Hi welcome to Tear down Tuesday before we get into it. Just wanted to let you know about a video that uh was shot of me talking at the Ignite Sydney conference the other week and if you want to see it, click here. You'll be able to jump to that. It's a 5 minute lightning.

Talk about how I make a full-time living on YouTube Yes, you can watch me make a full out of myself live on stage in front of 500 people. Beauty! So what we got today: Something incredibly simple: A Gen Red Decade Resistance Box that I scored from the auction I've got two of these as you saw in previous videos or you should have seen how interesting is a box with a bunch of precision resistors and switches? We'll find out. Switch Pornography I Think let's go and here it is: the Genrad 1433 F Decade Resistance Box 110 K uh total 10 milliohms resolution. There's the decimal point there and it can go down to 10 milliohms and uh, you've seen a previous Uh video on the Um IET Decade Resistance Box This box.

this is about $500 uh, Class One and of course, Genrad now owned by I so the same company, you can still buy this model Deca Resistance Box: It still looks, it looks a little bit different, but it's um I I'm assuming it's uh, pretty much precisely the same technology inside. this one's quite old, not sure of the exact uh date, and uh, of course you've got my homemade uh resistance uh box here, which you've seen in a uh in a few previous videos and it contains uh, various Precision resistors in it. Well, two Precision resistors. They're about $20 each from Digi key and they're .01% class.

same as this uh one here. this one's actually 05% So this 10K resistor I've got in here is technically uh, you know it's like 2 PPM um class. this is like 5 PPM class. So technically my $20 resistor in here is better than this Decay resistance box.

which if you want to know the price, if you, well, if you have to ask the price, you can't afford it. Really? um, we're talking in the uh, many thousands of dollars here if one of these Decay resistance boxes. So uh, why, you know this has got a $20 resistor in it? Uh, it's a little bit better than this, but the trick is getting the contact resistance right in these switches. These just aren't going to be ordinary switches inside here and we're going to see that in the tear down.

So I expect some switch pornography inside this thing. We'll find out, so let's crack it open. Oh, and by the way, this was supposed to be unserviceable as you saw in the previous video. it's slightly out of Tolerance I showed the spec sheet uh, last time.

So I expect uh, just to need some contact. You know, clean some of the contacts in there perhaps? and uh, she should be right to go. so maybe we'll do that after the tear down. we take a look at the binding post here and there's a actually a bit of corrosion on these here and uh, well, not surprising considering its age Now, these aren't just regular binding posts, these are actually uh, torium copper binding posts to give you a low um EMF which I've talked about in uh, uh, previous videos you know, thermal EMF effects and uh, stuff like that and of of course, um, they're uh, isolated from the shazis so the individual resistors there you can see them isolated and we've got ourselves a shielding uh Ground Terminal as well for the case in case you really want to uh Shield out that noise.

So um, yeah, these are, uh, probably you know I'd like to replace them, but I physically I don't think it's possible I think inside, we'll probably see that it's probably not going to be uh, uh, easy to do that. and really, you know these are top quality. Um, just clean them up a bit and uh, they should be uh, good as gold no pun intended and bit of a macro shot there for you. uh.

binding post effici. andado. So yeah, we do have the hole down the bottom down there so we can use this as a four wire. uh, terminal measurement of course.

Plug your banana plug in the top and then have your sense wire uh, coming out the side Of course you have to really do that when you're talking about 10 milliohms resolution. here. with with, you know, a Precision uh calibration standard Metrology Grade box that we've got here. All right, let's crack it open.

We've got uh, looks like three screws here. There's not another one down here, but there's interestingly, there's a cover plate down here which looks like it comes off separate and it's right under the binding post. So I I some sort of access they've designed in Tada There we go. They designed in some sort of access to the Um front panel, uh, terminal blocks.

Not sure why. maybe that's part of the Um I don't know, uh. calibration Factory calibration of these things or something. Have no idea.

actually. on second thought, I think what might be going on here. This is for the user. Perhaps if you got this thing, maybe perhaps, uh, mounted in a rack or a system or something, you can, um, access the terminals on the back and you can wire it into a system.

perhaps? Um, that's I don't know. that's I Reckon that's a reasonable guess anyway. and I expect to see some massive switches. These things won't be just your, uh dicksmith.

PCB Mount cheapies. Let me tell you, there'll be a bit of Technology I'm sure which goes into a Metrology grade switch now. Oh oh oh, the whole thing. LTS Off here we go.

You're ready. Tada How interesting is a box with some resistors in it? Oh look at that folks. Beautiful! Hey what's going on here? This one looks different to all the others and this is inter it. Look, we don't have I expected these type of axial Precision resistors.

They're uh, like I don't know. Ah, they're a vishe uh brand one. So I sort of expected that, but they're the only type used there. The rest look like wire wound resistors.

Look at that. Wow. Like as in you know, all separately wired and then down on the low order. Yeah, these are the low order switches down here.

These are the uh Point these are the 100 milliohm and that's a 10 milliohm. We've got little I'll show these in great. uh I'll show these with the macro lens on. Zoomed in of course in a minute but uh yeah, there you go.

That's inside a Metrology grade decade resistance standard. Beautiful. The wireing. It looks like we have um, silver, um plated wiring perhaps? Yeah, it looks like yeah, silverplated wiring and uh woo.

Spared no expense and the contacts of course will all be uh, silver plated as well. And yep, I just looked up the uh manual for this thing and it boasts a um silver alloy. uh, contacts all throughout this thing to maintain. Uh, less than 1 million per decade total per decade? Brilliant.

And of course we've got uh uh, seven decades here. So uh, that's less than if with 1 million per decade, that's less than the uh, least significant, uh, bit of the lower decade here. So, and I'm sure they achieve better than that in practice. That would be like a worst case figure.

So beautiful. But um, why is this one different? This is a switch manufactured by Quadtech. There's the part number um 0510 97051 I'll have to look that up individually. serial numbered.

Um, it's almost as if that is like they they've repaired this thing or something and they've replaced that. I Mean there's no reason why this is the Um one. This is the one. K uh yes, that's the 1K um, uh, decade There Why that one needs to be a different type of switch to all the others is is absolutely baffling.

So I I Suspect that this has been probably repaired. Um, the good news is is that I got two of these so I can crack the other one open I might do that very quickly now just to confirm that it looks like I reckon that this one's been repaired. Okay, he here's the other one. It's cracking open and yep Tada Oh Tada But look at the Uh contacts down here.

they have replaced, they have replaced well. These ones don't have the uh silver contacts on them. These ones have uh like just bare copper contacts on them. Bizarre.

I mean the end one here is Silver the end contact there and over there is silver of course to when you switch out that decade, but they've decided that they're going to lower the cost. I Guess on these two upper order switches, the 1K and the uh 10K decades by not going with the silver contacts on there the silver alloy contacts because you don't uh, need them when you're up in that sort of uh range I guess they? they've determined that so that's interesting, whereas the other box has still the silver alloy contacts right up on the 100K range. So man, that is, uh, there. There certainly, uh, differences between these two units.

So here's one individual decade switch up close here. check out the multiple contacts on there. What's that? Four individual uh contact pads coming out from there all the way into that switch mechanism. There's a ball here of course, which if I rotate that here we go.

Oh, they're a bit stiff. Oh, really stiff these things. especially when I'm not getting the right angle on there. Oh, that's horrible.

I'll give you some switching. uh, money shots later. But yeah, they've got the multiple Leaf contacts on that thing which is uh AB Absolutely fascinating. And these are self uh, cleaning contacts.

or they're advertised as self cleaning contacts. and man, that's just beautiful. It really is thing of beauty and a joy forever. That's why these things cost in the thousands of dollars.

They don't high volume manufacture these or lots of silver goes into this. these are they wouldn't be. um, silver. Like solid silver.

Wise, they're like a silver. You know, as they say, a silver alloy. Um, so you know either. Silver Plate heavy silver plating or something like that? Not entirely sure, but it is some form of alloy.

And here's a closeup of that wiping action with all five sorry, four, uh. contacts there. Absolutely beautiful. Oh, look at that.

you see that there's actually appears to be quite a bit of Gunk inside those contacts. There, you can see it all. just, uh, sort of wiped off on the right hand side of that contact. So maybe that's what's uh, you know, this is the Uh 10.

This is a 100 milliohm range switch. So, but you know these things. If they've been sitting in storage for quite some time, you really do need to, um, operate them. Uh, you know, quite a few times before they will, uh, meet their minimum contact resistance.

uh, spec again. So yeah, um I clean these things until I actually do some measurements on them and see if they do actually need to, uh, be tweaked or not. And for you ball bearing afficionados, here we go look at that. Oh yeah, could play with this puppy all day long.

They really haven't mucked around on those solder joints either. They've uh, crimped those over and then really solded them in place. They didn't bother cleaning up the joints there. I Guess they decided they didn't have to.

So yeah, you know it looks a little bit ugly, but oh, super reliable. You can bet your bottom dollar on it. And there's that uh wire as well. I Mean it's a huge diameter, absolutely massive diameter.

and uh, so that's some sort of silver alloy. uh, contact and I silver alloy. Uh, contact in here and I'm assuming, uh, the same silver alloy uh, wire in as well Because when you're building these things, you know you want this wire. Um, you know this is a Metrology grade bit of Kit So you really want this, uh wire here to be the same material as um, as your contacts and uh, everything else.

And as you're wiping, uh, you know, contacts over here. So so your actual contact, pad your wipes here, you wiring all that you would want that to be the same. Uh, so it's got the same uh, Tempco and uh, you know, thermal effects and there your two, uh, input Jacks there and as I suspected, they, uh, won't be terribly easy to actually. uh, replace those I wouldn't uh, dare touch them really? um, probably just, uh, leave them in place like that.

Now one of the most, uh, surprising things I found in this is not the switch contacts there, you know, over engineered to the hill, exactly what I expected. but uh, the Precision resistors in here. look they're individually wound like these and these would have all been um, well, either you know, hand or machine Assemble But they definitely hand tweaked at the end of it. You can tell by the little Blobs of solder in there and there's some uh, better ones which will actually shot.

This is a very, uh, clean one. This is the uh 10K So each one of those is uh 10K um, that's a 10K resistor. So they got a high, very high resistance uh wire in there and um, they're You know, this wire cost a fortune. These things.

You know, they don't just buy an off the-shelf resistor. These are all, um, handmade. You know, hand wound, hand assembled. Absolutely incredible.

So let's take a look at the one of the ones that's been, uh, tweaked. I Don't know how many um, individual wires they've actually got in there. I Don't know anyone want to get in there and count? There you go. You could be counting that until the cows come home, folks.

look at that. Hundreds of turns, probably finer than a human hair. Look at that. Now you can see what looks like, um, some sort of, you know, oil or liquid on there.

It's not. It's actually a conformal coding. They've done that to actually, uh, protect. These wires, have actually, uh, probably dipped the whole thing after it was, uh, wound.

They probably you know, dipped a lot of it or coated it or brushed it or something like that in an individual process and then then they would have had all matching silver alloy wire to wire those into the switch contacts and the switch and those posts in there. They'd be the same, um, silver, um alloy wire as well. Now here's the same winding for the Uh 1 Ohm version and look, it looks incredibly messy. but someone's gone in there and hand tweaked all you know, hand solded and hand tweaked the values in each one of these.

Precision 1 Ohm resistors. Unbelievable. And the 10 milliohm decade really easy. They've just gone well.

It's exactly that length of resistance wire there, so you know we don't have to do anything fancy like we do. And look at the 100 milliohm ones, they not actually haven't actually used a wire there. they've actually used a flat, uh, resistive, uh, strip. I You know I'm not even sure what.

uh, that material. You know, some sort of nichrome or something. perhaps? um, some sort of, uh, resistance. Uh, you know that you typically find in a resistance wire or something like that.

It's obviously not just you know. regular, uh, straight copper and it looks looks like it's almost been heated up there on the end. It's a different color to say this one over here. so I you know I think each one of these I think is possibly, uh, you know, individually tweaked to be within spec.

H So that's the 1 Ohm decade down in there. You can see it is really quite a mess and then we get up into the uh uh 10 ohm one here and uh oh man and it's uh, you know it it, it looks absolutely awful. but uh, you know these things are Metrology grade. They're individually tweet to get the absolute best performance and that's why they cost thousands of dollars.

You can't Mass produce these things like you would think something like that you know you'd expect to see come out of some, you know, hamshack done with a plumbers? uh soldering iron I mean in it does not instill a lot of confidence at all, but it works Metrology grade Now this is the Uh Quadtech switch we we've had bodged inside this which looks like a uh you know an after uh repair I don't think it was done at the Uh Factory and if we take a look at uh some of the resistors they're are Vish uh VT s is that it come on focus and the resistors here are a vishe uh 1K these are the 1K ones um 1K 0000 exactly like it uh says on the one in my resistance box but there a uh well that is that a date code 89813 not sure um but it's a VT As2 I'm assuming that's the model number I'll have to look it up and now we want the Tolerance on this thing. it's on the other side and there it Isow 8% so not. You know these individual resistors aren't uh, quite well. Actually, they're better.

Not quite as good as the 10K one I've got in my box. The one I've got in my box that I paid like 20 bucks for is U .01 for the 1K I've got 005 for the 10K but uh, going to see if I can find a data sheet for these things. Oops, I read that. Uh, slightly wrong.

It's actually the VTA 52 series, but check out the vet. uh, foil. These are foil resistors Precision foil resistors. but check out this uh website.

I'll link it below. What? I love about this. We'll get into the data sheet, but look at all of the application notes that they've got here. Oh one after my own heart.

Seismic seismic instruments for oil exploration and need Precision resistors in the analog circuits? They certainly do I've used many of them over the years cuz I Used to work in the seismic industry, but look at all these. uh fact sheet SL um application uh notes understanding the risk of uh ESD selecting resistors for preamp amplifier uh The Invention and evolution of the world's most precise resistor. Oh man, got to read that and uh Precision centers was for small prototype runs. They got a whole swag of um, interesting little facto ultra high Precision resistors to be used for secondary standards.

Ah, obsolescence, counterfeiting. Oo there you go. How to select resistors for precision applications H Oh, transmission data transmission problems BL bulk foil resistors introducing new blah temperature coefficient all sorts of stuff component selection, layout strategy for for avoiding thermal EMF noise Wow, this is a little gold mine here folks. Definitely check out this link and uh, have a look at these things.

There could be some really interesting stuff in here and here we go. They bulk metal foil technology as all of these Precision resistors are really we're talking 8 PPM Uh well 4 PPM uh Class over uh a limited temperature range from 0 to 60 Load life stability 25% you know, not too dissimilar to my one, which is where is it? Here it is. My ones are V as well 05% load Life 2 PPM Um, you know these are the $20 ones from Uh Digi Key and uh, very nice. And if we take a look, here's how they like trimming.

Conceptual illustration: There you go. That's how they interloop capacitance, reduction in series, current path before trimming and then current path after trimming. They'll trim off some of this larger trimming process, removes this material from short in strip area, changing the current path and increas in resistance, so they just get the laser in there and burn that out. Beautiful! That's why these things are very expensive and they can cost 20 bucks for one resistor.

Not a problem and this is going to be fascinating. Reading the invention and evolution of the world's most precise resistor. The legacy of Dr Felix Zandman Who knew Dr Zelix Fan: Zandman is the man. He's the founder of Vishe Inter Technology.

Oh, didn't know it was Vishe into technology. Oh, sadly, he died on June 4th 2011 at age 84. A What a bummer! There you go. 1962 to 72.

Beautiful all the history. Definitely worth reading folks I Love it. Who knew all this stuff was here? I Had no idea. just buried away on you know the pay.

Well buried away in the Vishe Uh website for these particular resistors. I'm sure it's linked into the other resistors as well, but can't say I've ever. uh, come across this before. Facts at a glance I guess that's what vishe call their application.

uh notes. Neat. But here we go: Component selection, layout strategies for avoiding thermal EMF noise and I've done a tutorial on this of course, the thermocouple tutorial and bingo, there you go. Cold Junction Hot Junction Alloy Loop resistance all that, uh, thermal Junction stuff which matters.

Design considerations host of materials Alloys and uh well, if you want to know about uh, low, uh noise, low thermal uh EMF noise designs and uh W look at that bulk. There we go. There's some differences between metal strip type, bulk metal foil which are the Precision ones that we've got in here and I've got in my box and they're using practically any ones. And then you got your thick film resistors and metal strip types.

Ah, great data in here. folks. Have a read and that Quadtech switch. Well, they, well, formerly Quadtech.

There they are. They're now Chroma Systems, Electrical and Medical Device Testing, Instrumentation and system. So yeah, I Don't know if they uh, actually make switches anymore. probably not.

But they make high Po and safety testers LCR meters. Who the hell knew? Meg meters and Milom meters and medical systems. Do you believe it? And then they've got power products as well. They do DC Electronic loads.

Who knew digital? M What they do. digital multimeters must be a rebadge, surely. Digital power meters? Ah no. I'm doubting that they'd actually do anything themselves.

Well, not some of those anyway. So that sucker there may not actually be a Quadtech switch after all. they may have sourced it from uh, Quadtech. but yeah, it could be someone else.

So if anyone actually knows, then, uh, please post it in the comments. All right, let's measure this thing. I've got four wire, uh terminal set up here. of course.

there we go. I've got the leads going over here and then the voltage sense coming back into here. So we're in four wire mode, which is the uh best way to measure this and we're getting seven odd milliohms there. I mean I can go down to 10 microohms resolution on this thing, but really, we're down in the noise.

I've got it all set to uh zero. Let's see if it's repeatable. it should. oops.

got it back to front. it's upside down. all the electrons are going to fall out. This one here is H the 10 milliohm one and there we go.

It jumped up by pretty much bang on 10 milliohms and it goes back. not a problem. So if I give them all a little tweak there and uh, bring them all back then we should be reading. yeah, it's still roundabout.

yeah Point uh, triple7 or 7 7, 8 milliohms or thereabouts. So there you go. we can bump that up by one and we can go up to all the way up to 10 10 Point there we go. 10.7 10 that 10.8 um sorry 100, you know 108 uh and can bump that up by one we 0.1 ohms beautiful.

it's it's bang on I mean you could oh man to actually get a proper calibration Metrology measurement on this thing. When you send in for calibration, you got to tweak and dick around. probably have to turn some average in on I haven't got any average in on here and uh, stuff like that and you know you really have to, uh, get it. um, quite precise to make this thing work, but you know I mean this is It's bang on.

You know it's as good as I can probably measure with my gear here I could muck around a little bit more, but you know, as we saw on those calibration reports, this thing was out by like you know, a you know, a couple of Milli Ohms or something over spec or 10 moms over spec or something crazy. This thing is uh, bang on that's uh, that's 1 Ohm there it is and we can go up to 10 ohms and we still get that um you know? Well we jumped up to 9 milliohms uh offset now. but geez, you know I mean we? it's You know it's well within, it's it's within spec I think not a problem whatsoever. 100 Ohms is actually a little bit.

uh High what is that in percentage I mean that's only like uh, you know, 0.01% so you know. still very, very close to uh in Spec I'd have to get out the full spec and adjust for you know uh AG in and all sorts of uh stuff. but that's the uh 1K with those uh Precision uh those Precision metal uh foil ones so it's just you know, it's just oh sorry, no that one's not. That's the for that's the 100 ohm this is the 1K There we go.

look at that beautiful well within spec I think 10K look at that I mean to give you an idea how bang on that is folks .01% Okay which is pretty much the the Uh accuracy, the basic accuracy of this box. it's you know it's a .01% class uh decade box pretty much .01% 10K that we've got there of those 10 resistors in series okay is 1 Ohm like that? That digit there is .1 0.01% So this next digit over is .01% crazy. So look at that. it's settling down now and we're talking almost one% on that that that last digit.

There we go. It's just. you know I mean I This is ridiculous. You know you can tweak and measure and measure the drift on this.

You know we're down in the drift of the noise. Almost. It's just it's just ridiculous. But there it is.

And these resistors as you saw were 8% uh, marked. So 8% of 10K we're talking. You know it should be like 80 here, right? It's this digit right here is uh, you? your point? It should be 80 and basically 80 on that display there. uh8 ohms uh is 8% and look at that, it's well within that.

it's practically bang on. And of course, then you got to take into account the accuracy of this thing. and then you get into the whole Metrology thing and you know it's just. it just gets absolutely insane folks.

But you basically can't get any better than that. Quick I should take a photo that it's bang on 10K and on the 10K Here we're talking uh .2% Um, you know, well within the specification of this unit, not a problem whatsoever. Look at that. There you go.

I didn't show a closeup of the uh other box with those uh, what look like uh, copper contacts on the top with the one silver uh alloy contact. at this end, you can see like the uh grease on there. You see all the grease marks on this. It's uh, certainly hasn't lost its grease that's for sure.

So I'm going to have to spend some more time on these boxes and uh, measure the Uh individual ranges and stuff more closely. and uh, compare them with the spec and things like that and take into account my um HP uh, 3457a accuracy and you know all that sort of stuff. and uh, but I don't think I have to clean the contacts um on this, but uh, you know, really? I shouldn't need to just wipe them a few times cuz these things have been in stores for quite some time I think cuz they do have a stores sticker on it. There it is stores.

Tada So you know they've been lying I think they've been lying in the uh store room at the uh military uh base for uh, you know, quite some time and they just need to be operated five or 10 times. and I I think uh, we find that if we did that, you send them back for a proper, uh, proper calibration. Uh, check. That'd probably be uh, bang on.

But if you did want to clean these yourselves yourself, um, all you need is some WD40 and I Know what people are going to say? don't you dare spray that magnificent box with that crude WD40 Well folks, it's actually the recommended or one of the recommended. You know though, people will be screaming oh you got to use deoxit and stuff. Well if you have a look at the advice here should switch contact. cleaning or lubrication be required as may be indicated by an increase in zero resistance.

This may be done by spraying to switch contacts with a conditioning compound such as WD40 good WD40 oh yes, dioxite from uh K Laboratories or which um I've heard of but that's like $25 a bottle at JC car. so you might as well just use uh the uh the the deoxit gold stuff. like 25 bucks a bottle got to be kidding me. J car are ripping off there I don't know what price it is in the US but um WD 40 That's the recommended thing from this is the you know this is the actual maintenance uh thing from I labs for the 1433.

They actually tell you to spray it with WD40 or Super Lube with Ptfa I haven't heard of that Super Lube uh stuff. but there you go. You can actually spray this sucker with uh WD40 not a problem and of course you got to have the genuine made in Australia stuff. Beauty So I'm actually pretty darn uh happy with this box.

So uh I You know once I check them out I'm going to keep one I'll probably I don't need two of them. uh, flog one on eBay or something and look, it's actually uh, this one's drifted uh, slightly down. You know it's probably not the D box drif in. it could be my meter.

It could be a combination of both or whatever and uh. but if I turn that down, we'll probably see that least significant digit. Oh oh yeah, don't don't touch the wires. Don't touch the sense wires who look at.

that goes down to 9. Okay, it basically keeps that least sign that last, uh, least significant digit? almost. It's pretty impressive. Very impressive box.

I Really like it. Oh there we go. Bang on no, it went up a little bit. Bang on to 6K there five.

Oh look at that. A folks pornographic really is. love it when a plan comes together. 2K Oh oh, we've increased a digit resolution there on our meter because, uh, our meter.

uh, just jumped up. You'll know that's the ranging there. So we just gained ourselves an extra uh, extra digit there. So here it is.

there we go. and so we're getting what looks like a large count. but it's the same as before. Ah, beautiful really is I Love it.

Look at that spot on anyway I hope you enjoyed that. That's uh, it's not just a box. Well, it is a box with some switches and resistors. but they're pretty interesting resistors and they're pretty interesting switches.

I'm sure you'll agree. and if you've got any, uh, more info on the exact alloy types and uh, things like that, then please, uh, leave it in the comments or jump on over to the EV blog. Forum that's the place to discuss it and if you like tear down Tuesday please give it a big thumbs up. Catch you next time! Um,.