Hello and welcome back to a new video about the Klemt Echolette NG-51 S. Today we want to talk about the power supply of the device. What do I mean by that? Basically everything you see in this picture. This is an excerpt from a very old schematics and I chose this one, because here all the components that I want to talk about are drawn very close together so that we always have them in the picture with one look. I'll be coming back to this schematics again and again throughout this video to show which parts we're specifically talking about as we go along. So, what is this video about? It's specifically about the mains connection of the device, because it usually starts with the mains cable. Then there's the transformer, the so-called voltage selector switch, the frontpanel switchboard illumination, the tube heater and the de-hummer - these two topics are very closely related, but I've divided them into two sections - and finally we will talk about the rectification in the device. Well, let's start with the mains connection. What do i refer to? I'm talking about those parts marked yellow here and about that weird looking cable. This is not so well known today, but it was actually the predecessor of today's IEC C13 plug ("cold device plug"), which means that there was something like that on many devices: from vacuum cleaners to echo devices. And this odd looking cable came as a ready made cable, but you could also get this as a kit to attach a spare cable or your own cable of the desired length. 'The predecessor of today's cold device plug' actually says that this cable no longer exists in this form, at least not completely new or as a series cable, and that's why it's naturally become a bit rare. So if you cleared out an apartment in the 70s and maybe the early 80s or cleared out your grandfather's attic, then there was a very good chance that you would see a whole box of them somewhere lying around - just like we collect our cold device cables today somewhere. But today it has become rare and therefore - as is so often the case on the market: great demand, great prices. Let's look at a few examples. Here we have an example from Ebay for 39 Euros. This is marked "Brand New" and looks very new, too. So here is a very nice new plug and also a clean cable. It's one of those with a fabric cover, it has a bit of a retro look and the plug we just saw and 39 Euros plus 5 Euros shipping costs. Well, and you can already tell that the seller knows exactly who his target audience is, because a certain name dropping takes place here: Neumann, Dynacord, Klemt Echolette. So names that definitely ring a bell, you have to include them in the description of the offer, because otherwise everyone will ask themselves: "Is it April 1st already?". Yes, next one it is a little bit cheaper. We have a used version here for 29 Euros, but the shipping costs are a bit higher. But here too: the name dropping is there, even if the name is spelled wrong ("Klemmt" instead of "Klemt"). But Neumann, Echolette, Echocord, Dynacord and here the various devices by Klemt are also in the description. And then there are always fortune hunters who also have problems with the correct spelling of the name, but have no problems charging almost 80 Euros for such an old cable and additionally also have the cheek to charge additional 5 Euros shipping costs. Here we are in the price area of ​​parcels at DHL, which can weigh up to two kilos. So I find everything very questionable, but of course there is still one or the other guy who still has to top it. And I would like to show you this nice offer for a whopping 299 Euros. And so that the costs of the seller are covered, of course, almost five Euros additional shipping costs. And what are we paying this price for? So we have this said mains cable here, then we have a short mono jack cable here, patch cable. Here it looks like an XLR cable, maybe 3 or 5 meters length. And here again a stereo jack cable with a socket on the other side. And here is an old mono jack cable. Yes, and what that is, we don't know exactly. But charging 300 Euros for these five dingy old cables already suggests that one or the other has the expectation that someone is stupid enough to pay these prices. Yes, I don't want to hide the fact that there are of course still reasonably viable solutions on the Internet. Here, for example, that's one of the cheapest prices I've found: 22 Euros. However, these are also old cables that have been tied to knots quite neatly here. So, everyone has to decide for themselves whether they actually want to spend that much on a pure mains connection cable. Especially for this kind of power cord! Because there are definitely reasons why this is no longer used on new devices. One of these reasons is, for example, that you could touch live parts - not normally, but the protective earth conductor is electrically a completely normal conductor that is designed so that it can carry voltage, namely in the event of a fault. In the event of a fault, a lethal current can be diverted to earth through the PE connector and if you want to pull the plug in this error case, you can get a good smack here. And that's why we have completely different plugs today, where the protective earth conductor is no longer open on the outside. Well and that's why, given the price situation and because this whole construction is not entirely harmless in certain cases, one should consider whether a conversion should be considered. Namely a conversion to this IEC C13 socket, I always say it's the "computer socket", because it's found in every computer power supply. And as you can see from this example picture, it also fits perfectly into the device. And that, of course, enables us to use ordinary cables that everyone has in abundance at home. Well, let's look again at a small drawing to see exactly how this mains wiring is laid out in the device. So we have our mains connection socket here and one side goes to the on/off switch. From there it goes to one foot of the fuse holder and after the fuse it goes to one winding end of the transformer. And on the other side it goes to the other winding end of the transformer. Here we still have as a speciality that this green-Black wire is not designed as a continuous cable, but is actually soldered to pin 7 or connection 7 of the voltage selector switch and it is really two wires. But in principle a completely normal circuit that can be opened and closed from two sides: Firstly by the switch and it can also be interrupted by the fuse in the event that too much current flows through here. One thing I might have to mention here speaking of the wiring in detail: I have a limited number of NG-51, but it's a handful. And if you take a look, the wire colors are not always exactly identical. I have one, for example, where, as shown, that one wire is red-black and the other is green-black. Here in this device it is actually a green-black wire and an all-black wire. Yes, you don't know whether it was already like that from the factory or whether someone may have replaced it over the course of the 60-year history of this device. Can't be known, so don't be surprised if the wire colors in your devices differ in one place or another. I think that's perfectly normal. There is also one small thing to note about the mains switch: this model left is very often found in very old devices and this model right is more likely to be found in the later NG-51 S switches. So both are absolutely fine and fulfill the same function. Next, let's take a look at the transformer, as I've highlighted in yellow here. If we take a look at the transformer from the outside, then we see a designation on many versions "BV 1260P", but it doesn't necessarily have to be on it. I also have an example here that looks completely different. However, this is an example from the Internet and I think this device was sold somewhere in California. Well, it looks a bit different than the first one, but "BV 1260P" can also be found written on the schematics and we also have a hint on the manufacturer here: A circle that contains a kind of sine wave and at the same time it also looks like a "M". The manufacturer with this logo is the company "MAHOC" from Munich (same city where all Klemt devces came from) and there we see the transformer again as a whole. And it's like a structural component, on the right side it's attached to the rest of the chassis and on the left side there's a complete panel attached that holds the mains socket, fuse and voltage selector. That's why it's a supporting structural element of the whole device Yes, I don't want to say too much about the structure and functioning of transformers in general, just enough to better understand the following slides. So a transformer works very simply put like this: We have a primary winding of enameled copper wire through which a primary current flows and on the other side we have a secondary winding through which a secondary current then flows. And the whole thing is applied to an iron core. And when a current flows through the primary winding, a magnetic field is created around the wire, resulting in a magnetic flux within that iron core. And this magnetic flux again induces a voltage in the secondary winding. This is the simplest explanation of how such a transformer can work. I don't want to get into the math, but here are two simple formulas for an ideal transformer. "Ideal transformer" means that there is also an "unideal" transformer. That's basically the issue, that these calculations and what we're seeing here don't work quite as smoothly in reality. There are various reasons for losses, i.e. where our current that goes in here does not produce what it could in the secondary side, but on the way there certain things are simply lost and the transformer specialists have of course included these losses in correspondingly more complicated equations. And now let's look at the very simple equation just to keep it in mind for a very ideal transformer. So let's take a quick look at these two equations and see how they help us to understand what's to come. So, for example, we see something here in this first equation that we actually already know: If you want to increase the voltage on the secondary side, then there are two options. So either you increase the voltage on the primary side or you change the winding ratio here, i.e. the number of windings or how many windings each of these sides have. Because the number of windings on the secondary side is in the numerator and the number of windings on the primary side is in the denominator and that means the more windings the secondary side has, the higher the secondary voltage will be, because the fraction will always be larger, the higher the number up here in the numerator is. That's quite logical now, we already know that. In order to step up a voltage we need to have more windings on the secondary side. So and with current, it's the other way around in a way. We can see that the fraction has been swapped here, we now have the number of windings on the primary side in the nominator. Well, let's take one lesson out of this: If we get into a situation where the amount of windings on the primary side is reduced, then we can only compensate by increasing the current on the primary side. This is an insight that we will need later to understand a few things. So, if it is true that the windings on the primary are decreasing in any way and we still want the same current on the secondary, then we need to see that we increase the current on the primary to keep this equation working. I don't want to say more about it now, that's it with the mathematics. Let's now take a look at how the tranny is built in the actual NG-51 and also at these losses that I mentioned. So, talking about the losses: You have just seen on the diagram: There is an iron core on which these windings are applied, but in reality it is not a "monoblock" in this device, so to speak, but the iron core is designed as a large number of stacked metal sheets that are stacked on top of each other and they are also pressed tightly together by bolts and screws. And these individual sheets are insulated from one another, which means they have a coating of insulating paint that ensures that they are not electrically conductive throughout the whole block. Yes, and there are reasons for that. Here we see the iron core again. One of the losses that I'd like to mention and that can occur in reality compared to an ideal transformer are the so-called eddy currents. Yes, where are the eddy currents hiding here in this left picture? This magnetic flux would cause an electric current to flow in a 90 degrees angle to it, induced by this magnetic flux in the iron core itself. This is called an "eddy current". And this eddy currents drain energy from the magnetic flux, which means that all the magnetic flux that is generated here cannot induce a hundred percent secondary voltage over there. Because part of it is lost because eddy currents can flow here. Yes, and that's why this transformer core was designed here as individual laminated sheets, because this greatly reduces these eddy currents. Yes, you can see that here in the drawing, which aims to illustrate this a little bit. Of course, certain eddy currents still flow _within_ each laminated sheet, but the overall loss factor is significantly lower than if it were actually implemented in the form of a single large iron block. Yes, that's why it's always very important that these laminated metal sheets are actually isolated from each other. So completely rusted transformers, where this insulation is no longer given, can cause significant losses and then the device may no longer work within the parameters in which it should work. Yes, that should be all about these aspects of a transformer in the scope of this video. This is a science in itself and if you want to read more about it, you could refer to these three Wikipedia articles as a starting point. Let's summarize a few things about the NG-51's transformer that I deem very important: As you can also see on the schematics, we have four individual windings on the primary side and we have two taps on windings on the primary side. There is a tap here, I'll call it the "winding 130", and another tap down here - this is the power supply for the motor shown in the last video. So two taps, one here and this winding is also tapped for the motor supply. The designations that you can read here on the schematics are sometimes a bit confusing or misleading. I'll say a little bit more about that later. Yes, and on the secondary side we have two windings: This one, one with 6.3 volts and one with 275 volts. And what is often overlooked, we also have a shielding winding, which is right here in the middle. It's already indicated by this ground symbol here, because the shield winding is connected to ground on one side and that's this nondescript cable here, which ends in a screw that has ground contact. What we need that for, I'll say one more about it later. Let's take a look at the two sides of the transformer again in real pictures, I've unraveled the cables here so that we can follow everything nicely. This is how it looks here, again the note: These two wires, they both look yellow. Both are shown in yellow in the following illustrations. But the fact is that in many devices this one right is more orange, which means I don't know whether orange is really the norm or whether the device I used for display here has them actually both yellow. Or whether this yellow here was simply orange once and has faded with time. I couldn't really tell. I have perceived both here as yellow, just consider that this connection in your device may have an orange wire. Yes, you can see it here now, it's another device I own, it clearly looks orange here. And this to the left definitely looks yellow. So you can tell the difference very well in this other device. What I want to do now so that we don't just have to talk about the wire colors: I've now simply numbered these eight connection terminals on the primary side from left to right. I will also stick to this numbering in the following slides, so please keep that in mind. From 1 to 8, left to right. I've already said it, the primary side has a larger number of partial windings and what exactly that is supposed to be or how that is to be understood - well, maybe we can get closer to that by measuring these windings under voltage. And you can see that in these six pictures, I'll explain it a bit more precisely now: In the first picture I measure between connection points one and eight, I have around 42 volts there. We already know that, this is our power supply for the motor. In the second picture I measure between six and eight 115 volts. In a 220 volt power grid that would be 110 volts, but since I'm running the device at 230 volts, the voltages are a little bit higher. But that 's not important at all, so between six and eight we measure 115 volts. Third picture top right: between three and five I measure 20 volts. Then it's on to the bottom left - between 2 and 8 I measure 230 volts. These are our two mains connection points. Between three and seven, bottom center, I measure 135 volts. And in the last picture, we measure between two and four 20 volts. So now let's put that in context. So what did we measure? Between 1 and 8 we measure our motor voltage 42 volts. 1 and 8, you can see that here too in the schematics. This is exactly the tap for the motor voltage. Between six and eight I measure 115 volts. Yes, it says 110 here. That's the first thing, which is a bit misleading, in a 230 volt power grid, like here where I am, realistically it's more like 115 volts. But that's not a problem at all. Between three and five I measure 20 volts. Well, let's see - it says 130 volts here, but we actually measure 20 volts at this point. And now there is the second misunderstanding that one can have with this schematics. By no means do we have a 110 volt winding here on the right and a 130 volt winding there on the left, but realistically it is actually the case that we measure between five and seven 110 volts or 115 volts. And between three and seven we measure 130 volts, which means this small part of the winding adds another 20 volts (it drops another 20 volts). Yes, then between two and four I measured 20 volts again, which means it's in accordance with schematics time. Realistically, we don't have _one_ "20 winding" or 20 volt winding here outermost left, but this one "130" is actually exactly the same with the only difference - that this on the left is really a single winding that drops 20 volt and this partial winding is actually only tapped from this large winding between three and seven , this is our second tap here that I was talking about earlier. First tap on the primary side and here our second tap on the primary side. Yes, so much for the misunderstandings. Here we actually also have a 20 volt winding and under real conditions in today's power grids these numbers can differ slightly here anyway, because today in North America we no longer have 110 volts, but I think it's more towards 115, 120 volts and in Germany we no longer have 220 volts, but 230 volts plus/minus. Yes, and if we now draw out everything as it is wired in the device, including the cable colors, then we get this very confusing picture and all we can say is [Batman fanfare sound is played]... Exactly , but that's how it looks, even if it's confusing. The whole thing is wired into the device just like this. The secondary side is kept quite simple, we only have a few or a small subset of cables. What is that exactly? Let's break this down also. So we have yellow-red, the connections to our 275 volt winding. The two wires go to the bridge rectifier and over here we have the 6.3 volt winding, two pairs of cables go out there. One goes to the frontplate switchboard illumination, i.e. to the lamps in front and the other pair of cables goes to the filaments of the tubes, i.e. to the tube heater. And you can already see here that, logically, the lighting and the tube heating are parallel to each other. All these transformer windings don't really make any sense yet: What do we need them for? Why are there so many windings on the primary? Now if we take a look at that ominous voltage selector switch, it all suddenly makes sense But let's take a look at the whole thing visually and mechanically first. Here is a device that is found in Echolettes, but not only there, because in the 50s and 60s such voltage selector switches were also found in radios and in other devices whose sales area was not only Germany, but more or less the whole world. Yes and what do we see here? On one side we have a rotating switch with markings and different voltage indications and on the bottom we have eight connection terminals, which are also numbered in a somewhat strange way - one might think at first. So here we have 1, 2, 3, 4 and then it goes on with 5, 6, 7, 4. That means these two 4's apparently have something in common. But we don't know that yet, let's take a look at the inside first. You can take the switch apart by removing this circlip and a washer and then you can pull the whole thing apart. And what you find in the rotary button is the following: We have small springs in recesses here and such contact strips rest on these springs. They look like an "M" here. The middle post is actually seated inside the spring, so to speak, we have that present her one, two, three, four, five times and these two springs are bridged with something else, namely with this strange bridge-like strip, which just rests on it loosely . That means it's a little fiddling when re-assembling it. Well, what's all this supposed to be about now? First of all, the shoulders of this M's are these dots that we see here snapped into one of these connector terminals. Yes and there we see 1, 2, 3, 4, 5, 6, 7, 8 pieces of them. But if we count now, here we have 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12. That means four of these shoulders or contacts can not be seen here at all and that means: Yes, if only a subset of eight is connected at a time, then turning this switch obviously changes which eight of these contacts are connected to the soldering strips. This is already an indication of the whole purpose of this switch. Let's take a look at a small overview, which can be found on some Klemt schematics. I think I got this one from the circuit diagram of the Echolette E51, a successor model. But what we see here now is very important: we see that depending on the switch position, different of these contacts are connected to each other. At 110 volts, 4 and 7 are connected, 1 and 2 and also 3 and 4. And these contacts 6 and 5, they're hanging in the air, so to speak. They don't have a partner here on the other side. It's different with the 220 volt position: here it's 4 and 7 again, but then it's 2 and 3 and there we have a whole lot hanging in the air, that don't have a counterpart. This one has none, this one doesn't either, #5 doesn't either, and #6 doesn't either. At 150 volts it's different again, 6 and 5 are connected, 1 and 2, 3 and 4. That means if we remember that there is actually wires on each of these contacts or so to speak a connection wire from the transformer is soldered, then this obviously means that different windings of the transformer are in use or are actively connected, depending on how we actually turn this switch. There you can see it again, here these different colored cables from the transformer windings are all soldered somewhere on the voltage selector switch and we now know that depending on the switch position, different of these contacts are actually connected to each other. Yes, and the ominous contact 4, which exists twice, is also relatively easy to explain. It is basically the same as it is connected with a jumper wire. So four here and four there is basically the same because they are simply hardwired. And of course you can also see the connection 4 and 4 on the circuit diagram, that's the all-black line that I didn't color. Yes, what's the point now? So that different windings are obviously connected to each other when you set this voltage selector switch to different settings? Now let's take a look at concrete examples. I always have those contacts here that have a connection with a counterpart, I have marked them with a black bar and the contacts that are hanging in the air on one side are marked in gray. So that you can always see from the black bar what is actually interconnected. This is now the 220 volt setting and this is the 110 volt setting, and I would like to use these two differences between 110 and 120 volts to briefly show what this is all about. Well, we see it here too, if we switch it back and forth quickly, something is obviously moving. In principle, it is helpful if you play "current", because ultimately we have a voltage between two wires. That's the one on top up here, it comes from the mains plug or the mains socket. And it's the one far down there, which also comes from the mains socket via the on/off switch and fuse. This means that there is a voltage between this and that wire, in this case 220 volts, and wherever we have a voltage, a current would like to flow - from one side to the other. And the question now is how does the current come from up here or how can it flow from up here down there? And so it makes sense, as I said, to play "current" now. We now practically have a path here, it's like a little labyrinth that you have to follow. And when you do that, you get what I marked in red here. This is how the current can flow, namely this way over these interconnected contacts 7 and 4, then it goes down here over contact 4 into this winding and over the connection 2 and 3 it goes into the next winding and then it has arrived at the bottom. So here our current now flows through these two windings in the 220 volt position. Let's recap what we have here. So we have two windings used actively here, it might have been better to write "a double number of turns" because we have two sets of turns here that are connected in series with each other. And we have a simple current - I've called that a "simple" current only compared to what's next. So don't be surprised here, "simple current" isn't an absolute unit for anything, but to see it in comparison to what's coming next. Important: Two windings connected in series. At 110 volts we have different connection conditions here and that's why it looks a bit different. Namely, the current here has two ways through which it can flow. At first, it is almost identical, it goes over contacts 7 and 4 this way, that way. At contact 4 it goes into this winding once and via contacts 2 and 1 down there. However, the current also has a second path, which is the red one. It can also go down there via three and four through that winding. This means that at the 110 volt position, these two windings, which we already had, are connected to each other in a different way than before, so that the current no longer flows through these windings in series, but we have two windings that are parallel to each other . One here and one there, and the current flows through both separately. Of course, this means that we only have half the number of turns here, because before they were in series, now they are no longer in series. So half the number of turns the current runs through is reduced / halved. But we actually have twice the current! Hmm, why is that now? Well, let's imagine it like this: At 220 volts we connected two windings in series, these windings also have a line resistance. And from given voltage and given resistance results a fixed amount of current. That's Ohm's law, you can calculate that. However, if we now halve the input voltage and at the same time also halve the cable resistance, because they are no longer in series, they are now parallel and the current only ever flows through one of these windings. We have now halved the line resistance. Voltage halved, line resistance halved - then the current that comes out is still the same, but because this current flows twice here - namely once through there and once through there - we actually have half the number of turns in this circuit, but twice as much current. And you can see that written on the outside of many devices, it says very clearly: If you connect 110 volts, i.e. the 110 volt position, you need a fuse that can handle twice the current. I once read classified ads on Ebay and someone wrote: Well, you can switch the device between 110 and 220 volts by changing the fuse. Of course it is not meant that way, the fuse does not decide what kind of mains voltage you can use. This is exactly the other way around, namely depending on which mains voltage you use, given that the device can handle different mains voltages using a voltage selector switch, then with the 110 volt you actually have to use a fuse that is twice as strong or use a fuse that can withstand twice as much current. Exactly for this reason. Here we have half the number of turns, but because the current flows twice here, we have twice the current. Yes, you can see why this is important using a very small calculation. So you don't have to get out the pocket calculator, there are calculators on the internet. I've linked it below so everyone can take a look for themselves. If we now specify a winding ratio here - that is not the actual winding ratio in the NG-51 S, but I simply chose it freely, so that nice even numbers come out here. We have 50 turns on the primary side and 100 turns on the secondary side. We have an input voltage of 220 volts and a current of 1 ampere, and these values ​​come out on the secondary side, namely a voltage of 440 volts and a secondary current of 500 milliamps. Yes, and what we are going to reduce now is the number of turns, namely by half and we also reduce the voltage by half, as in the example of switching between 220 volts and 110 volts. So if we reduce these two values, then you actually have to double the current so that the result is still the same. Yes, and that is the whole reason why this complicated-looking voltage selector switch always connects different windings on the primary side in different ways: It must be ensured that no matter what input voltage is actually applied, the secondary side always comes out the same. Yes, and the manufacturers of this transformer have given some serious thought into this and the voltage selector switch ensures a connection that achieves exactly that. Here on the secondary side, the same thing always comes out, no matter what goes in. Now that we have the principle in mind, the rest is actually quite simple. That 's why we're going to more or less run through the various other settings here. At 130 volts it's very similar to what it was at 110 volts except now here we have this winding and this winding in parallel and we have this winding and this winding in parallel. You can see that too, this one is connected in series with the other one and this one is connected in series with the other one and the two green and red are parallel to each other. That means instead of 110 volts we have 130 volts and you have to add one more winding so that the whole thing achieves the same result on the secondary side. At 150 volts it's relatively similar, the only difference being that here we actually have two windings in series, namely the one up here and that. And the other two are parallel to each other. At 240 volts we have these two that are in parallel with each other and these two that are in series with each other. At 250 volts it simply runs through each winding once, so they are all in series. Yes, as I have already said, the winding of transformers and the dimensioning and calculation of transformers is an art in itself and it is quite an achievement that they have created something that can be used for such different input voltages through clever wiring of the individual windings always achieves the same result. So let's get to the front panel illumination. You could say now, that's trivial! It probably is, but with this device, so many things are not as easy as you might think. Let's take a look. We have just seen that there is a separate pair of wires coming from the secondary side of the transformer for the lighting. And these wires, they run here in this large bundle of cables up to the front of the switch unit. Here, I've marked them, they are these gray cables that you can see here. They come straight from the secondary side of the transformer and go all the way to the front here. We see them here and we see them over there as well. - there's a reason for that, because there's a little lamp here and on the other side there's one too, and this little bulb, it can give you a headache, because it's in a very, very inaccessible place. You can see that, you have to dig really deep to get to these little lights at all. And then they also point inwards, which means that if you want to swap them out, the only chance is actually to loosen the screw here so that you can pull the lamp fixture out a bit. But it remains quite fiddly and cramped and I think that's why you can find a lot of NG-51 with one or both bulbs broken. Nobody wants to go to the trouble of changing it. Yes, and the whole thing is arranged in such a way that, as I said, a pair of cables comes from the secondary side here. That goes to the first lamp and from there a second pair of cables goes away to the other lamp. Let's look at the tube heater now, which is parallel to the lamps. The tube heating makes sense to everyone: The cathode has to be heated so that it can emit electrons. But as simple as it sounds, the reality is as complicated as it is [AC heating = potential hum source]. Yeah, let's take a look at how this is actually connected. The tube heating goes through the middle of this whole tangle of cables with the circuit board version of the echolette like in this example. These are these two green wires, they also come from the secondary side of the transformer (6.3 volt winding) and simply go right into this thicket of cables. And on the other side they end at two soldering points, these are the two shown here. That 's where the cables come out and are soldered on. You can already see that a lot of other stuff is also soldered on there and we want to take a look at how the tube heating actually finds its way through the device to the various tubes. Yes, to break that down, connections marked 2 and 5 are the two ends of the 6.3 volt winding from the secondary side of the transformer. Here we have connections 1 and 4, which go on to tube 1. As a reminder, tube 1 and tube 3 in the device are the two that stand alone. And the other three are on the printed circuit board. So here are wires going to one of the stand alone tubes again and we also have these two little black wires marked 3 and 6 here that go to the magic eye filament, to the EM84, which is also in a completely different place (front panel). So that has to be routed away as an extra cable, to this remote tube. What else needs to be said here: These two cables or heating wires that now go on to tube 1 are actually shielded. This means that we have a braided shield here, which is also attached to ground at this point. On the other hand, the connections that now come directly from the secondary winding are completely unshielded, so they initially run through the cable package completely unshielded along the whole pcb. But those for the individual tubes are shielded. Yes, and the heater wires to the EM84, they just go through this blue grommet in the device through the open space in the device to the front plate. Yeah and pin 4 and 5 here are the filaments for the magic eye and that's where those two wires just go right there. I already said at the very beginning in the overview that the tube heating and the "de-hummer" are actually two inseparably connected topics. I have to introduce the de-hummer already at this point in this video. It is the potentiometer, which is located here on the outermost edge of the circuit board and we can measure it with the multimeter: The two outer connections of the potentiometer are actually connected to the soldering points, where our heating wires are attached to. This side of the potentiometer with that and the other one with that solder point. Yes, and since all three of the tubes of this circuit board echolette are of course seated directly on the circuit board, it must be the case that the heating wires are routed directly to the tubes through these pcb traces you see. Here's a very brief overview: Here we have tube 2 seen from below the pcb, for example, you can see that pins 4 and 5 are connected very directly to one end of the heating wires / their soldering point. Yes, and that trace also goes right up here to #2, which is one leg of the de-hummer pot. Over here we have the other leg of the de-hummer pot, that goes up here to one of the other two sides of the heating wire and that's how the whole thing just gets routed onto the board. Down here is the wiper of the de-hummer pot, that's ground. And so the whole thing is carried out through the whole board to the three tubes and we have pins 9 (red), 4 and 5 (marked yellow). This tube is exactly reversed, there we have 4 and 5 and there 9. 4, 5 and 9 and that is always one side of this heating wires that comes from the transformer. So here, this here is usually always connected to pin 9 and this here to pin 4 and 5. And there we have a closed circuit for the heating lines, where the heating current can flow. Yes, there we have the pin diagram for an ECC83 for illustration. We're looking at it from below, so it's practically plugged in here and that's why pin 9 is here and 4 and 5 are there, these are the heater connections. You can also see that pin 9 is the center tap of the heating filament here and it runs from pin 4 to pin 5. Yes, of course we also have to provide heating for the two stand-alone or individual tubes and I already have that said that these wires are actually connected shielded. I don't know if that's intentional or if it's just a coincidence, the assignment of pin 9 and pin 4/5 is reversed here. This means that the line that supplies pins 4 and 5 on the circuit board supplies pin 9 on the individual tubes and vice versa. Yes, with the individual tubes it is the case that the heating current goes from the circuit board to tube 1. Here's one side of that wiring that goes here. Pin 4 and 5 and here the shield. And pins 4 and 5 are bridged here and are led down to tube 3 with this red cable and the whole thing is also available on the other side for pin 9. I've now drawn a simple diagram of the whole thing here - just like it is actually connected. You may be able to see this gray crackling here in the drawing, this means that these lines are actually shielded. This means that nothing is shielded up to the de-hummer and only tubes 1 and 3 are actually designed with shielded cables for the PCB Echolette. Yes, here you can see my overlay image of the main pcb again, which I have already made available on the Internet, so you can see the whole PCB board nicely from above and below). Let's look at the connections again, here's a connection for the tube heater, it goes over here to the connection for the de-hummer and the other goes this way and up there. Yes, and from there it goes over the whole board to the tubes and what you can at least see here, which is also important: these heating lines are laid out on board over long distances completely parallel to each other. You can see it here, these two lines. Someone made an effort to really position them parallel to each other and here they are also completely parallel to each other. There are reasons for that and we'll discuss that in a moment when we talk about the de-hummer. Briefly, to name the whole thing for the sake of completeness. In the first Echolette NG-51 S series, i.e. which was still wired point-to-point and had no circuit board, the whole thing looked something like this. There are actually only unshielded wires up to tube 5. Yes, and from there everything runs parallel to each other, like a chain of christmas lights, right on through to the last tube and the de-hummer who practically terminates the individual shielding lines on his wiper to ground. Yes, of course, because the point-to-point wired echolette has significantly more cable routes, the whole thing is arranged very differently. So we see here that all shields practically end at the de-hummer, at the wiper and are grounded there. And you can also see all the heating cables here, they are routed very close to the housing, there is a reason for that, I will also address that in a moment. Let's take a look at one of the tubes in terms of how it is connected to the heating wires. So we can see here that the connections in this case really go to pins 4 and 5 and there the next cable goes to the next tube and their shields are only connected to _each other_ at the tubes at first. They are really only grounded at the de-hummer, so that we have a largely continuous screen from tube 5 down to tube 3. Yes, what's very interesting about one of my devices, I don't know if it's the same for every point-to-point wired echolette: the filament heating for the magic eye is actually taken off one of the lamps here. Well, as we saw earlier, the lighting and the tube heating are parallel to each other, so it doesn't really matter. And here is actually - probably just to save the cables and keep it short - the 6.3 volt heater for the magic eye is simply taken from one of the lamps. OK, now let's also take a look at this ominous de-hummer - what is it doing? What is it good for? I've marked it in yellow. It's a small potentiometer or a trimmer with only 200 ohms, whose wiper is grounded and the other two ends are each connected to one leg of the tube heater, as we have just shown earlier in detail . That's the de-hummer again, but let's first talk about what kind of "hum" we are actually talking about here, which the de-hummer is apparently supposed to suppress. Just two reasons, there are others, that's a very broad field. So there are two causes, one of which can be: A capacitive coupling via the transformer primary winding or EM fields, i.e. electromagnetic fields around the heating wire - i.e. a relatively high heating current flows through the heating wire - yes, and current flowing through a wire always generates an electric field around the wire and of course that can couple and leach into everything around the heating lines. This can be any component that is close to the heating cable, but of course it can also be the cathode, because the heating cable is quite close to the cathode in the tube and if there is any humming (heater voltage is 50/60 cycles AC!), then we hear it quite clearly. Yes, let's see what I mean by capacitive coupling through the primary side. So here we have the simple representation of a capacitor, that's why "capacitive coupling" - ​​capacitor. These are two plates that are separated from each other and it's easy to imagine that even with such a transformer structure, where there are also two sides that are somewhere opposite, that they also can behave in a similar way to a capacitor. So that some currents could also flow here. Yes, we are not talking about 50 Hertz parts of the current flowing through the tranny (or 60 Hertz in other countries) so not necessarily about the mains frequency, but we are definitely talking about higher-frequency interference, which today is more than ever piggy-backing on our mains frequency and if these frequencies on our mains current have a certain level or a certain frequency, then it could theoretically be that they couple capacitively directly here in the secondary side. And what we then have is a secondary current that has some weird frequencies on it that could present us with a hum of all possible pitches in the device. Of course we don't want that. The NG 51, I have to throw in, has besides the de-hummer another solution for exactly this type of hum interference, namely a shield winding in the transformer, which I have briefly mentioned earlier. So if you look at it again here. And the shield winding is a winding that lies between the primary and secondary windings, but most importantly, it is not connected anywhere on one side and it is grounded on the other side. And everything that could couple in over there is already grounded or diverted to ground through this shield winding. Yes, but the other possibility of compensating for capacitively coupled hum could theoretically also be a de-hummer. But now let's take a look at the second source of hum that the de-hummer has to take action against. We now have our transformer here - primary side and secondary side. And a voltage is induced from here to there in our 6.3 volt winding. Yes, and with induction it's just like that, if you just lay out this secondary winding, 6.3 volt winding, then the distribution of electrons in these two wires is not always exactly the same . They even differ greatly from each other, so it could even be that you have 0 volt potential here and 6.3 volt potential there and that changes the next moment. The only important thing is that we have a voltage between these two winding ends of 6.3 volts. This is the only function we need. But if the current distribution or the distributed currents differ significantly here, then it is of course the case that the EM fields that build up around these two wires are also very different. That's a problem. Why? We'll see about that in a moment. Let's take a look at what you can do about it. So one possibility would be that we make a center tap on the secondary side of this 6.3 volt winding, which we connect to ground. We have now placed this winding here at a defined 0 volt potential, right in the middle, and that ensures that these 6.3 volts result from the induced voltage of 3.15 volts up here and -3.15 volts here below. This is the principle of a center tap, which is also known from other transformers. You have practically mirrored voltages plus and minus and the tapped voltage of 6.3 volts is simply in between, because there is always only a potential difference, we don't always have to have it against 0 volts, we can also measure between these two wires . There we have 6.3 volts difference. Now it's just that it's not that easy to wind a center tap like this one hundred percent exactly to the middle, i.e. that both partial windings are absolutely exactly identical here. That's not always achievable and then we could again have the issue that the voltage distribution in these two ends is not even. Yes, and then we have a different current distribution between these two wires and then we have the problem that the EM field that forms around these two wires is not of the same strength. But even induction does not necessarily work in such a way that the same complementary voltages are always induced equally in both parts of the winding. There can always be tiny differences and that always ensures that the EM fields of these two individual lines always differ slightly, yes, and you can do the following to counteract this: You don't just put this center tap on 0 volts, you can also take this center tap out of the actual winding and make an artificial or "virtual" center tap by placing a small potentiometer between these two sides, the wiper of which is connected to the 0 volts potential, i.e. ground. The advantage now is that we can balance these two sides via this potentiometer. This means that if we have a fixed center tap here in the secondary winding, then we can't change anything about it. We can't just slide this center tap up or down the windings to suit us. But we can do that in this case by having a potentiometer here that we can dial to the left and to the right and we can actually compensate for small differences that exist here . Ideally, we really have plus 3.15 volts up here and -3.15 volts down there. Basically, the point of it all is that we have two equally strong EM fields around these two heating wires, but they have different signs +/- and thus completely cancel each other out. Ideally! In order for this to work at all, these wires must always be fairly parallel to each other and close to each other. In the past, the heating wires were also placed very close to the housing so that the EM fields were always immediately and directly diverted to ground. How this symmetrization with the de-hummer works exactly or how you can imagine it, let's just look at it in a small simulation. So, here we have a simple model of a transformer with a center tap and here we also have a small lamp on it as a load and in an ideal world it would be like that, if you really measure the voltage up here and in the lower branch of the winding, they be exactly identical, just phase-shifted 180 degrees. That is the ideal. However, I have now added a small resistance to one leg of the winding in order to simulate a certain asymmetry of these routes here. As I said, the asymmetry can come about because perhaps this center tap is not really wound exactly in the middle of the windings, but it can also simply come from other things. So we also have tubes here, these double triodes that we have in the Echolette NG-51, the heating filament has to go from pin 4 to pin 9 or from pin 5 to pin 9, it doesn't always have to be exactly the same length. There can also be slight differences in production there, so that the path may be longer on one side and we have simulated that here with a small resistor. And then we see that these voltages in the different legs are already changing significantly, which means that the electric fields around these lines could no longer cancel themselves out here at all because they were simply no longer of the same strength. Well, and that's where our de-hummer comes into play. I have now installed something like this here as an example and if we adjust the trimmer a bit, then we can also see how the partial voltages in the different legs of the winding change. And we can go to extremes, or we can arrange the whole thing in such a way that we actually have symmetrical voltages in the partial legs. That's pretty much the idea behind the de-hummer. You do it by ear, you adjust till the hum is not hearable any longer. Finally, let's take a look at the topic of rectification. Here, too, we will look at a small simulation in order to be able to understand the whole thing a little better. But first, let's take a quick look at the individual components, parts of the rectifier. Let's take a closer look at three protagonists of rectification and filtering. Here two of the cup capacitors and there the selenium bridge rectifier. Let's start with that in more detail. Yes, this Semikron model was often installed. Here's a look at the lettering: B300 C70. That means "B" = bridge rectifier and 300 is the maximum voltage that the component can handle in volts. So this is a bridge rectifier that can handle up to 300 volts. And "C 70", that's the maximum current that this bridge rectifier can deliver. So C = "current" and the 70 means 70 milliamps. Yes, otherwise this bridge rectifier has everything that is known from more modern silicon bridge rectifiers. We have two connections for the AC voltage and then we have two connections here to tap off the rectified voltage. What you can also see here is the "+" connection for the rectified voltage, which is marked in red. You can't really see it that good here right now. Yes, these selenium rectifiers, they don't exist anymore these days. I opened a defect one here. Let's take a quick look at what they look like [Caution! Selenium is toxic in higher conecentrations. Don't do this at home]. By the way, here is the red marking of the connection marked with "+", there is a red piece of plastic in there. And all the others are black. You can't really see it in the light conditions here when taking the picture. Otherwise, this rectifier consists of four contacts that are put in here like this. Then we have springs here on each of these packs, and there's actually a pack of plates in each of these squares. I'll take that out carefully. Yes, and they are actually, it is a stack of small plates, which are coated with selenium, among other things, and these are practically semiconductor plates. Yes, you can also see here that a few of them are sticking together a bit. Yes. So, we took a closer look at it. Yes, and here, as I said, it's just put on top of it and this package then presses it together really tightly - normally. That's where this red marker comes in, on the plus pole and then we would have a foil over it and this lid here, it's riveted so that the whole package is held together really tightly. Yes, the problem with these selenium rectifiers: Of course they sometimes break. Such rectifiers are no longer manufactured, it has become very rare. And if you want to exchange them, that's possible, of course. Of course, a silicon rectifier also masters the rectification technology wonderfully, but with a few differences: These rectifiers have a relatively high voltage drop, which can be 20 volts and more, and such more modern silicon rectifiers have a voltage drop of very few volts. And that's why you won't always be able to just exchange them for each other, because then the voltage after the rectifier is still too high. And that would then be 20 volts higher anode voltage in the example, you have to check in each individual case whether that causes problems or whether it is basically not a problem. Yes, if it should cause problems and you have to replace it with a silicon rectifier or maybe just four silicon diodes: I'll show you what you can do there, basically you have to put a resistor between the connection "+" of the rectifier and the following capacitor, which converts this voltage difference into heat via the resistor. So that despite a rectifier, which has a much lower voltage drop, there is no higher voltage on the capacitor. Instead of such a silicon bridge rectifier, it is also possible to simply use four diodes. For example the 1N4007, which can withstand up to 1 ampere, which is also often used in old radios to replace the rectifier. And as I said, the topic with the resistor, which you still put between + and the subsequent filtering capacitor, I'll now show you a picture. I found this on the internet, someone managed to actually fit these components into the case of their old selenium rectifier and that won't always work, the model here is relatively small. But I still think it's a cool idea, because of course you get the old look completely and you don't need a lot of space. Now let's look at the two capacitors. We have one here from a "for parts" Echolette and I almost believe that it was probably not original at all, but was exchanged before. The model comes - you can see it from the snakes - from the manufacturer "Hydra Werk" and here are a few things on it that we want to take a quick look at. Once it says "Elyt rauh", so that's an electrolytic capacitor "rough" - "rough" means that the anode, i.e. the anode foil of the capacitor, has been chemically roughened to increase the surface area. And more surface area means more capacity. That means you can squeeze the same capacitance down into a slightly smaller form factor with the rough capacitors. Yes, we have 50 + 50 microfarads, that's because this cup actually contains two capacitors. And the positive pole of the first is here, the positive pole of the second is there and the common negative pole is here on the side of the housing. We can take a closer look at that, they are screw capacitors. That means they are screwed on from the inside to the chasses. We have this plastic nut here, with a wave spring washer underneath it, which is there to keep the whole thing under tension so that nothing comes loose. It's just a corrugated metal washer. Then we have - that is now both from the inside, that is in the device - and this is now on the outside. Here we have an insulator and there we have a metal ring that is in contact with the housing. And here is practically the negative pole, the negative pole is soldered there. So, negative on the housing and here the two positive poles of the two capacitors on the bottom side, which are in this one common housing. Yes, we'll measure that right away to see whether it actually still shows 50 microfarads. Now let's look at other things here. Yes, above we have "Anwendungs Kl. HSF" (Application Class HSF). There you can see it a little more precisely, that has an HSF application class and these three designations HSF stand for the lower temperature limit at which this capacitor can still be operated, that is the first code letter. The second is the upper limit temperature and the third letter is the allowed max. humidity. And for these three values ​​there are letter codes and "H" for the lower temperature means -25 degrees, "S" for the upper temperature means +70 degrees and the "F" for the relative humidity at which this capacitor can be used, that's a bit more complicated. "F" basically stands for... the maximum annual average of around 75% humidity and then there are slightly higher values ​​- I think it can even withstand 95% for 30 days at a time. So you can ultimately use this capacitor outside in the winter and in the jungle, that's no problem at all. So it is ideal for everything in our latitudes. The next indication is "350/385 volts". These two statements refer to it: 385 it would still withstand, but for normal operation 350 is the maximum voltage at which it can be operated. But it would just endure that, after that the capacitor is dead. Now let's take a look at what capacity this one has. As I said, I'm relatively sure that it has already been exchanged, because it's a bit newer than the other one, I think. For this we take the capacitance tester and set it to the range of up to 200 microfarads. 58 to 59 microfarads. And the other side is about the same value too. Yes, these capacitors also have tolerances. I don't know exactly how it is with this model, it's often -20 to +50 percent with the very old electrolytic capacitors. Well, I think this one still fulfills the values ​​that are written on the outside. So I think you could still use it. Let's take a look at the second one, it's from a different manufacturer "Loewe Opta (Kronach)" and on the back we see a well-known name: "Valvo". Yes, it basically says the same thing on it, i.e. Elko (=electrolytic cap) 50 + 50 microfarads, dielectric strength 350 in continuous operation and peaks up to 385 volts and we have a temperature range of -20 / +70 degrees on the housing . So in principle, the values ​​are exactly the same as the other one. But the other said "rauh"/"rough". And you can also see that the "rough" one is significantly smaller. But what you can see on this large capacitor, I hope you can see that in the picture, it's crooked. That means it sticks out higher on the side. You can see that there and that is of course a bad sign when the capacitors are crooked. It almost looks to me as if it's already pushing itself out here and let's see if we can see anything from the values. So let's connect that too and measure the first side: I only measure 16 microfarads there and 17 microfarads there. Okay, so not only does it look weird, it's almost completely dead. It has almost lost its entire capacitance. Yes, that was a look at the capacitors and the rectifier. Theoretically, these can also be exchanged here, the only problem is - there are of course still 50 microfarad capacitors today, but if you take them individually, you would have to accommodate four of them in a very small space and that is of course a fundamental problem. So there are still such cup dual capacitors to buy, I will put the link in the description below. Not necessarily new ones are still for screwing into the chassis anymore, you may have to think about another thing about how to fix it there. But as far as the space requirement is concerned, these cup double capacitors are of course the only thing that can be built in there in any meaningful way. Because there isn't much space. We're going to look at some of the basics of post-rectification smoothing and filtering in this very simple simulation, just to remind ourselves why and what these different components are in the NG-51 which are actually supposed to do exactly and where the logic lies, how they are arranged. Let's get started. So we now have an AC voltage source here, amplitude 115 volts just for this test. 50 Hertz frequency, on the right side we have a meter to show us the result of this rectification, or rather how this voltage that is present here looks like. We have a small load, this is a light bulb. That helps us to recognize whether we really still have a large residual ac ripple, because then the lamp flickers, or whether we are already dealing with a perfect DC voltage - then the lamp no longer flickers. And we have here four diodes arranged in a bridge rectifier fashion. Yes, now we start the system and we can already see that the voltage still has a very large residual ripple after rectification. So that's not DC voltage yet and the instrument shows us here that we have a frequency of 100 Hertz. It's clear because the lower half-waves have been folded up by the bridge rectifier, so the periodicity has doubled and we see here that we have a voltage peak value of 114 volts and a voltage minimum of 8.93 millivolts. That means we still have quite a lot of residual ripple here and we have to get that out now, because something like that is of course not at all suitable for anode voltage, that would be a very terrible hum. How shall we do it? It starts now that we add a capacitor as a smoothing capacitor and we'll do that now. A 50 microfarad capacitor, so practically half of our first cup capacitor. And as we can see, the lamp no longer flickers, but there is still a certain residual ripple, the digits before the decimal point of the maximum and minimum are already the same, i.e. 113 volts (slight voltage drop). But the whole thing still fluctuates by at least 330 millivolts and that would not be ideal as an anode voltage either, we have to get that much smoother. How do you do that? Yes, we could definitely improve the ripple level a bit by increasing the capacitance of this capacitor. Let's remember 330 millivolts up here and we'll put a much, much larger capacitor in here and see what happens there. Yes, it has become significantly less. But the problem is, a larger capacitor also has a larger charging current and that is always a matter of calculation or consideration, because our bridge rectifier has to supply this charging current and we saw earlier that it has a maximum current that it can supply and that should not be exceeded. That's why you can't reduce or get rid of this residual ripple by simply putting a huge capacitor in here, you have to do it a little differently. And this "different" usually looks like that - a few filter elements are now used after this smoothing capacitor. And let's do that now. Yes, we have now added a filter here: From the setup you can already see that this is a first-order low-pass filter. A resistor 1 Kilo-Ohm and also again a 50 microfarad capacitor. We now have practically our first cup capacitor together. And as we can see, the residual ripple has also become very, very low. We're down to 8.26 millivolts, and that's not bad at all. Again, a small voltage drop across this resistor, that's also normal, you have to take that into account. But that can be done much better by simply adding a second low-pass filter. Again a 50 microfarad capacitor and a 10 kilo-ohm resistor and with the Echolette - we remember, we have two double capacitors - with the Echolette there is actually an additional filter element, which I have to omit here due to lack of space. That's the disadvantage of this simple simulation software, I only have this much space and I could of course arrange it a bit differently, but then it becomes confusing again. But that should be enough for us to explain the principle and if these capacitors have charged up right away, then we can see what the remaining residual ripple is here. Yes, we can now see here that the residual ripple has reached a very low microvolt range, of course we still have a further voltage drop across these filter elements, but you have to take that into account. Yes, so how can it be that these filters get rid of the residual ripple? These filters, these "low-pass filters" - as the name suggests - have a cut-off frequency and only what is below this cut-off frequency is passed on (everything above is diverted to ground). I will show here again where this cut-off frequency lies for this filter and this filter. Yes, let's take a quick look at the schematics again. I would like to show again how important the special arrangement of the smoothing and the filter elements after the smoothing is. So now we have our bridge rectifier here, we have the smoothing capacitor there, we have our 1 kilo-ohm resistor here and practically our first low-pass filter with this capacitor. Here is the 10 Kilo-Ohm and here results in the second low-pass filter and there we have another 22 Kilo-Ohm which, with this last capacitor, results in the third low-pass filter for filtering the residual ripple. And the arrangement is not entirely accidental, because after this very last filter, the anode voltage for the input amp tubes and for the tubes of the playback amplifier is provided. And we're talking about very small signals here, which of course are therefore amplified very, very strongly. And any hum that is still there with the anode voltage would be very annoying. And you would hear that very, very loud. And that's why these tubes get their power supply at the very end of the smoothing and filtering chain, and going forward it doesn't really matter that much anymore. You can supply practically everyone else, but it is very important that at the end of the filter chain there are these tubes that amplify the smallest signals and also have a very steep amplification. Finally, let's revisit one small thing. We saw earlier that one of our cup capacitors has lost almost all of its capacity. And the question is: Would you notice that now? It only had 17 microfarads and would you even notice that the thing was actually over during operation? Yes, we can take a look at what happens in the simulation if we go down from 50 microfarads to 17 here. Let's take a look at it, we're keeping a close eye on our residual ripple here. Yes, we see that the value is still very, very low. So it hasn't changed in a way that it's actually catastrophically worse now, even though that capacitor has lost almost all of its capacity. You can still see that the result is not that bad. The question is whether you would notice that this component is actually broken. Maybe it just depends a bit on where in the filter chain the broken capacitor is located. Let 's see what happens when we set the smoothing capacitor to such a low value. Yes, here too it turns out that the result is not catastrophically worse, but we have now only equipped one capacitor with a bad value the whole time. Let's do it the way it was in reality with this measured capacitor, that both halves are just bad in the same way. Let's set that to 16.5. Yes, you can see that the value is of course already considerably worse. But we're still in the microvolt range. Yes, and of course the question arises, I don't have a conclusive answer because I don't know it from my own experiments: How many of the Echolettes actually play through the world with completely broken capacitors? Because you usually still see them with their original cup capacitors. And even if these values ​​are very, very bad, there still seems to be enough headroom to still get a fairly smooth voltage out. So that's definitely exciting question. I'd be interested to know what values ​​you measure for your capacitors. Yes, I hope you stayed until the end and thank you for watching this video. And I hope to see you again next time. I would be very happy about your comments, maybe also objections, maybe I'm completely wrong somewhere. So feel free to comment, I'm looking forward to it. Until next time! Bye!