This video is titled: "The Echolette Motor. The Papst Outrunner Motor. The Heart of the German Tape Echoes." Yes, that sounds a bit exaggerated, "the heart of the German Tape echoes", but I actually see good reasons for this statement! Of course, a tape echo also consists of other important components, but without a motor there is no echo. Because it takes care of the tape transport. And the speed of the motor also determines the echo times. A stable motor speed does prevent not always desired effects such as "wow & flutter", the tape speed also has a decisive influence on the quality of the tape recording and playback. Yes, and the heart of the "German" tape echoes simply because this Papst motor that you see here on the screen, was built in different versions into the tape echoes of Klemt, Echolette and Dynacord from the late 50s until the end of the 70s. So it is "the heart of the German tape echoes" and let's take a closer look at that - with the focus on the Echolette NG 51 S, from which this engine on the screen comes from. Yes, let's start with the design of the motor. It should be noted that it consists of two large halves, the so-called stator with the electrical windings and the external rotor (Outrunner), the tip of which forms the capstan that moves the tape. Yes, and we now separate these two halves from each other, this is done first by removing this inner circlip. Then you can remove this small plastic cap from the recess and there you can see a small steel ball shining in the middle . This is the actual ball bearing of the motor shaft. And the motor shaft goes exactly through the center of the stator and is then mounted/supported here on the underside of the motor. It should be stored in some grease, this grease can still be seen here, but it has crumbled into something crumbly, so that was already very old grease and fortunately it fell out of the engine quickly and I have the rest then removed with a fine brush. So it shouldn't be like that at all, there should be nice grease in it. Yes, when that is removed, you can see a washer that rests again on a small circlip and this circlip sits in a notch on the motor shaft. When you've taken that out, all that's left at the bottom is a small plastic washer or plastic ring, it could possibly be Pertinax, it looks a bit like that. Once that has been removed, these two motor halves can be separated from each other. That doesn't happen all by itself and you either need a small extractor or you, yes, move the external rotor upwards away from the stator in a few jerky movements and this jerky pull should then also detach it from the stator. It can sometimes work better and sometimes worse, it depends on what you see in the next picture. There you can see the two separately and you can see on the treads of the stator and external rotor in this case considerable rust and the usual dirt between the ribs. This rust should of course not be there, it absolutely does not belong there. Now, of course, these treads do not necessarily lie directly on top of one another, there is still an air gap between them, but if enough rust builds up here, then it can sometimes lead to the motor being completely stuck - i.e. that nothing moves at all anymore. That would actually be a problem, but here it was still separable and I also derusted that later. At the very end of this video a few more pointers for that. Yes, what else needs to be said about the stator and external rotor is their weight. The stator has an impressive weight of 422 grams and the external rotor does not weigh much less, it weighs a whole 417 grams - and it has to be that way, which makes perfect sense, because it is desirable that the external rotor have a certain mass, because with it there is also a certain inertia. This means that once it is set in motion, it would like to keep turning and that is very good for the Synchronism of the motor. Smaller fluctuations in the drive are compensated for, it simply runs over them. So we have a good kilogram of engine in front of us. But now so much about the mechanical side of the engine, let's take a look at the electrics. The most important information is printed directly on the engine, but first something else: Here at the bottom right you can find the date of manufacture of the engine, in this case December 1965. This is of course a pretty good indication of the age of a device or it can be an indication of it, that's why this number is always particularly exciting. Next to it is the serial number of the motor and here are the important electrical facts, namely this motor would like to be operated at a voltage of 42 volts, 50 Hertz mains frequency and it would like a 48 microfarad capacitor. Don't be fooled, the big "M" stands for Micro, some other motors also have the µ symbol printed there. The 50 Hertz - I'm not sure if you have to take it too seriously, because the NG 51 S was also sold abroad and it also has a voltage selector switch and it also has various taps on the primary winding on the primary side and is therefore already suitable for other power grids ex works : 110, 120 volts. And so of course the question arises whether, for example, a US version actually had a 60 Hertz motor. I haven't seen it yet, if you know something, I would be very happy as always if you write that to me in the comments . But what you can already say: At 60 Hertz, the engine runs a little faster, of course, and we'll see why that is the case, later. Other motors were sometimes installed in other devices . In the 1970s, for example, the 220 volt versions of this motor can be found, which then also need a different motor capacitor. I think it was 2 microfarads. Yes, if we take a closer look at the engine, we must of course notice that there are 6 wires, 6 connecting wires that are color-coded in pairs, namely: yellow, yellow-black, red, red-black and green, green -black. Sometimes it is no longer so easy to tell these colors apart. Red and green in particular are then very dark and you can no longer decide what is what. What definitely helps here is to cut back this yellow protective cover a bit, because the colors have usually been preserved further back . And you can simply cover that again later with a shrink tube. Yes, and what exactly are these connections supposed to do now? I mean, the color coding and the even number in pairs of three already leaves or urges you to think in the direction: That could maybe, that could maybe be a motor with three windings. But we don't know that exactly yet, so we don't really have an understanding of how this engine is constructed from the outside . But, you have measuring devices, you have a multimeter lying around and that's why you can start to measure one or the other thing with this motor. So "one or the other", I'm talking about continuity testing and ohm's resistance or DC resistance and that's what I did. So if we start the multimeter with the continuity test on the six wires, then we find that all six wires have continuity. That is, they are all connected in some way . Now, of course, we still don't know: Is that, are these six taps on a large winding or is it perhaps three windings that are simply interconnected? We have to think a little more carefully how that could be. And what will help us next is to measure the DC resistance between the cable leads or the cable pairs. What interests me here is actually only where these taps are spatially located. So the consideration is - the further these taps are apart on the winding, the greater the DC resistance between them should actually be. So the measured values ​​will hopefully tell me how far away the taps are in relation to one another or from one another. Yes, and I did that, I did it this way that I connected one test tip to one of the wires and then I used the other test tip to measure each of the other lines. And I entered that into a matrix. Yes, and the following came out. I already said we have continuity on all six wires. And it is now noticeable here that three resistance values ​​appear again and again. And I have to say, I rounded it a little bit, so after the decimal point it changed by 1, 2 counters. So that the whole thing is clearer, I have taken the median value. Yes, and the three values ​​that keep appearing are: 31.5 - 49.1 and 55. In other words: I hung one end or one measuring tip on the yellow wire and then I with the other measuring tip I measured yellow-black. There was 31.5 ohms displayed. Then I measured the resistance between yellow and red, that was 49.1. Then the resistance between yellow and red-black, that was again 31.5. Then between yellow and green, that was 49.1 again. And between yellow and green-black, that was 55. Yes, which of course surprised me at first, these values ​​are not the same distance from one another. That is, between 31.5 and 49.1 there is a gap of 17.6 ohms and between 49.1 and 55 there is only 5.9 ohms. What does that mean? So aren't the taps evenly distributed on the winding? Let's ignore these values ​​again for a moment and just see that they increase from tap to tap. The largest measured value or the respectively larger measured value is presumably also further away spatially. In this respect, we can now write down which sections of the winding or which taps are probably next to each other. "Side by side" - I mean that between yellow and yellow-black I measured 31.5 ohms and between yellow and red-black I also measured 31.5 ohms. That's why I painted it like you see here in the lower left - that yellow-black and red-black are almost certainly right next to yellow, because that's where we measured the lowest resistance value. I did the same for the other colors. Between yellow and black there is obviously yellow and red and so on. I went through that with each of the wires and then I thought about how it can be drawn spatially so that they are always right next to each other. And that's when the circle crossed my mind because it fits, for example, if we start here with red-black: green is 31.5 ohms "away". Green-black is 49.1 away, which is the second largest number and exactly two taps apart. And red is 55 ohms away, is the furthest away. And on the other side, yellow is 31.5 away. And yellow-black is 49.1 ohms away, which means that this drawing matches the measured values ​​nicely. The higher ohm number is also further away from the starting point, so it follows that the whole thing is most likely somehow arranged in a circle. But still the big question mark still remains, why these measured resistance values ​​have such strangely odd distances? The best thing we can do now is to take a look at a little experimant, which should bring a little clarity to it. Well, I looked in the basement and found these nice big old resistors there and just measuring one and it shows me something just below 37 ohms. Well, that's almost the same as what we just measured as the DC resistance between one of these winding sections. So I thought to myself, now I'll take six of these resistors and just solder them together. First in packages of two, so that you can handle the whole thing better. Yes, the whole thing three times now. Yes, we had already found out through the simple measurement that these taps, these colored wires, had to be in a circular connection somehow and that's why I thought we'd just solder them together in a triangle, because that's possible most simple. Yes, and then we take the multimeter and now measure these individual sections. We have just seen that a single resistor has about 37 ohms and let's see if anything has changed about it. Aha, it has become significantly less! Only about 31 ohms left. And over two ... ... we're at 49. And over three? 55 barely, ah yes ... So we're back to 49 and back to around 31. Mhm, ok. Well, that's the same as what we just measured when measuring the individual wires. So we have seen in the experiment that the interconnected windings of the motor must be arranged in a triangle and connected to one another . Yes, you can now reveal the secret, because this is not a special development by Papst, but an engine principle called the "Dahlander Motor". With the Dahlander motor there is an interconnection in a triangle or in a so-called double star - that's the principle below. Yes, I want to call that the internal circuitry of the motor: So triangle and double star. And these two interconnections have the property that they enable two motor speeds with a ratio of 1: 2 to each other. That is, if we take the speed of the triangle connection as a starting point, then the speed of the double star is twice as high as that of the triangle connection. Yes, and we already know this principle from the Echolette NG 51 S, which offers two motor speeds. Now, Dahlander motors are made for 3-phase AC, so the three phases would be connected here, as is usual in our households, with a phase shift of 120 degrees between one another. But of course we don't have that with an effects device like the Echolette, because our wall outlets normally don't have three phases, instead they have just one phase and the neutral conductor connected. This is why a second principle is added to this motor, which I now call the external circuit, namely the so-called "Steinmetz circuit". With this Steinmetz circuit, only one phase and the neutral conductor are connected and a second phase or an auxiliary phase is generated via a motor capacitor. And because it is a capacitor, this second phase is not phase shifted by 120 degrees, but by 90 °. Well, an ideal capacitor would be 90 degrees, let's just say about 90 degrees. These key points should be enough for us for now, there are tons of videos on these motor circuits on YouTube that go into the general topic in much more detail and there you can find more information. We want to focus on the use of this motor in tape echoes, so we summarize the following principles again: Well, this Dahlander motor works with 1-phase alternating current. It uses an auxiliary phase via the Steinmetz circuit, i.e. a second phase via a capacitor with a phase shift of around 90 degrees. The Dahlander motor can be wired in a triangle or as a double star, sometimes it is also called star-triangle. And with the double star we have four magnetic poles, i.e. 2 pole pairs and full speed. In the triangle we have eight magnetic poles and four pole pairs and half the speed. Pairs of poles can be thought of as in the case of a permanent magnet; so a pair, that is the north and south poles. And the north pole is a pole and the south pole is a pole. And together they form a "pole pair". With 4 magnetic poles we have twice north and twice south, where the comparison with the permanent magnet already ends, because it is an electromagnetic field and because we have alternating current, the north and south poles are constantly jumping back and forth or change sides. Electromagnetic field: This creates a rotating field and this rotating field has a speed. that can be summarized with a formula and that is this formula here. That (f) is the mains frequency divided by the pole pairs (P) - and because we want the revolutions per minute, we take the whole thing x60. That means if you fill it with numbers. We have 50 Hertz and 2 pole pairs and the whole x60. Then there is a speed of 1500 rpm and if we have 50 Hertz and 4 polar pairs and take the whole x60, because the denominator has now become larger, i.e. before 2 and now 4, the number naturally becomes smaller. That is then only 750. So with 2 pairs of poles 1500 revolutions per minute. With four pairs of poles 750 revolutions per minute and if you only had one polar pair, it would be 3000 revolutions per minute. But now there is a little "BUT": I have a "sync" written in brackets, which means that these revolutions per minute refer to the rotating field. In other words, this magnetic field that rotates around the axis of rotation of the motor. This is the speed at which this rotating field rotates. And now there are motors where the rotor rotates at exactly this speed - these are called synchronous motors. But we are dealing with an asynchronous motor here, which lags a little behind the rotating field, so it is a little bit slower. So we can take this number as an approximation, but we have to keep in mind that the motor of the Echolette is an asynchronous motor, that is, it is a little bit slower. Maybe about five percent. We'll measure that later and see what exactly we get out of it. So now we come to the wiring of the motor; We will recapitulate here again very briefly: the switchover between triangle and double star is done by rewiring the six connections and this rewiring must necessarily be done via the switchboard of the Echolette. Thats why we have two buttons here - "Short" and "Long". So fast speed, that would be the double star and slow speed, that would be the interconnection in the triangle. Because if the tape is moved forward more slowly, then we have the longer echo time. And the faster tape gives us a shorter echo time. On the left side we see the two switches "Short" and "Long", just for a better understanding, we are looking from above into the upturned Echolette. We see this picture, what we see here, when we turn the echolette upside down as in the picture right and look into it from above . We will keep this line of sight now, only that there is no confusion as to how exactly it is now connected. So these switches work in such a way that we have four groups of three terminals: 1, 2, 3, 4. And these four groups initially have no connection at all, that is, each of these groups of three stands on its own and when you push the switch, then the two upper contacts of each group are short-circuited or bridged with one another. And when the switch pops out, the two lower contacts are short-circuited together. When the engine is running quickly, the "Short" switch is pressed in and the "Long" switch is out. When the engine is running slowly, the "Long" switch is pressed in and the "Short" switch has jumped out. When one switch is pressed, the other will automatically pop out. How exactly does that work now? So let's first take a look at the mechanical side of this panel. The white buttons are attached to long flaps, some of which protrude from the rear of the control panel. Above the white buttons there is a spring that gives the switch a restoring torque that is needed so that it can pop out afterwards. There are two things to say about this flap, first it has a nose here and a slot there. That will be important later. At the upper end these flaps meet another flap that is offset by 90 degrees, i.e. a transverse flap and this in turn also presses against a spring on the left. Here you can see it enlarged. This spring gives this transverse link a restoring torque, so that it can automatically jump to the right again afterwards. So this is there to load this whole mechanism. How exactly does this control panel work? This cross flap has an inclined notch, I showed this here as a small single image. So here we have a slant and if you press a button in now, the nose of this button tab hits the slant and moves the cross flap a little to the left. Until the nose arrives at the upper end and goes over this edge. Then the cross flap, driven by its spring, jumps to the right again and the button is locked on this small plateau. If another button is pressed, the same thing happens in its place: The tab is shifted to the left again when the nose slowly climbs up the incline and by moving the tab to the left again, the nose of the switch that has just been locked jumps again out and the button disengages. Put back by his spring. That means: push in, lock, push in, lock - and it jumps out again. Let's take a closer look in a slightly slowed-down video. In order to understand how these contact pairs are made, let's take the complete switch apart. This consists of two parts, namely a slide and a bar with the soldering lugs. There are four bridges on the slide that have a slot in the middle so that the upper soldering bar or contact bar can move back and forth in this slot . Two of them are connected to form a bridge. The upper part of the switch with the solder bars is firmly attached to the switch panel, only the slide can move back and forth. The slide is moved by a tab on its underside that hooks into the slot of our brass flap. This means that when we push the switch in, this slot collects the slide with it at this point. And it is pushed back and forth with it's contact pairs of two . Because there are always pairs of two here, on the slider, two of these contacts on the fixed solder strip above are bridged with each other. Let's recap: When pressed in, the top two contacts are short-circuited with each other and when the button is released, it is the bottom two. Now let's take a look at the wiring of the soldering lugs: We already know that there are six wires coming out of the motor and needing to be connected somewhere. This is our internal circuit and we know that the power supply has to be added as well. Because the principle of the Dahlander motor in the Steinmetz circuit requires a phase, then at least one wire from a capacitor and the neutral conductor. And they all have to be connected somewhere, so there are a few wires that now have to be placed on these switches . And that is again very confusing and that is usually the reason for the biggest question marks in front of your eyes when you look at this control panel a bit. So let's start with just looking at the wires that are soldered to these switches from the motor. There we have our six colored wires again and, most importantly, a jumper, which will make sense later. But these three contacts must actually be jumpered to one another and it now looks like this on this switch. There is a solid wire and one, yes, a small cable, which is running along here. Now what happens at this point when you press the switch? When the motor is running fast, the "Short" switch is pressed and the "Long" switch has jumped out. I have again marked in yellow which of the contacts are connected to each other and what I would like to point out at this point is that our three black-striped cables or wires are connected to one another through this jumper . If we want to reconcile this with our view of the Dahlander motor, then we see that when the motor is running fast we have the star connection or the double star, because with these the black striped wires are connected to one another. And the simple colored ones: green, red, yellow - they are connected to something else, which we will look at in a moment. When the motor is running slowly , the "Long" switch is pressed and the "Short" switch has jumped out and we can see here that our three colored-black-striped wires are no longer connected to each other. But they are now individually connected to something else and that corresponds to the Dahlander principle of the triangle connection for slow motor speed. Now we add the external wiring, i.e. the power supply. So that it doesn't get too confusing, let's look at the fast and slow motor speed in single images. We can now see that when the motor is running fast, the green wire from the engine is connected to a blue-yellow one. The red wire is connected to a yellow-red and the yellow wire is connected to a red-yellow. This is also reflected on the actual image from the Echolette: We have the blue and yellow wire here, there the yellow and red wire, and here the red-yellow wire. When the engine is running slowly, the single-colored wires green, red and yellow are actually no longer connected to anything. And instead, our three black-striped wires are connected to the power supply. It should be pointed out that the lead of the yellow-black wire also comes from the "Short" switch, via a jumper. This is a massive wire bridge that is soldered in here. So when the engine is running slowly, green-black is connected to blue-yellow and red-black is connected to yellow-red and yellow-black is connected to red-yellow. I think now is the right moment to take a look at an excerpt from the circuit schematics of the Echolette NG 51 and only the excerpt that interests us here. We see the following things on this circuit diagram : For one here the 42 volt winding on the primary side of our transformer, we see the fuse of the device, we see the motor and we see the two switches here. We have the voltage selector switch here on the right-hand side and - last but not least - we have our 48 microfarad motor capacitor at this point . First, let's look again at a simplified wiring. These are the actual connections as we see them in the device. I removed everything on a "for parts" Echolette NG 51 and because everything inside is tightly tied together with small cords at the factory - a contemporary practice one has to say - it's ike macrame or bondage - depending on whether you are an esthete or a masochist. So there every wire is neatly tied together and it's a bit difficult to see what is going where. And that's why I split it all up. Yes, and what we then see here is the primary side of the transformer and we have the blue-yellow wire here and the red-yellow wire down there, that's the first surprise: Because the 42 volt winding is not right next to each other, but these are the two outermost connections of the transformer. Yes, the red and yellow wire goes from one side of the 42 volt winding to the outer conductor of the fuse holder, this is the one here, and from there a red and yellow wire goes to the mains selector switch, we can see that here. Namely to connection 1 of the mains selector switch. They are numbered here: 4, 3, 2, 1. And from there a single red and yellow wire goes to the motor capacitor. You can still see that here, I cut them off, the two red and yellow wires. So one of them comes from the power selector switch and goes down on a second wire to the buttons. And on the other side we see the yellow-red wire that goes to the buttons too. And from the other side of the 42 volt winding, the third, the blue-yellow one, goes down to our "Short" and "Long" buttons. Yes, I have now drawn that in as it can actually be seen in the device with cable colors. And one last comment on this link. On the circuit diagram, of course, everything always looks as if it is a continuous line, but of course here too: We have a blue-yellow one that goes to the first switch and a yellow-red one that goes to the first switch . And from there they go over to the other switch as a second cable. And these windings are relatively long here because they are also in this cable package. So don't be fooled, it always looks like these two lines are coming out of this cable package somewhere, but they are actually ... they all go to the first switch and from there as the second cable to the second. Yes, we have now also added the cables that come from the motor. Now the whole thing is already extremely colorful. What else you have to say about this circuit diagram, because it can also confuse you completely: This line here is not the edge of the switch that has been artistically inserted here, but this is our jumper on the second switch, which in reality actually rather goes there in the middle. It is drawn as the outer line on the circuit diagram, so don't let this confuse you. Yes, the circuitry of the motor can be broken down to the very simplest, as shown in these following two pictures: For the slow speed you link yellow-red with red-black and red-yellow with yellow-black and blue-yellow with green-black, then you have the slow motor speed. And for the fast one you link yellow-red with red, red-yellow with yellow, blue-yellow with green and I drew this a bit stupid, That is only supposed to mean that the black-striped wires are _connected_ to each other. they are not connected to these three wires [power supply] here. So they are only connected to each other. Yes, that was, in a nutshell, the theory for the Circuitry of the motor. Now let's look at the motor in real and some of its functionality in some experiments. And I hope it will be exciting again. So let's see a few experiments. We're going to wire the motor for slow speed first. Only the black-striped coloured wires are now connected. The simply colored wires just hang in the air unterminated. Now the speed measurement with the laser gun. Around 728, 729 rpm. And now we wire the motor for the fast speed. Here the simpl colored wires are now connected to the power supply and the wires with the colored-black edging, we will simply wire them all together using this little terminal. And here again the speed measurement. And we're about twice that, 1400 revolutions per minute. And now it's getting interesting, now we're just gonna exchange the red with the green wire - or as in the case - the red-black with the green-black and see what happens then ... the motor then simply runs in the other direction, in that case counterclockwise. And lastly, what happens if we disconnect the capacitor? At first nothing happens, but if we give the motor a little spin in the direction of rotation, then after a short time it will accelerate to its full speed of rotation. This means that the capacitor is initially only required for start-up. Yes, we've already seen it, this motor was very very rusted and I will now just use a brass brush, a relatively soft brush, I'll remove the rust. And that with a glass brush the extra dirt. Yes, and now let's take a speedy look at it. Let's reassemble the storage and there will also be a little bit of grease in there and when everything is assembled, the engine is good to be used again. Finally, let's listen to an example of how the engine sounds before and after the maintenance. That speaks for itself. To conclude, let's talk again about a problem that we unfortunately made ourselves. The preparatory work for this video took a couple of weeks and I also have experimented a lot with the motor in the process and two weeks ago I also took a measurement of the current that flows when the engine is turned on and when the engine is running. And when I turned it on, I had about a Current of, yes, 600-650 milliamps maybe for a second. And after that it fell to slightly below 300 milliamps. However, during the last recordings I noticed that the current during operation is now almost twice as high. It's about at 650 milliamps, which is absolutely not okay. You have to keep in mind that the Echolette just has a 300 milliampere fuse [but slow blow!] and it would definitely trip at the moment or shortly after the engine starts. So what happened? Ultimately, a hint arises from one little test. I slowly turned up the voltage here and the engine started now to run at about 10 volts. In my first tests it only got running at 30 volts. And here on the clamp meter, you can see how the current is slowly rising ever higher [Info Box: The magnetic field needs a certain current flow through the windings to built up to it's full extend. If this happens at lower voltages, than something must have changed with the inner resistance of the curcuit] [Info Box: The magnetic field needs a certain current flow through the windings to built up to it's full extend. If this happens at lower voltages, than something must have changed with the inner resistance of the curcuit] My guess is: in the meantime I did a little test, where I wanted to measure the phase shift of the capacitor and i ran into a small mistake wiring this up but it most likely had a bigger impact. Namely I fabricated a short circuit and my isolating transformer started to hum very strongly. His fuse which is rated at four amperes, however, has not yet blown. I suspect that in doing so So much current flowed for a short time that something broke in the motor. I can not think of another explanation. because now, at 40 volts, a current that is much too high is flowing - and that is can only be explained by the fact that there is now perhaps a winding short in the motor. Of course I have again measured the resistance of the individual wire pairs or the resistance between the individual wire pairs, it has also decreased somewhat. Only by a few Ohms, but nonetheless, that's the only explanation for me. And that's why I have probably wrecked this motor: well, you have to learn the hard way every now and then, the important thing is that you learn something from it. And with that I say goodbye, see you next time. Take care!