Hi welcome to Tear down Tuesday Yes I think I'm officially a vault nut. What is a vault nut? Well, anyone who has an 8 and 1 half digigit multimeter pretty much I think that's probably the definition. and yes, I've got one. I foolishly went and bought an eight and a half digit multimeter.

No, it's not a the classic HP uh, 3458 of course, which is the world's best, but this one's not bad. It's an oldie, but um, maybe a goodie. We'll find out. anyway.

it's from a company you've probably never heard of. they're called Prema uh and they're still around. but they're like a semiconductor. uh, company basically.

and they specifying, uh, specialize in what semiconductors. they roll their own, Adc's and things like that and uh, DC voltage standards and well, back in the day in uh, this case the late 80s, they uh designed and sold an 8 and 1/2 digit multimeter so got this on eBay and well, I'm I don't know I Just got it from the post office and I'm a bit horrified by the lack of packaging. You can just tell by the physical size of this cuz these are large multimeters so they can't be much in the way of packaging in this thing. and they person at the post office went out the back and got it, bought it back, and sort of tossed it down on the counter.

It sort of went thud and inside I just went and well. yeah, I don't know if it's made it intact. That's one of the things with buying test gear on. eBay Not only do you Not know if it works or not um and is still within spec, this one I think was um, sold.

As you know, it powered up, but it was. You know it hadn't been tou that have been in storage in a case or something since it was last calibrated or something like that. so you know a reasonable level of confidence that it's going to work I think but certainly not guaranteed. Um, and obviously they clearly don't know how to package uh, test gear properly cuz I don't think there's much in the way.

We got a box in here and oh, anyway. uh yes, The thing is, you don't really know on uh eBay what you're going to get or how they're going to package the things even if it is good when it get shipped around the world like this. Who knows, you know. Just yeah.

tossed on the counter at the local Australia Post Office But hey, what happened on the 747 flying here and the cargo hold and the baggage handlers and everything else? Well and not baggage handlers? The commercial uh handlers I guess. but gee. I don't know. Only one way to find out.

Let's take it apart. unfortunately. I'm not going to have to do the uh, don't turn it on, take it apart thing I'm going to have to plug it in straight away and see if it still works I think but after that we'll tear it down. Let's go.

All right Here we go it. and uh, there, there's bubble wrap in there. There's going to be like one layer of bubble wrap or maybe two at most. Um, but you know, usually when I get test gear like this and if it comes from a good, uh, you know, reputable test gear uh, reseller for example, they will know how to package it and they'll like a vacuum, uh uh packet in the you know, the um, custom uh, foam or something like that or at least heavily pack it in uh, you know, foam, peanuts, and things like that.

But this is really quite hotch poch. and yeah, look, there's one or two layers of thin bubble wrap. and of course the um, look nothing on the the corners here look nothing on the corners. So the problem with that when you ship things like that, um, all of the shock gets taken on there.

So when this thing gets, you know, thrown around bang, you're really going to get the shock transferred into here. and then of course that being all originally mounted inside, that's going to transfer through to the Uh PCB inside. And curiously, it's got a bit of cardboard in there as well. So I there we go.

They've at least done the right thing. And at the very least, they've put cardboard covering on the front panel so that's not too bad. Okay, I'll give them props for that. They've at least, thought of that, but they haven't thought of uh, transferring that shock through to the Um through to the Shazzy.

But it doesn't look physically damage, so looks like it's made it in one piece. Woohoo! Will it work? I Don't know. So yeah, it's in reasonable. Nick I Don't mind it at all.

Looks like the uh cow seals might be, uh, broken on the thing. but yeah, really old school look of it. Look at this. uh, old school seven segment red lead display in the old illuminated push buttons.

Really old style banana jacks on these things? I mean check that out that is just old. that's really old school. uh shrouded banana plugs and a couple of more seven digit displays. But uh, seven segment displays.

But well, let's Power It Up This Is By the way, the 6047. There also is a slightly higher spec 6048, but this is 8 and2 digits. uh one? PPM Stability or thereabouts? Uh, short-term stability I Think the 6048 is uh .5 PPM Stability I Will link in the manual for this thing. uh, down below.

but I did get a full manual with it, so that's uh, that's pretty good. Got the original printed manual? Oh look. Schematics Schematics: Awesome. We got the full schematics I haven't checked online if the online schematics have.

If the online manuals have the schematics, but look, there's the whole front end and there is the ADC There it is. look uh, they rolled their own custom Prema um ADC in this thing. So yeah, there you go. I Think this uses either the LM uh 399 voltage reference or the LTZ 1000.

I think the higher end one might use the LTC Zed 1000. But anyway, let's power the thing up and uh, see if it works. And yeah, that cow seal looks slightly broken. Ah well.

and on the back there's not much. uh, it looks like I don't have the multi Channel option on the thing, but there you go. I've got serial number 1,041 they didn't make many of these I'm not sure of the exact age. there's no date code, but we'll find out from the chips inside.

and it's got a Gpib and a external trigger using a a 3 and 1/2 mil. Jack and uh um, standard. uh, two foot. well I don't know if it's Universal ah no, there's the voltage on there I have to switch that around so better make sure I get that right.

other don't to blow the ass out of it. All right here we go have: I bought a dud controller one. whatever that is, but that's promising. That means the processor is working and it's booting up.

controller four. whatever. Hey, there we go. We're in.

We're in like Flynn It's in milliamp mode but uh, volts. DC There we go. 200 M volts There we go. Let's switch to 2vt mode.

Obviously it's got high input impedance because it's counting up. So there you go. Excellent 200 Volt range. There you go.

Once you get to 200 Volt range, it's not high input impedance anymore, so that's why it's uh, quite low, but you switch it down to 20 and yep, it's got that high input impedance now. just a very quick check with my uh Little Resistance box here. 10K it's around about that, you know, down to the fourth uh digit there. pretty much let's whack it in here and see what we get.

20K Yeah, there we go. Hey winner winner chicken dinner. It's interesting that on the resistance range here, if it goes over range, it actually tells you Arrow one I was a bit mortified when I first switched on the resistance range eror and here we go. I've hooked it up to my 10vt uh EDC lab standard here, but I just plugged it in like a minute ago so really nothing's warmed up and re and the uh and the Premier 2 has only been on for you know, 5 minutes or whatever.

I've been filming So yeah, we're a little bit out, but our agilant is uh, much closer there 996 whereas uh, down here. Yeah yeah, it's a bit out, so whether or not it just hasn't warmed up yet I Have no idea I have to leave it going I Haven't you know to do proper performance tests on this could take days or something. It's not easy, but it basically uh, works so you know whether or not it's within spec cuz we're talking um, the Agilant 34 61a, 6 and2 digigit multimeter typically in the order of 05% Uh. accuracy.

in terms of like a one-ear accuracy this Prema 8 and 1 half digits. um, two full digits more? Uh, pretty much. although this is 10,000 count. Anyway, this is 8 and 1/2 digits go goes up to 20.

so it's 1 19999. Um, and it's in the order of 05% so an order of magnitude 10 times better. Uh, basic DC volt accuracy spec than a 6 and 1/2 digit top of the range 6 and a half digit metal at the Agilant 34 61a. So that's a sort of, you know.

even though you're jumping up two digits, you're only jumping up one order of accuracy. Pretty much yeah. and BAS basically the same on the 1V range as well. Look, the agilant pretty darn close to spot on.

and I've done previous videos on this this thing I've taken it to the local cow labo actually linking that down below and this thing is bang on when you let it uh, warm up. but yeah, look at that point n99 so we got 5 9 There we go over to here and we're on the 2v Range9 98. so yeah, something's out I don't know. as I said, got to let it warm up.

do some more tests, but not that great on the DC volts. I was expecting more I don't actually know how to switch in the extra couple of digits here. Don't know how to work this thing. uh yet.

You know it's got all sorts of measurement, uh, modes and inte. you can set the integration time and all sorts of stuff that would do it. Um, by changing the integration time, you'd uh, likely get your increased resolution there. And if you're curious to know how much uh Power it takes, there we go.

I've got it hooked up to my uh power meter here and it's taking about 16 odd Watts or thereabouts or 18.5 VA woohoo with a power factor of 863. Terrific. Well, it basically works so there's only one thing left to do and that's take it apart Now of course, what we expect in this sucker is uh uh, pretty much uh, you know, late 80s vintage. So we're looking at all through hole uh, components or dip package.

just stuff like that. I'd be surprised if there's any surface mount in here. Um, because they wouldn't have optimized this for manufacturer, that's for sure. This is only serial number 1,000 so not not exactly huge.

Can I lift that up? Here we go. we're in. Oh look at that Beautiful. Check that out.

Three boards and oh hang on, hang on. Oh yeah, Vintage Precision Test equipment smell love it. Well it looks like I was pretty bang on when I said they wouldn't have optimized this thing for production. They sure haven't.

Look, uh, this is sort of the construction you'd find in sort of. you know that one awful low volume uh test gear you might typically or I've typically designed in the past for like, you know, production testing and uh, stuff like that. Y you man want to manufacture 10 of them? You know? this is probably what you'd end up looking like. look.

three separate boards, just sort of, uh, you know, tied into rails down on the bottom. there. it looks like they got a couple of rails through there. Just a couple of standoffs, so nothing fancy in that respect.

No fancy mounting or anything like that. By the way, there's no fan in this thing. um, at all. Uh, completely silent as you saw it.

Only draw Drew uh know, 15 odd Watts or thereabouts. But anyway, uh Transformer up here, right? Uh, right hand board construction solded directly onto that. Then a little board. very nice looking board to board interconnect there, and uh, looks like out the air there's our main uh, voltage reference.

There couple of huge reays in here, but really, just double-sided board construction. We got all our processing happening over here. Good old Eom in there. Don't want to lose that uh, data out out of that, you may not get that that uh back in a hurry.

Ooh is that a real time clock chip? One of those Dallas realtime clock chips under there? Perhaps. But yeah, we've got some uh Precision uh. front end stuff happening over here. We got it under under a shield.

but yeah, nothing fancy whatsoever. So uh, socketed. Everything is basically socketed. uh, looks like we got some Precision foil resistors here.

They look like V ones. uh Zed foil construction if they were around back in the uh, late 80s. but that's what they look like to me. and um, yeah.

I it's just basic through old technology. nothing fancy whatsoever. all off-the-shelf parts. This thing would be entirely repairable, especially when you got the schematics.

even without it. Gez, you could easily trace this cir out circuit out and figure what it's doing. unless of course the custom ADC which is probably under here I See a a couple of custom chips with weird ass part numbers. They're most likely uh, Prema Uh custom chips because they are a silicon company and I know for a fact they rolled their own analog to digital converter inside this thing and it's all about how you're doing too.

I Mean we've got this single in line thing I have to look at the other side, but it's just bent over at an angle there. Look at these. uh Precision uh resistors here. There we go.

like there, they're only 1% Of course they're not high tolerance, but they would be, you know, practically zero. Tempco zero drif in these things because you know they. they probably paid a couple of hundred bucks each for those resistors to get them. They probably got the best V had to offer at the time.

And yeah, nothing but the best would have gone into these things because the drift in this unit as I said even in this unit is 1 PPM So that's its. uh, nominal, uh, drift spec or something like that and the higher end one is half that at 0.5 PPM or something like that. And look, then they've got this this metal can package just bodged into this dip socket up here and it is all very handmade. It's not like this is, uh, you know any sort of, you know, high volume production at all.

Probably each one of these was individually handmade to order most likely. and I think that is the widest clearance I've ever seen on any standoff. uh, uh, bolt at all? Look at that. They were really paranoid.

Let's not go anywhere near those suckers. Could be guard tracers on there. I See, a couple of these are missing the solder mask, so that's what they could be doing there. And you find weird stuff like this.

There's a 748 C 4046 there and just a crusty single turn trim pod on the board. You think you know this doesn't look like a Precision World Class 8 and 1 half digit? DMM that's for sure, but it is because you know that's not the important stuff. All the important stuff is happening under here here. and get in, you know, zero Tempco uh, pretty much cuz uh.

once you've got, you know there's you know. Whack some high quality relays in there, some Precision resistors and then you get a Precision hand selected hand age no doubt uh, voltage reference in here and you combine those things together and and with a uh Precision ADC which they've rolled their own in this thing, we might be able to find it eventually. and uh yeah, Bingo you can get 8 and a half digit performance. Doesn't look like it.

just by looking at this thing. You wouldn't say that this is you know any sort of precision instrument at all. And bingo Date Co we're talking. you know, 41st Week 88 That's probably like the oldest or the newest.

sorry I can uh find in there. some of them are quite old. like look at this. over here, we're talking.

you know? 85 34th Week 85 Gez Although the um, look at this is that 91 I guess was the last ROM code on there. oh look that's coming off. Check out some of the soldering on this. Looks like somebody's had a hack at that from the top.

Almost as if they've replaced that diode in there. I don't like the look at that at all and similar things you know happening up here. That's just that's just not great. There's like they've been bodged on and hand solded.

Some of it looks uh, you know, like it's prop wave solded and then other things look like it's been bodged on. Maybe I've got one that's been repaired perhaps? And that black single in line package we saw before. Aha, look at that 100 milliohm shunt resistor. Once again, it's only at 1% The absolute accuracy in these things does not matter.

It's all about the Tempco So Zerin I don't know I can't pronounce that Isabel Sho I don't know. Can anyone uh, name the manufacturer or get a data sheet for that sucker? Woo! Never seen that before and all throughout this thing they using uh German SDS reays. So top quality and of course in a Precision 8 and 1/2 digit multimeter, the connections matter like the physical material uh themselves. Once again they will probably be uh.

torium copper contacts, really expensive, really high grade. you don't want any uh voltage differentials in there at all. And of course here are our custom chips dead giveaway their marked PR which is Prema obviously uh designed and manufactured being a silicon company and this one's got bk7 I don't know, you'd have to look up the uh manual and uh schematic for that one. And of course, as far as the power supply, uh goes here.

Nothing fancy at all. They're running a couple of TAPS off here, all nicely heat shrunk and they got uh cardboard in here actually protecting that uh Main's wiring stuff so that's really pretty good. Then we got a a big bridge rectifier here. Uh, we got a small PC of be mounted well small is for a to Um 3 package.

anyway to Uh 3. yeah, it's an LM LM 309k. There you go. and then uh, just a big 4700 mic uh filter cap.

so you know your traditional linear Supply just generating the 5 volts needed for all this stuff. And then of course they've got the board to board, interconnect connector down. in. there.

There it is. It's very quite. It's quite nice actually. I Rather like the look of that one.

and um, yeah, just some small linear regulation around here as well. Once again, you need those for the plus minus rails and of course opto couplers for everything. As you'd expect, that connector is all just on an angle there. really dodgy throwing together.

It's quite a mate. Yeah, here we go. these are all on an angle like that. Uh, anyway, here's your opto couplers here.

So between your digital processor board over here and just this, this could be part of the sampling uh, logic. All your analog is going to happen over here so you expect to find your ADC over there. but it could no actually based on those kickass looking sampling caps in there I'd say that's our analog to digital converter without having to look over here. So clearly they've got to get the signal over this.

these ribbon cables here. um, but you know it's going to be sort of F level type stuff, so that's probably our custom ad set our in integrator um ADC down in there and Opto couplers and opto couplers out here as well. This is just to get some, uh, probably some Digital Data over to drive these relays. all this relay switching over here.

It probably go via these Opto couplers here and then your data output serial of course. CU You haven't got enough lines there for parallel. so serial data out of your analog to digital converter straight into your processor board over here. Well, I Took the shield off this thing and look at this.

We've got more bogginess. I mean take a look at that. it looks like we've got some uh, what looks like poly sty in caps just like Bodgy W, you know, paralleled up there. and we got a couple, you know, just afterthoughts just added across this resistor divider here.

uh, you know, probably doing improve the AC uh performance of that thing. and well, it's it's pretty crap. Look, we got ourselves some uh, nice trimmers here. These are all uh, available through the top of the can there.

Uh, these little re reays in there I Suspect they could certainly well be re relays for uh switching in there. but yeah, jeez, it's really just sort of throwing together hotch poch. Not professional at all and no surprises for finding the Classic 8637 true. RMS converter I see that's been used in every multimeter since day dot and as I said before, Voltage Reference Classic LM 299 Ah, there we go and it's not that one of those uh Rebrand ones.

as I said the uh upper model to this the Um 6048. it's I believe. Got the LTZ uh LTZ 1000 voltage reference in there so that one's slightly better than the LM 299 used in this one. but as I said, that would have been hand selected, hand aged, all that sort of stuff so only the best would have been placed into this thing.

probably individually serial numbered maybe? I don't know I can't see anything but yeah, they certainly would have been handpicked. The thing I Find very interesting about this is all of the sockets in here. even for all your Precision Parts they're just crap sort of looking Jewel wipe contacts. not even doesn't even look like they're goldplated at all I don't like them made in West Germany I presume See, there's some of that horrible hacked on rubbish.

those polystyrene caps just solded across there. Oh man, there a bad taste in your mouth. and if you wondering what that puppy is down in there bodged into the dip socket, it's an LM 343 high voltage Op amp and you can see an example of the Guard traces. This one is for the Ohms range.

So there you go. These ones are. That's the guard Trace going all the way around there as uh seen in previous videos to stop uh, leakage between critical nodes. Now of course, all these trimmers you see in there, they wouldn't be setting the Uh references, they're just uh, trimmer caps in there designed to, uh, just tweak the ace uh performance of each range.

Oh, look at that PA of thermally bonded transistors. They're in love. Wonderful to see. There we go.

We got ourselves a hand serial numbered Uh ceramic resistor divider or high voltage resistor uh Network in there. So yeah, it would have been individually tested and characterized, no doubt coax so well. What can you say about this? I mean I Expected a a bit more spit and polish for a 8 and2 digit you know meter of this sort of Uh performance. you know it really is quite Kick-Ass performance especially for its day, even even today.

it's a really top uh, you know, spec unit now. uh, whether or not it's still within spec I don't know cuz as I said, there is a uh nonvolatile RAM up here and that could be keeping the calibration constancy. I would have to read the manual and see how this presumably it holds the calibration constants in Uh software in there. and you could you know during uh, during Uh Factory calibration or re calibration adjustment of this thing, not just calibration check, but calibration adjustment.

They would uh Program in those uh calibration factors into there so they could be lost. So that's maybe why it could be on very quick initial testing, potentially out by a little bit, but uh yeah still. Anyway, that is just a it's just bodge cenal. it really is.

It's like they just, you know, slap these together by hand. Not a huge amount thought thought given into the production side of things and the spit and polish. but hey, you know it goes to show that you can make an an 8 and 1 half digit. you know, world class performance.

deal in DMM with you know this sort of uh, simple construction technique. if you know what you doing, anyone can do it. but hey, there is a bit of secret source that goes into that custom Asic analog to digital converter there and that's where the manual has to step in. and uh, you can read all about it.

Oh no, I should have, uh, read the specs of this thing better. It looks like the 6047 that I've got is only a 7 and 1/2 digit resolution. It's not the 8 and a half digit which is the 6048. There you go.

Ah so I'm not officially a volt nut here. I was thinking that I'd got an an 8 and2 digit meter. but I don't think I have bummer. W they're really big on math.

Look at this. These are all the functions built in. uh, ratio, power, polom, uh, what are we? Nonlinear function got logarithms, square roots, tangents Arc tangents, all sorts of fantastic stuff. variance, standard deviation, all that sort of stuff built in.

Terrific. And there you go. If you want to calibrate the thing, there's a calibration uh button on the switch on the back which you got to uh set first and you enter Program 99. Now I can see that that cow sticker is still in place on mine on the switch on the back panel.

So presumably nobody's tried to fiddle with this thing. And for those who want to know the specs here, you go the 6047. Look at that. this is uh, 24hour.

uh, drift specs. look 011, PPM or half a PPM there for the 6048. Oh killer accuracy. 90day accuracy.

You know, even at this one. see, the 6047 isn't a huge amount better than the 6048, for example. Look, it's you know, bugger like one digit in it there4 instead of3. Not a huge difference there between the two.

And as I said, right at the start, the onee, uh, nominal accuracy 07 uh percent there. So yeah, that is like an order of magnitude better than my Um Agilant 34 61a, 6 1/2 digit meter. And even the 1ear specs on the resistance here pretty impressive. goes down to as low as 9% there for onee accuracy.

There you go the ADC uh multiple ramp. They've got a patent on this thing German patent. anyway. you can go look that one up if you want I mean you know old hat these days, but eh, back in the day would have been a big deal and yeah, it's just an integrator.

That's pretty much what it is now as always. I'll link in down below to the EV Blog.com website for the highres tear down photos of this thing plus the Uh schematics as well. and this is the 6048 schematic. Uh, so that's the higher end model and that's the 6047, so check the difference.

There we go. I Can see we've got some extra circuitry up here as starters. What else have we got? Oh yeah, there's quite quite significant differences happening down around here and this is the 6048. This is, uh, some of the additional circuitry obviously to power the uh, better reference the LTZ 1000 as you get.

uh, same one you get in the classic HP uh, 3458a and once again would have been individually hand selected. and if we flip over to the 80 um, uh, the 47 that we've got here, where there we go, the LM 399 even though what what they got installed is an LM 299 but basically the same thing. Oh lovely Reay sound beautiful anyway I hope you enjoyed that uh tear down of this uh, rather unusual Prema 6047 integrating digital multimeter bit embarrassed I thought it was 8 and 1/2 digit. This is when you're rushing and buy stuff just randomly you know you don't do your research probably I thought it was an 8 and 1 half digit meter and I thought that the specs were the only difference between the two, but eh, it's 7 and half digits anyway.

I Got to do some more work on this sucker and um, see if it is within Speck It just may need some warmup time or something like that anyway. Needs a fair bit more playing around. but yeah, rather unusual beast from the late 80s. Hope you enjoyed it.

And as always, if you want to discuss it, E Blog forum is the place to do it. Catch you next time.