Hi, welcome to tear down Tuesday And yes, Vintage Calculator Time you know I Love vintage calculators and I Love HP calculators and uh Darna Kindly sent this in in the previous uh mailbag segment and it is the Classic Hulet Packard 41 CV Calculator The One The well. the world's first Uh calculator with an alpha 14 segment alpha numeric display. It had lots of first keyboard overlays or uh, programmable keystroke programmable, all sorts of things classic calculator and had a very long product. uh, lifetime.

It came out first, came out in 1979 and was wasn't discontinued until uh, 1990 or so. so so more than a decade product lifetime for a calculator like this is just phenomenal and it is an absolute classic and we're going to tear it apart and see what's in there. This one's got the four slots if you want wondering what the Uh model number? uh well, the CV actually means 41c was the original one and you used to be able to buy a memory expansion pack to go into that, but then they released this CV model. The V stands for five of course.

Roman numerals and uh, that means that it's got five times the memory of the C model. So this one effectively has that memory expansion uh box, uh built into it. So here you go. We're going to take this thing apart and really is very well made.

And if for those playing along at home, here's the uh serial number and somebody a uh HP fan obviously on uh YouTube sorry I forget your name but they said uh that trans serial number translates to I think the 6th week in 1988 it was manufactured and the S stands for Singapore So this was manufactured in Hp's Singapore Factory missing a rubber foot there and I love the battery holder like this. Look at that. it's just brilliant. 4 n cells in there.

Great battery holder. If you've seen the previous video, you know it's got the little uh levers, uh sort of little spring. Yeah there it is inside there to sort of, you know, hold the battery in place properly. Really beautifully designed battery compartment and one of the interesting things that we're going to take a look at is the use of flat Flex cables in there for the battering contacts and also for the expansion module contacts as well.

If we take a look down in there, look at that. I mean that had to be an innovation for its time as well. So this particular one is uh, 26 years old and it'll be interesting to take a look inside of it. But you got to remember I Don't think they uh, really updated the design in any Uh Major Way since 19, Uh 709 and they would have designed it even before 79.

that was when it first came out. Now unfortunately, all of the Uh HP Fanboys are having a fit right about now by me taking off the original rubber feet. Unfortunately, we have to do that to get at the four screws and presumably the four screws will hold it together. It's really, is, uh, quite a solid Um unit.

by the way, it really, um, feels quite solid. Very lightweight unit. but yeah, there's really that is quite a rigid case. So I expect there's more than there's might be some um, snap holders around the outside of, uh, the case or something like that.

That wouldn't surprise me. So let's take the screws out. Of course, the extensive use of flat Flex Cable in there for those contacts, which was quite remarkable, indicates that this is going to have a high level of Uh Technology Innovation for its time. I mean the 14 segment LCD was an innovation in its day.

Oh, tiny little screws at the front and uh, well, it's going to have, uh, almost, maybe all SMD although there could be um I'm not sure if it's going to be like an all uh Flex PCB I probably I I Don't know it could be with like the main Uh processor, uh, the custom processor mounted on the flat Flex I Don't know, but it could very well be a standard. Here we go: F R4 yeah, standard Fr4. There we go. standard rigid PCB and oh, there we go.

Just some pressure contacts down in there for the there's the flat Flex up there for the expansion and uh, it's just relying on the pressure of the case. From where the screws are, they strategically put the screws right next to the to, right next to the connector there, so it just makes contact with the gold pads down there on the board. So um, that you know some thought went into that. obviously they weren't if they put, say, the screws up here or something like that and just relied on the rigidity of the case to get even pressure contact on those.

uh, on that flat Flex there, then that wouldn't have been. uh, you know, very good design at all, but that one's quite nice. They've almost. You know, they've really put some thought into that.

We're going well. these contacts are pretty critical. Going to these expansion head is we can't have the casee like flexing like I was doing before you know it be dropped or these screws come a little bit loose or something like that and have bad contact. So that's really good putting the two screws there.

There's our main is that our only device on this whole thing I doubt it. We'll have to, uh, take out the rest of it. Oh no I see some dreaded heat staks there I don't like the look of those I hope we don't have to, uh, drill or cut out those heat Stakes to get into the the main? uh, uh, to see the other side of the board. But oh yeah.

anyway. um, we've got ourselves a cap here that was, um, obviously storing the charge so you replace the battery so you don't lose the contents. Um so they've just got a large value cap in there. Bit of a bodge going on here.

Look at this. Check that out. Hey look at that. looks like a they have got a couple of dodes there through hole they've bodged that wire in.

they've put some heat shrink over it, little tanel on there, little blue taning going on there and a wire coming over to here. that's pretty how you're doing and they've yeah, they've uh scraped off the trace there on the PCB. So I wonder what that mod actually is? Is that a factory mod and aftermarket mod? I Don't think it's a it must be a factory mod cuz I think those um feet rubber feet were actually original? So yeah, that must have been a factory mod huh? Go figure. Didn't expect to see that and you can see the uh flat Flex there.

you can see how they've got the gold that would be top Quality Gold by the way, that wouldn't be. you know, really skimp like they do these days on some products that would be really heavily plated uh gold contacts on there and exposed for the uh contacts of the module that plugs in the back here so that one goes onto the main board as we saw before. and then that's like the Uh Edge contacts for the expansion uh module at the back there and then right along the edge. There's your battery contacts right in there, so that's you know.

I I Think that's a really nice elegant way to do it I You know I Don't know who would have, uh, you know thought of this. Uh, in terms of you know, the plug-in modules at the back and for the battery holder as well. It really is quite an elegant system system to have that sort of allinone module like that. So something like that is not the first thing that would spring into a design engineer's mind when you got to come up with a product like this.

I mean back in the day we're talking, you know, the late 70s Here this was probably designed in like uh 78. It came out in 79 so you know, would have taken at least a year to get this thing into into production for sure. And uh, you know back then somebody think, well, how do we do it You know we've got ourselves a PCB Well, you put some. you know, first thought would have been to stick some, you know, right angle uh module connectors on here or something like that.

but then they went well. no, we got to plug the battery in and well I don't know, you know some Op compromises and optimizations. later they come up with the idea. Well I got the flex in there.

Well, we're using it for the modules. That's a great idea. We might as well whack the battery contacts in there as well. Brilliant.

Curiously. Uh, that comes out as a separate. that spacer. There comes out as a separate uh, part of the case.

Look at that. It even tapers down. H Nice. I Am quite surprised that they went for just the dicky you know hand soldered piso transducer in there.

That's I Don't know why they didn't use spring contacts that that would have been. you know, look completely a wireless. Um by Wireless I don't mean Wireless as you get today I.E There's no wires in the thing um, designed to hand wire those. You know that in is just sort of ruins the Elegance of it.

really. You know the mod side. uh and things like that, it just spoils it I think I Don't know why they didn't use those Springs and I spy a secondary board down there for the LCD. Obviously, these tabs here are holding that LCD module in place along there.

That's what that part number would be for the on the LCD module itself. Date code there. We go 47th week 87 so that is H Confirmed. That's when that module would have been manufactured and date code on the main Uh chip is very similar as well.

So there you go. But look, there's an extra Uh cap solded down to that board down in there. And there is the processor. and yes, that is uh HP um marked into there.

stamped into there. Awesome! And uh, this is for those who don't know about the HP calculators. These are basically a a BCD Uh based processor uh 56-bit register in the HP 41. This processor is the Uh precursor to the Saturn the famous Saturn architecture, but they're all based on the same sort of architecture going way way back.

and this particular one actually had 14 4 bit Uh parts to make up a total of 56 bits for each register. and the data was stored in there in BCD format. so it could give a in those Uh number of Uh bits. For bits per Uh digit, you could get a 10 digit mantisa and a two-digit Uh exponent.

Now, curiously, this seems to be the only chip on the board. The bottom side seems to be completely devoted to the Uh keypad overlay. So I think everything is within this tiny little Uh quad flat pack. This custom quad flat pack, so I can only presume that the Uh CV model actually integrated the extra five times the number of registers into the particular chip.

They actually respun the Uh ASC itself for the CV model over the standard Uh C model. I Wasn't expecting that I Thought it'd have the same process and they would have had the separate Uh memory chips on the board. but no, clearly not. and interesting Point to note is that they've got one little tiny pin on each each side there not on this side, but on either side here.

actually. uh, chopped out and uh, that almost looks like it's a hand drag solder job actually rather than Reflow it does not look like a reflowed solder joint at all If I really get in there. If I really get in there, you can see how the solder is sort of pardon the pun dragged up at the end there, so it's almost as if somebody's wiped the iron across there. and these are like hand done.

And of course there's no um solder M between uh pads on there. So yeah, I guess you had to be a little bit careful. so that's interesting, especially in uh, 1988 And you'll notice that around the board, we've got some uh Square test pads there there just scattered around various points. obviously that's for some sort of, uh, bed of nails.

uh, production tester there. So yeah, these would have been uh, you know, sat upside down in on a bit of nails and uh, Factory tested in some way to exercise the processor and make sure you know the display works and everything else. now. Unfortunately, to get uh further into this thing, yep, I mean I can't lift that board out there.

This is classic uh, calculator construction where they use all these little heat Stakes Here they're actually molded into the main case, they poke up through the board and then they come along and they, uh, heat seal uh, the tops here or they cap the uh Tops on them so that's actually holding down the board and you might be asking, well, why so many spread over that grid? Well, to get of course, the rigidity in your keys because you know that classic HP you know, clicky uh key feel. Of course they have to get that just right. And there's actually quite a bit of art that goes into getting that HP calculator feel and they needed that many Heat heat Stakes All spread around here to get the rigidity they required in the keyboard there. You know you can't have one little spongy key on one side or something like that.

Ah, that'd be horrible. So unfortunately, um, to look at the bottom I'm would have to take out, drill out, cut out all of those heat stakes, and pretty much ruin this pretty much. um, you know. uh, almost.

Mint Condition working HP 41 SE I Don't think I can bring myself to do it? Oh, if you really, really want me to do it, leave you know, say so in the comments. Should I go any further or should I or should I respect the beauty of this HP calculator H But I can see through the board in there. you can see like the ring pattern on there for the tactile Dome So you can see that you know this this. Trace over here for example that goes through that via there to a pad ring on the top side and then the tactile Dome is probably uh, solded onto the top.

They're probably they might even be a reflowed uh tactile Dome I'm not actually sure how HP do it in this 41 CV I'm sure the uh HP Fanboys will, uh, know, will, uh, know, no doubt. and they will, uh, be able to provide some info cuz I can't find that out unless I actually butcher this thing, take it all part and sacrifice it for a YouTube video. Oh no, I don't want to I don't want to. And same thing with the LCD module down here.

There's obviously something I mean these these? uh, we've got uh, some pin. you know, like a little pin header here. obviously that looks like it's going down. solded on either side here, solded down to the LCD module there.

And of course, there's not enough individual segments. So clearly there's obviously, uh, driver chips inside here under this sort of, yeah, that's like a ceramic or potted uh, you know, case on top of there. So presumably there's all the driver chips in there for the individual segments and they've just got, you know, serial lines coming over here and they probably snake back to the processor somehow. So yeah, the processor is probably driving that LCD module uh, serially I'd say and uh, there's got to be some segment drivers under there, cuzz, just not enough pins on this processor of course to drive uh segments.

It's just not going to happen. so there's some additional uh processing or um, or at least SE serial to parallel uh segment drivers under there as part of that LCD module and I can you know try and lift these tabs up? but that's not going to be of any use at all. cuz I have to get the whole board out in order to see that? Bummer. and aha, if we look carefully down the side there, you can see the tracers coming out from one of the main chips under here, from that segment driver chip going out to the Uh segments for the LCD and you know there's probably some uh, zebra, uh strips in there to make uh contact with the LCD glass.

most likely just like you're familiar within any um modern LCD product. So I'm sorry folks, but that's all I can show you inside this classic HP 41 CV Because well, I respect this thing too much to pull it apart. uh, you know, destroy it to just see the lousy bottom side of the board. and well, that LCD driver Chip's probably potted anyway.

you'd have to, uh, dissolve that away to see anything. Oh I Can't bring myself to do it unless the will of the community decide that this calculator must be sacrificed for the means of getting. Well, not much further information, but oh well. I Hope people will vote to respect this thing just like I want to.

So there you go I Hope you enjoyed that. That was a very brief look inside a HP 41 CV calculator. this particular one about 24 years old or something. No 26 years old or something like that.

but this one dates back even further than that uh, originally 1979 design and people still use these today. Fantastic calculator. If you want to discuss it, jump on over to the EV blog for and I will also have some um, highres photos of the tear down available at Eev blog.com as well. So go on over to the main website to check those out.

Catch you next time.