date on this thing, then please let us know how long was the product lifetime? Anyway, that was Techtronics 213. Uh, portable, not really pocket, but portable multimeter slash DMM and this thing would have been killer in its day. And you've got to remember, this is practically 40 years ago and it still works.

Unbelievable. Still a Marvel of Technology Really? I Mean you know there's not much more you can you could like. If you had to do it with a CRT this day, then these days the CRT is not going to be any smaller. Pretty much and pretty much you can shrink some of the other circuitry, but it's not going to be a hell of a lot smaller.

So there you go. My hat's off to the Tektronics designers back then. This absolutely fantastic design to package. All this and you know, systems engineering that goes into creating that Uh, Cube Arrangement that four-sided border management or interacting and board-to-board interconnects That ain't easy folks I Can tell you so very very impressed I Hope you enjoyed that and if you did, please give it a big thumbs up.

And if you want to discuss it, please jump on over to the EV blog Forum or leave a comment on YouTube or in the blog comments I Do read all of the comments I Try doing I Try to reply to as many as possible even though it takes me a lot a lot of hours to do that. Oh well, it's good fun. I Love reading the comments. Catch you next time Foreign.