Neat Electronic Device from 1939 Explained with Restoration

hi there and welcome to another episode of mr. Carlson's lab today we're going to take a look at an interesting device from I'm guessing the early 40s era really not too sure because there is no literature or information available on it but looks to be around that area so what I'm going to do is open this thing up and that'll give us a better idea of when this thing was put together and should get a little bit closer to the date so what this device does is well first of all it's a Sylvania electronic switch and this thing is intention was to give very early oscilloscopes dual-trace capabilities so way back when this is you know some pretty special stuff especially in the forties era so I picked this thing up off of a ham swapmeet table and I'm really hoping that this thing isn't a charcoal briquette inside if it is we'll make it work anyways but you know it's just a little bit more work if it is so hopefully it's in good condition what we're going to do is go through the thing I'll probably end up drawing a schematic on this thing or something so I can explain it a little bit better and I'll restore the thing we'll try it out with an old oscilloscope and see how well this thing makes two traces on a single oscilloscope screen so let's get started here's a closer look at the face of the electronic switch and as you can see it's in pretty nice condition aside from a whole bunch of surface dirt bunch of surface dirt on the top of the cabinet as well nothing that a mild detergent really wouldn't fix unfortunately somebody was overzealous with a tested stamp has tested here here here there's some red printing here that's smudge that's the same color as the tested stamp and up here as well so must have been a slow day somewhere right about the model number here where it says type 104 the number 116 is stamped on the top here and it's a really nice job rate above the Sylvania is the letter B so I imagine that that's a serial number there is no other writing or printing on the outside of the case then you know other than what's right here so maybe the hundred and sixteenth one that's been made this came from the industrial apparatus plant so I imagine that this was intended to be in some form of an industrial application so I'm expecting you know pretty good build quality inside this switch is probably be close to the first of its kind and I imagine you know this was new technology back then so this thing was probably worth a fair chunk of money down on the bottom here you have a tag that really doesn't mean anything this could have been put on at any point in time this is okay and then number 22 this is a ground lug on the bottom here so our ground binding posts we have an input binding post a and an input binding post B you'll notice that they don't use anything like a B and C jack or anything on the front of these units and that's because back in the day when these oscilloscopes were out they just used wires to tie into the oscilloscope so basically twisted pair now this is going to be a low frequency device I imagine it would probably be within the audio bull range somewhere so this would be a common ground so if you were to have a twisted pair running to input a it would be like this and then 2 B would be like this like here so you would tie the grounds or the comments together and put them onto the ground down here I don't know whether this is isolated from the case or not at this point it looks like there's some form of a wafer in behind here insulating it from the case but we'll find that out here in a little bit this would be the output side we have ground here and output so this is the outputs going to go to the vertical input on an oscilloscope and the ground would just go to the oscilloscope ground we have gained a and gain B here so this is obviously going to set the gain of a input a and set the gain of input B where in the chain of events these are tied in on the inside of this box I really don't know at this point but we're going to find that out together they have different colored chickenhead knobs on the gaining and gain B than the rest of them I don't know if it was factory like that but it does look nice and I'll just leave them on there in that middle here it has a balance control so this is obviously balancing something out inside maybe to balance out gain a and gain B so that you know that the signals rise evenly and fall evenly at this point I really don't know again we'll find this out green jewel lamp on the front most likely to indicate the power on and off range control for an oscillator inside and a frequency adjustment so to give you an idea say this range three okay and we were to put this down at the bottom that would mean that this is at the bottom of range three or the top of range two and then if we turn the frequency control all the way up to 100 that would mean that the frequency would be at the top of range three or the bottom of range four so you can see we'd have quite a range but using all of these different settings here so obviously some form of a wafer switch inside probably capacitors on it or something like that set up somewhat like an old oscilloscope would be set up again we'll find this out when we look inside so the line cord here is in pretty bad condition with a plug here look at the plug so you know this might actually be a blessing in disguise you know so I imagine the rubber got hard somebody stepped on it and cracked it so if this happened hopefully a long time ago that would mean that nobody has tried to apply any power to this thing and possibly burn up the power transformer in here a lot of people like to plug these old devices in old radios and old tests gear just to see the you know that if the Joule lamp on the front glows and while the Joule lamp is no comfortably glowing on the front smoke is you know starting to pour out of the side because the high voltage section is shorted or something like that so I'm really hoping that the power transformer and everything inside this thing is in good condition hopefully this year it's really heavy now hopefully there's no rocks or charcoal in this thing so we'll find out again it looks you know like it would be a you know a pretty pricey device back in the day in fact this here feels like it's actually standing off of the paint here so yeah so same with this here as well so anyways again it it looks like it would most likely be a you know a relatively expensive device way back when so so probably a nice build quality so again what we're going to do is get this thing working you know if it's not working not a big deal we'll make it work I'm not really too concerned about that I have lots of power transformers and whatever it just means that you know we're just going to spend more time in this thing together and this is going to end up on that older test bench that I've been talking about in my other videos now in some of my earlier videos I mentioned that I'm putting in older testbench together with lots of old tests cure and we're going to serve as newer modern devices with this really old test cure and we're going to also use this to service gear of the day so you know service will radios back in the 30s and 40s and things like that the only thing that's really different about the test gear of yesteryear and the stuff nowadays is of course you know the new stuff there's more bells and whistles and you really don't have to think all that much to use it this older test gear requires quite a bit more brain work to operate and I'll show you how to work all of this old stuff and again we're going to fix things together again you know the Tet the actual test bench that I'm putting together is taking some time you know just because this daily life right I'm trying to get everything all together here and get this other I guess you could call it secondary lab put together but it is coming along it's a slow process and as I find time and I just work on it put a little bit of time in here and there so this will be in a completely separate room with a whole lot of other old test gear and we'll do some pretty neat experiments in there as well again coming in the future so so what I'm going to do now is turn this thing around we're going to take a look at the backside here and I'll probably cut the cord off can assist some pretty ratty condition and we'll just go inside the unit here and see how the thing looks and determine what we're up against this is the back of the unit and it looks like these are the only two screws that are holding the case on so I'll remove these and we'll go inside but the first thing I'm going to do is get rid of this line cord so it's out of there it's a pretty ugly looking line cord so move these two screws of course they are fine threads I'm glad I'm using this okay here see what we've got it feels like it's gonna come on every little device it's looking like some pretty good build quality already and that case is heavy it's got to be that's easily 12 gauge steel from that case that case is probably half of this thing's weight Wow so let's take a look at the top first so the first thing I can see is we've got a bunch of goat shields so these are spelt go8 II like the billy goat and what these do is these just shield the glass tube underneath so that other things can't interfere with a tube and vice versa these can't interfere with other things so just a big big metal shield over to the top of the tube that's all very easy to get off let's pull the top cap off like this take the cap off the top of the vacuum tube and split the shield apart and away you go and you can just pull a vacuum tube braid out so there's two of them there the tubes are six j7s now 67 tubes are pretty common in older radio receivers are used as mixers so they're using these obviously for some form of mixing 6k sixes we're used as audio output tubes in some of the earlier receivers as well so what they're doing with these on this chassis right now we'll have to find out there's a seven and seven in the center here this is a locked old type tube so that kind of gives us an idea of the date possibly of the you know when this thing was put together look a little more into that I don't want to say anything yet so a seven and seven is a dual triode so they're most likely using this tube as the oscillator now a little trick with a seven and seven or any type of a lockable tube is they've got a dimple on one side so these are known as octal tubes they have an indexing pin in the center so you can only put these in one way and that is the indexing pin you see little index there hope all right so that you just put them on the top here give them a slight turn and they'll kind of fall and then you can just push them in these are a little bit different they lock into place and this really became a favorite amongst automobile manufacturers for the car radios so the secret is a little dimple on the side in order to get these out of the lock tool socket you bend the tube towards the dimple and they kind of pop out just like that and it lets off and you can see that there is a little ring on the bottom there that locks the tube into place so in the older car radios these things would be held tight in the socket and they wouldn't vibrate and fall out there's a little dimple so if you're ever going to removal octal tube these are also you know in Philco radios and things like that as well so if you're ever going to take these out always just bend the tube towards the dimple and then pull up and it should release it from the lock it's a little dimples there for so there it is rectifier what is that 5y for so full wave rectifier over here and we have two filter capacitors these are rated and 40 micro farad's at 450 so these will be replaced with 247 micro farad capacitors are both the same thing it says there and it looks like somebody's replaced one of these be ours these are different so I'll have to look into that and also am I going to notice on the top before I move this it's really nice construction the chassis so nice and everything it really nice job with this on the bottom side and see here oh my god see if I got the light in here so it looks somewhat decent so here's that way for switch with a bunch of capacitors on it and it has a solar sealed tight capacitors and there's a 39 on there which might date this thing if I remember correctly I think the lock dole tube was introduced in late 37 or 1938 and this being 39 that might be a good way to date this thing and of course with these these tubes here whenever you see tubes that have this this kind of a that I guess you could call it a shoulder because that's what they're actually called sometimes they call them coke bottle tubes they have a whole bunch of different names for things for these tubes but they're they're actually called an ST style two boar shoulder type and that's what this is this is a shoulder type so whenever you see an old tube that's a shoulder type tube you know that it's pretty early again another shoulder type tube right over here right and it looks like all the tubes are still all original look at that we all have an interesting little symbol on the side that looks like a little leaf look at that there it is there Sylvania Sylvania Sylvania and this one here is the same thing a little leaf Sylvania so it'll be interesting to pull these two tubes out and see if they're Sylvania tubes as well maybe this is a you know has really low time on it but you know you see there's a 78 on this and then there's also a stamp on this one here as well so maybe this was just a replacement or they just had they were changing a batch when they were putting this thing together 78 looks like it's just 78 on there as well very interesting maybe that is factory so many things to take note of so yeah bunch of capacitors solar sealed tight capacitors so if you can see that there is a sealed tight on there see down there they're sealed tight to keep the leakage in so you know that these things are horribly leaky by now all of these will be leakage wax ends on these things so these will have to be changed same with these and here so quite a bit of work to do in order to bring this thing back let's take a closer look at the bottom portion of the chassis and get a better idea of what the engineers were thinking of back in the day when they put this thing together this really does read off like another story so first of all some of the easiest components to notice are these really big 1 micro farad capacitors got one micro farad 400 volts on this side same on this side here now if you notice something if you were to divide the chassis into two here you'll notice that we have pretty much two identical sides and that's because we have two identical channels channel a and channel B to see lights here to see lights here and left early here and I left your let it cure a bunch of resistors here a bunch of resistors here now you'll notice the size difference between this electrolytic capacitor and this one here but they're both rated the same they're both four micro farad now the reason that they may have done that is just for size consideration or they may have bought up a different lot of capacitors and they're just using them up way back when they do the same thing that they do nowadays is if they can get a better price on a different lot of capacitors they'll do it just to cut cut their costs so you'll notice this a lot in some of the early radios as well little early receivers you'll notice a four seven pin miniature tubes and then right out of the blue there's like an octal converter tube or something like that in the chasse and you're like why what have they done here the reason being is they probably had maybe a hundred thousand octal converter tubes left over so they just want to use them up so what they'll do is they'll punch a larger hole in the chassis and put an octal tube in there instead of a 7 pin miniature it's very very common and in fact you may have come across one of these radios I've come across plenty that they've done that in just different manufacturers this is a filtered choke over here so this is doing some filtering for us taking a little bit of ripple out we have our fuse down here line cord that we cut another capacitor here here we have a large variable resistor of some sort this is to be determined what they're doing and a bunch of mica capacitor so the mic is most likely won't need to be replaced these steel tights are going to have to go these are going to have to go these electrolytic sar going to have to go I'll test all these resistors these are round e type resistors and a lot of the times they really move in value so I'm going to check all of these I want to make the channels very close so that we can get some pretty consistent results between two channels here when we're doing our experimentation so I'll test these resistors up here again more Roundy's you know one here and one here on this potentiometer here so in order for me to really explain what's going on in here I'm going to have to draw this up so what I'm gonna have to do is probably you know cut one end of these one mic capacitors and lift them out of the area and I'll just drop a schematic for this entire unit here and then that way I can explain better what's going on in this unit just before I do that though we'll take a look at the top end of the chassis a little closer look at that here's closer look at the upper portion of the chassis and you can see that we've got these goat shields here I'll show you how to remove these it's really quite easy what you do is you just remove this top cap here now this is a grid cap on this particular type of tube not to be confused with a plate cap on some of the transmitting tubes the signal is going to be going in here whereas on some of the larger power tubes the plate cap is where the high voltage goes in so you need to know the differences you wouldn't want to be touching something like this unless you knew that the high voltage was discharged again this is where the signal goes in this is a grid cap not a plate cap so you just pull that off and in order to get these out all you do is you just hold onto the tube and pull the shield rock it a little bit pull the shield and the two boat together they are in there pretty tight now you got to be careful with these things that you don't cut yourself because these are just basically stamped and these edges are razor sharp on all of these things so just make sure that you don't cut yourself these things they just split apart in two like this and you get your tube oh look at that Sylvania it's got the leaf on it as well so when we look at all of these tubes here they all have that little Sylvain leaf on them you know even the even a locked old type tube here so there are all the same the locked on table just bend it towards that dimple air take it out again even that little leaf on that one as well the lock there's a better look at the lock on the bottom and there's the indexing pin on this one here so you have to align the indexing pin up close to a lock goal or close to the octal type tube but the reason they are called the lock tool is because of this little area right in here that just snaps it down into place so just like so and they stay in there really quite a quite a well mounted tube so very good for automotive use back in the day so that's a look at the upper portion of the chassis there's that VR on the other side see how these all have this red number on it this has got looks to be like a 78 or 76 kind of smeared hard to say same thing over here so again maybe they're just using different lots of components so they may have bought up a bunch of again different Lots and they're using up this one here and this particular style over here a few hours later well more accurately about three and a half hours later we have a schematic for this entire device this is everything that's inside that little electronic switch now whenever I go about reverse engineering something whether it be vacuum tube or solid-state what I do is I just pick a corner I start with pencil and paper and just an eraser and I'll start drawing so I usually pick an extreme end of a circuit so at this at this point here I started at the 6j seven and I worked my way towards the seven and seven oscillator get started this end and work this way as well just whatever you're comfortable with you'll find when you start drawing schematics on a piece of paper that sometimes things get a little bit too condensed because of just the amount of components so you'll find yourself erasing things spreading things apart and then redrawing again and in fact I redrew the schematic a couple of times just because of component density see here the length of the screen grid line has to come way out to here so I can draw these two components in and that one's out to the balance control originally you know I've started with you know short screen grid leads and then you find that I got to add a cap and a resistor in so your erase it and then after a while the schematic starts to look ratty so then you just start over again this is just standard stuff whenever you're reverse engineering and of course while you're doing this you're trying to keep this as clear for your own reference as possible and in this case I'm trying to keep this as clear for my reference and yours as well now after I'm finished drawing an entire schematic what I do is I take that and I photocopy it and I turn the pencil into basically black ink reason being is because graphite glares in the camera now I've drawn in one resistor value in graphite and you can see the result I'll just lift the corner of the paper and it does that all the time and you can really see how like some of the graphite will even try and blend with the paper and you can see that it's fooled this line here it's fooled even the copier a little bit it's gotten really pale but this is actually a really dark line this is just standard I guess it's just the way that the pencil creases the paper while you while you're doing your drawing so at any rate so that's what I do you can tell that this is a photocopy because this is a line over here and then after I've done this then it's pretty much ready to present now I could take the time and draw this out on my schematic program and really spend a lot of time with it but you know this is completely you know I can completely understand this and it's pretty clear so not only that you know the amount of time involved in that would take a quite a while as well to redo this you know and if you're going to redraw this in a schematic program you have to find things like rings range switches with four positions something that can be gained and things like that so just draw it as clear as possible and I just usually end it at that point at any rate so when you start reverse engineering either a point-to-point device or a solid-state piece of equipment sometimes you're going to find components that are in the way and in point-to-point devices that is very common for example these capacitors there is two of these there's this one here and this one over here and they cover up a lot of the circuitry that is underneath here basically hiding things so in my case I'm just going to replace these so I just took these things out now if you're uncomfortable with completely removing components during a reverse engineering process you can D solder one end and then bend the component up and then look around it and draw everything and then if you're careful when you bend this thing back usually they fall right back onto the area that you've disordered it from so that sometimes makes things a little bit easier if you're uncomfortable with completely removing a component one thing that was really an issue with this one here is the 7m7 tube socket is completely under all of these capacitors on the range switch so it looked like a cluster of wires running to the seven and seven tube socket just a big jumble of wires into this little area and then that was it you really couldn't see much of the tube socket so in order to reverse engineer something like this you would want to remove everything out of the way much like I did so that I can have a clear view of the socket and I can follow each wire directly to the pin another thing that's a little bit of an issue with lock tool type tube sockets is from the bottom sometimes it's a little bit hard to indicate where the locking pin is because it kind of hides above the lock they're not as easy to spot as an octal type tube socket so that's another thing you got to locate the locking pin or the index on the locking pin and that way you'll be able to count pin number one when you look at a bottom of a tube socket the tubes always start from the index if the index was here this would be pin one two three four five six seven and eight and then you'd be back at the index pin again so you'll always count clockwise on the bottom portion of a tube socket no matter what vacuum tube it is you always count clockwise on the bottom so how this schematic works is if you look at the seven n seven seven and seven tube is nothing more than a six SN 7 to package din a lock tool type a package release all day done so they've taken the guts out of a six sn7 and put them into a lock tool type tube the reason that they've done that is so that they can make a rugged version of the success in seven that will pop out of its tube socket in mobile use that's the reason that they did that so 6 SN 7 equals seven and seven seem to just different base that's all now if we look at the 7 n 7 tube here you can see we have one trial on this side and another trial on this side you'll notice that the grid of this triode connects to the plate through this capacitor and you'll notice the grid of this triode connects to the plate of this capacitor this makes a nice little oscillator that will go back and forth like this now from pin 6 we have a 1 micro farad capacitor that was these really large capacitors here acting as a DC block and that's connected to the control grid of the 6 k6 the 6 k6 tube is a power pentode and i haven't drawn in the third grid the third grade is the suppressor grid there is no reason to draw that grid in just because it's connected internally to the cathode and you'll notice a lot of these tubes 6 k 6 is 6 v 6 no 6 F 6 all that they all draw these particular tubes you know without a suppressor grid no mind you some of those are classified as being touch rows and things like this but the 6 K 6 is a pen toad and just for ease of understanding I've drawn this as a tetra you'll find this in a lot of schematics they do this just to make things a bit easier to understand so the fixed K 6 itself is triode connected whenever you hear the term triode connected all that means is they've tied the screen grid to the plate and they're basically using it as a triode the 6 K 6 is configured as a cathode following since this is a power Pento this is going to be a pretty stout cathode follower so what's going to happen is is we're gonna have an oscillation going back and forth here this is going to block the DC from the plate but it's going to allow that pulse to come through what's going to happen is we're going to get a pulse onto the control grid of the 6 K 6 the 6 K 6 is going to turn on because if you bring the voltage on the grid positive the tube is going to turn on now when a vacuum tube turns on if you want to picture this mechanically you can picture the cathode trying to connect to the plate so it's trying to act like a switch it's trying to connect this to the plate so more so like a big variable resistor the more voltage you put on the control grid here the more this is going to try and conduct alright so what's going to happen now is we're going to receive a pulse here the plate voltage here is going to try to connect to the cathode it's going to lift the level of the cathode here you'll notice that the cathode of the 6k 6 in the 6 j7 are tied together on both sides through a 2k resistor to ground the cathodes have to be tied to ground because then the tube needs some form of a ground reference so it's tied to ground and the two kate lifts the cathode off of ground to apply some bias to the circuit now what happens with a vacuum tube and a lot of people get confused around the biasing of vacuum tubes and I'm going to go through this in the future I'm going to spend an entire video episode just talking about biasing up power tubes and triodes and Iowa also in the future go through a video about reverse engineering as well I meant to mention that earlier I'll pick an easy vacuum tube circuit and we'll reverse engineer it together and I'll also pick an easy solid-state circuit with a circuit board and we'll reverse engineer that too and I'll show you the steps in doing that a lot of people think that point-to-point wiring is much easier to reverse engineer then then circuit board stuff actually it's quite the opposite a lot of circuit boards you can shine a light in the bottom and look right through the circuit board and see the traces on the other side providing there's not a big ground plane layer and hidden vias and things like that most of the time it's it's very you know possible to do that whereas this yeah wires hiding behind things they're they're coming up behind boards and being tied in and odd places you know what's even really bad about some of these manufacturers is they put looms of wire together with the same colored wire and we're talking like a loom of 25 wires and they're just bloom together all the same colors so you have to own things No so my own experience reverse engineering circuit boards solid-state equipment the modern stuff to reverse engineering this old stuff actually the old stuff is is a little bit more time-consuming to reverse engineer at any rate getting back to the schematic here so we have both of these cathodes tied together and they're lifted above ground here alright so there it's going to be applying some bias to these tubes here now when you lift a vacuum tube above ground save save that duh there's 8 volts on the cathode here because it's you know going through this 2k resistor we'll just use that as an example say there's 8 volts on the cathode that looks like negative 8 volts to the grid because you're lifting that above ground so it looks like negative 8 volts on the grid and it basically that's what they use for bias that's the reason that you see cathode resistors on vacuum tubes it's just to bias that stage up when you see a capacitor across their resistor basically it's just acting as a bypass capacitor so it's allowing a path for the AC to flow that's what's happening here so in this circuit we have 2 K lifting both of these tubes up on this one side we'll just focus on one side for now so what happens is when this is lifted above ground it's basically putting this at a point to where the tube isn't completely off and it's not nowhere being completely on it's just at a comfortable point if you want to look at it again in a mechanical term you can kind of look at it like a stall converter in a in a and a race car or something like that so when you're at the line on a racetrack you bring your car up to its stall it's at that point to where the car is not idling and you're not giving it full power it's just at that point to where it's ready to go as soon as the tree comes down you can look at it like that if you want and that's what's happening with the tubes it's bringing these tubes to a perfect point to where it's very easy for the tube to transition from the on to the off cycle all right that's basically what's happening it's what bias is for now what's happening is is when this tube receives a pulse what's going to happen is is it's going to try and connect the high voltage here from the plate line it's going to try and connect that to the cathode and what it's going to do is it's going to lift this tube up all right is going to lift it way above ground because this is going to go positive say it's sitting at 8 bolts for example so when this receives a pulse this might take this up to say 25 or 30 volts well when this tube gets lifted to 25 or 30 volts what's going to happen is it's going to bias the signal off so basically the tube is just going to shut right off so it's going to ignore the signal that's coming in to Jack a over here all right when it comes to the transition so when this is basically the the tube shuts off over here this is going to drop down again and it's going to allow this signal to go through so you can see how that's basically gating this signal so you can look at the 6 j7 is somewhat of a mix or tube it's receiving a pulse on the cathode to basically change its level lift its level up and it's shutting this signal on and off and on and off and it's doing that back and forth between these two channels so that we can get to traces on a screen so if we look at the balance control over here what's happening with the balance control is this would have been more accurately labeled as trace position so what's going to happen here is as we move this control here this is bringing V Plus here up here this is a screen set so basically maximum screen voltage only in step this so that you don't give too much screen voltage to the tubes so through this what's happening here is when you move this closer to this side the screen voltage is going to go up on this tube when you increase the screen voltage on the 6j 7 the tube is going to want to conduct more alright so basically what this is doing is this is allowing the tube to be turned on more when the tube is turned on more it's going to pull the plate closer towards ground as it does that it's going to shift the trace on the screen so what's going to happen is basically this is just going to allow us to move traces on the screen why they called it balance is kind of Oh I figure what they've done is because we have a square wave all right so we'll have basically a signal here a signal here and it's going to be doing this and then in order if we have a little bit of signal on the square wave here and here and here and here and here and it's moving around what we're going to want to do is play with our scope settings and make this portion of the square wave larger so it appears as one trace and then we'll do it with the other one as well now what's going to happen is is we have a square wave now if we bring this to the center basically what's going to happen is it's going to balance this out so the basically it's going to look like the two traces become one trace right at the center here and that's maybe why they call it balanced because they balance it out again I would have figured no trace separation would have probably been a better term so that's how this circuit is working and by looking at one channel here we can very clearly see how the other channel is going to work when this one's on this one's off when this one's on this one's off and it's just going to be doing this back and forth and that's how we're going to get our dual traces on the screen that's basically how this circuit works now at this point I just drew this thing up I don't have any voltages because hamp part of the thing up yet and it needs to go through the rest oh so I don't know any plate voltages I don't know any any screen voltages or anything like that but I'll edit those in later on here's another thing this is a DC coupled circuit alright but since this is a DC coupled circuit we have the plate connection here this can be high-voltage on this and you look at that it goes right to the output jack there's no blocking capacitor no blocking capacitor at all why have they done this basically just to keep the integrity of a square wave signal so everything is DC coupled right into the circuit you'll notice that there's no blocking capacitors the only blocking capacitor you're going to see is between the oscillator and these two cathode followers over here alright so basically these are just acting as two large switches so we should have some you know a nice square wave going into this thing and making a nice trace and that's really what it is so at this output Jack I have to remember to be very careful or I might zap myself there's a there on login and output I don't want to touch both of those at the same time and I'll measure these in the end you'll see what I mean you can see the high voltages here goes through this choke through the 100k we have a 40 mic capacitor here acting is more filtering right through this 47 K resistor right to the out so a high voltage rate on the output jack so if you ever find some form of a DC switch like this this is something to keep in mind again they're doing this to keep the integrity of that square wave and we'll take a look at square waves to see how well this does again this is a low frequency device so this thing is going to be very good with low frequency square I imagine if we start you know you know pumping fast square ways and Irian which is dealing with twisted-pair right we're going to probably get you know sawtooth locking square waves but you know at lower audio frequencies it should be okay so nonetheless it's going to be fun to bring this thing back to life and use this in some future episodes so that's it you know five by four full wave rectifier here so you can see Center tap here this goes to ground high voltage on this plate in this plate and then we have our filament winding here heating the tube extender top of the filament winding comes out goes into this filter reactor we have a 2 micro farad capacitor on this side feeling a little bit of smoothing you don't want to put too much capacitance right here because then this thing is just going to look like a resistor it's not going to be a reactor anymore so we only have 2 micro farad here which is allowing a lot of filtering to be done over here and we have two a 40 here and a 40 here so what else can I tell you here it's pretty much it filament winding Joule light here that's a little green light on the face and this just runs to the heaters I don't draw the heaters on here just because don't really don't need to show one end of the heater goes to ground the other end just goes to here again you know just keeping complexity out of the circuit that doesn't need to be there you'll notice that I did draw this the suppressor grid on this one tube here and that's because it has an external connection so it actually comes out of pin 5 so I've connected it to pin 8 like it is there again this is an internal connection in this tube so I just drew this as a as a tetrode and that's pretty much yet what else can I tell you this selects the range this would be the slowest range this fastest arrange point zero one being slow these are gang together and they move like this all right so you can see that it matches on both sides and this would be the define two nor the the trim between them so there's two four Meg potentiometers here gained together acting as the as that in between frequency control I'll explain why I think that this thing was most likely a factory recall or some form of a warranty that might have even gone back a couple of times so if you recall when we first took the unit apart and we looked on the underside of the chassis here you probably noticed that they had a little bit of ink felt marker on every single solder connection and when I first looked at that I just thought you know wow that's some pretty good quality control and really didn't give it a second thought because it's everywhere every single lug on the tube sockets everything has got these this felt marking on it you can see it it's it's everywhere even the solder joints here everywhere that there's a solder joint there is a little bit of felt now when I started taking everything apart here and removing the parts and pieces I found out that this particular capacitor was not even soldered there is no solder on this whatsoever where it hooks onto the tube socket down here so chances are one of the channels in this unit was very intermittent and caused this thing to go back to the factory a bunch of times until it got to the point where somebody said check every single connection and mark it and that's what they did in this unit and you can kind of see their thought process one channel being intermittent where might the problem be so if we look on the top side of the chassis here a bunch of solder rules supporting this thing so that it'll sit square on the camera so if you look on the top side of the chassis here this is the channel that would have been acting up you can see they've marked all of the wires here as well you'll notice that this is the potentiometer that they've changed so you can see this here one here looks quite a bit different than this one here this looks like the case of this looks much like this here and the other potentiometer on the bottom even mark the solder connection on the you know that grid cap of the tube here so very good possibility that this thing was a real troublemaker and that would explain why this has such low time on it probably because it was acting up and that would explain what all the original tubes are still in the chassis here now as I was doing this and taking the measurements for the schematic here I removed the wires off of this because I couldn't get a very good measurement this here is the same potentiometer as the one underneath the chassis so when I tried to measure this I just got funny readings and nothing was really happening and I'm thinking that you know maybe there's something else in the circuit maybe some capacitor or something that's causing some issues this is really before I started going after the schematic all the way rate is about mid schematic I did this here so I measured this and this potentiometer is completely open on both sides here so I can go over to one side here like till about this point here and it starts to make connection right I have a you know few K ohm here down at the bottom and then it opens completely to here and then again on this side it has you know a couple of K ohms down to this side so there's a whole bunch of wire here that's completely disconnected and it's done it on both sides so why it has you know basically blown almost evenly on both sides is really bizarre now there are capacitors here what's happening is this here ties directly to the screen grids of the of the six three seven sir so we'll take a look at the schematic again and you can see here that you know the screen grids they've got these capacitors these four micro farad capacitors right to ground and that's on either end here so maybe what has happened is these capacitors have become very leaky that would be these two capacitors here this one right here and this one right here maybe they became leaky and it just eventually destroyed this so you know yet to be found out so very interesting so this thing really does tell quite a story that might actually be the reason that this thing has this tag on it who knows how old this is you know what says okay on one side and it's written in red writing them and see that kind of gallery' this is okay there so maybe this thing really never was okay it was just a continual troublemaker at least that's what it's looking like so anyways back to this potentiometer here this is on the backside here it says m70 MP right here m70 MP so if we look on the bottom here take a look at this one here there's another potentiometer here so if they look at this one this one is the same and it measures 70 K with the potentiometer wide-open they've tied two ends of it here together just because of you know they have this controlling the level of the screens so what I'm going to do is I'll replace this one here with something suitable under the chassis and I'll put this one here on the top side of the chassis and I'll replace that screen control up here or the balance control for the screens I should say I replace that middle keep the upper portion of the chassis looking on right now as I was on the upper portion of the chassis I'm measuring this one and this one and they both are supposed to be 100 K ohms they say on right on the actual case here but this is supposed to be a hundred K ohms but it measures 70 now you're probably saying well I'm going to disconnect some of the wires well this just runs us to an open jack so from an to n 70 K and 100 K over here so what I've done is you have got them around here somewhere right over here I've got two brand-spanking-new 100 K ohm potentiometers and what I'm going to do is just put two brand new ones in here the shaft length might be a little bit long so I might need to take a little bit of the shaft length off is kind of a universal fix this one here these are nice and smooth and brand-spankin'-new just have a bit of solder on them here because I've used them for for breadboard testing but um so I'll end up replacing easier as well so have a nice matched set of 100k potentiometers here and when I'm putting this other one in here I'm going to do is carefully measure each side here so each side from the center and when I get exactly the same calum reading here you know this is 70 km but they're never really 70 K ohm so you know just for example say this was an e DK on potentiometer I would want to read 40 K from this side to this side and 40 K from this side to this side and that would mean that this is roughly you know right in the center so when I have this this potentiometer here centered the new one centered what I'll do is I'll put this right in the center and you'll also be a very good indication of how well balanced everything is in this circuit when it's put back together at this point I'd say I'm about halfway through the restoration now I would love to have you guys with me through the entire restoration just have the camera rolling as I'm testing and replacing components and removing things and verifying parts and things but I would have hours and hours of footage just a night alone through the magic of a camera you know this seems like seconds between each shot but actually to get to this point was quite a bit of time so at this point again about halfway through now on the top portion of the chassis here I've removed both of the game potentiometers here and I've also shortened the shaft on the new ones I haven't installed them yet because I'm going to clean the face here first with a mild detergent so I'll remove these chickenhead knobs here I'll leave the binding posts on and everything else here but I'll remove the chickenhead knobs and I'll clean this up this should come up really nice you can see the tested here somebody's put on is a little clearer than before there's out writing there's no writing on the top rim here there's the B and over here is that 1/16 stamped there so so this should clean up pretty nice now on the backside here I've also removed the potentiometer from the bottom and I've installed it here so this is the one from the bottom portion of the chassis the original one is right here and it is quite faulty so if we look at the potentiometer here the first opening is there is two little dots there's the first one the second one there is where it's open on this one side and if we look at the other side there is a line there's the line right there it was open right on that line so odd you know even area from each side and then this whole area of wire in the top here is just you know completely disconnected now for those of you that have never seen inside of a wire wound potentiometer this is what it looks like so what happens here is where the lead goes in there's wire that's wound around a form all the way around here the wire is very fine like a hair and it goes all the way around from one side to the other this is the wiper that's connected to the shaft and the shaft is insulated from this particular part here you can actually see the insulator material here so when this is down at this point here there is really low resistance between these two pins right here as you start to move the wiper up this is rubbing along that wire here as you get further and further from this pin right here the resistance is climbing in climbing climbing until you get to the extreme end here now what happens with these things is when a capacitor leaks or something like that usually what it does is it just burns the wire up and that's what it's done right over here and read it that little second dot right there it's put to little burn marks there now this really isn't repairable unless you want to spend a lot of time in here again I couldn't even begin to imagine the turns count of wire in here so you see that it's really even too fine too nice to see any definition of a wire there but at any rate lots and lots of turns here so on something like this is bad you just go about replacing it what I do is I usually throw these things in a bin if I ever need parts down the road I can get this shaft off here by removing this little clip and the center piece will come out there's spare parts and pieces so if I have another one of these things that does have an issue that doesn't involve this wire being open I still will have some spare parts and you know I've thrown lots of this stuff away in the past and you know I've you know pretty much kicked myself later on for not keeping it so this is what I do I just put this in a in a dead parts bin and no market as being open in two areas here so anyways that's how a wire wound potentiometer works so if you ever want to test one of these things or pretty much any potentiometer if you want to see if it's good usually what happens when a potentiometer fails is it opens somewhere along the resistive track so all you do is you disconnect the potentiometer and just measure with your own meter from end to end if you get a resistance this one here would be 70 K ohms you're close to I know that the wire is still making connection for a man to end and then the next thing you do is you go from one end so you bring this down here like so put your own meter across it like this you should have close to a dead short at this point and then slowly advance the control while watching your own meter and it should slowly climb as you turn this and then when you get to this end here you should be rate at 70 K ohms when you're measuring this side and it's the same with this side this side would now measure a dead short because the wipers at this side so as you move it this way this will slowly climb the resistance between these two pins all the way up to 70 K ohms at this end here and that's how you test one of these potentiometers are pretty much any potential endure for that matter so on the bottom portion of the chassis here grab a solder roll here to support this we go so what about a portion I've replaced these capacitors here which were these ones here so these are the new ones here and they kind of actually fit right into that little slot there so it gets rid of these ones these are the new electrolytic capacitors mounted here so that replaces those two large cams on the upper portion of the chassis this potentiometer here replaces that one that I've now taken from here and put it onto the top in fact this particular potentiometer is a pretty special one I've got a bag full of them but it fits the bill it's basically two potentiometers controlled by one shaft so you can go from n to end and then it kind of hits a stop and then there's a fine tune at the stop and then if you go the other way right to the other end and you'll hit a stop and then there's a fine tune from that point so it's a really neat potentiometer again I had a bag full of these things and it fits the bill you know it's about the right watch about three watts worth right there this capacitor here this two mic capacitor has been replaced with this - mic capacitor and all the sealed tight capacitors these guys solar sealed tight you can see wax molded paper so this is a paper and foil type capacitor you can see here it says outside foil so I've mentioned paper and foil in many of my other videos and people say don't you mean paper and oil no these are paper and foil capacitor and in fact most of the capacitors from way back when are like that so at any rate bad capacitors very leaky again sealed tight to keep the leakage in those are out of there replaced by these guys right here near style capacitors of the correct value now this capacitor here was at point zero zero five micro farad capacitor a modern value that would replace that would be point zero zero four seven that's going to be just fine no big deals there they use a lot of different values in here that can be you know replaced by a very close value I've replaced the electrolytic here and here the reason that they have heat shrink tubing on them is because they've been repurposed from an extremely high voltage power supply that I built some time back that I'm no longer needing to use anymore capacitors are all good so I just used them so I didn't need to take a trip into town to go any by any of these capacitors here so those are replaced there what else can I tell you under here haven't used any contact cleaner yet I plan on doing that still need to put in the line cord everything on the bottom portion of the chassis at this point is pretty much done aside from contact cleaner and line cord so all I really need to do is clean the face up at this point and put those potentiometers back in I'll clean up the chassis clean up the case and at that point when I'm ready to power this thing up we'll do that together and hopefully this thing won't make any smoke and I think that's about all I can tell you right now haven't bothered testing the tubes I'll just use the circuit itself to test the tubes so a lot of the times the best test for any vacuum tube is the circuit it lives in and this is very true for most tubes so what I did to this in order to make this come out this incredibly shiny is first of all I took some 91% alcohol and I went over this with a liberal pressure a whole bunch of times really just to clean the surface and open up the pores of the paint and then what I did is I took some swirl remover and went over this a few times with this swirl remover here and then after I was done I used some wax this is just automotive wax and put this on the top and buffed it out and that's how it came out now the alcohol step for this was very very important and the removal of the face also was very important if there's will not still applied to the face here when you try and polish it you're always going to have that little rim of dirt around there and you can always see that and that was really what made it necessary to remove this space to clean it this well but as you can see it turned out very very nice and it's got quite a shine to it here can almost see myself in it so that's how we clean the face of this now if you're working on older test gear pretty much every different piece will react differently to different chemicals and you need to be very careful always test everything you're going to do in a little inconspicuous area first before you go just you know taking everything and putting everything right into it you know for example say this was a different kind of paint alcohol might try to remove this right so again you got to be very careful and of course for each different piece of test gear you know there's a little bit of a different process it just takes a little bit of experimenting on the face or in an inconspicuous area where there is some pink and before you know it you'll be well into cleaning it up the electronics which is pretty much finished at this point the only thing I need to do now is install a brand-new line cord and we can try the thing out see how well it works the thing really went back together quite easy they really did their measurements well the face on this thing is held on by these two screws and the binding posts at the bottom have long shafts on them that are threaded and you just put a nut on the backside so the grounds are just chassis ground really and that's what holds a face on these two screws and these two binding posts on the bottom so to give you an example I just basically lay the face back on tighten these two screws up and the two holes for each binding post perfectly lined up they just fell right in so they did a really nice job with their measurements on this thing here everything else is just kind of fastened to the face same with a light null the controls on the top here I installed two brand new potentiometers here and I'll show you those in just a moment one thing to keep in mind whenever you're putting the knobs back on a potentiometer with a non-indexed shaft so when I say non-indexed shaft I'm talking about a potentiometer like this with it just basically looks like a piece of round stock there is no flat area so this is non-indexed so you can pretty much install these things in any position you want and then just align the knob and then tighten the setscrew onto it so that it points to the appropriate area so when you put the knob back on you turn the potentiometer down to zero put the knob at zero if you tighten up the set screw what's going to end up happening is is it's going to move the shaft on the potentiometer so what's actually happening here is it's acting like a gear set as you're tightening up that little set screw so you have to offset the knob just a little bit and then when you figure out exactly how much it's turning that shaft it'll go right to zero when you put this right back down again and that's what happens here so it does make things a little bit time-consuming doing that you could say well why don't you just turn it the other way and you know it'll pretty much hold it there well as you can see these potentiometers go past 100 at this point here whereas they sit at zero even the factory one on the bottom on the frequency control doesn't go exactly rate to 100 so it just depends on the potentiometers that they originally designed this thing with these are very close like you mean there's just a little over 100 so these worked out very nicely so something to keep in mind whenever you're dealing with a potentiometer and a non index shop I'm going to show you something else that's a very good idea here in a moment as well something to keep in mind for any of your future builds so what I'll do is I'll move the chassis around here we'll take a look at the backside and I'll explain exactly what I've done the chassis cleaned up very nicely as well I used a mild metal polish basically just to take off the oxidization here and to clean off the surface cred that's just settled on the chassis over the years the side of the unit here has some slight pitting on it I'm really not too concerned about that it is really quite mild now it's always a very good idea whenever you're cleaning a chassis like this so you're going to use a metal polish to try that in an inconspicuous area as well you'll notice that there's some stamps on the chassis here that marked the tube numbers so this identifies what goes in the socket some metal polishes will remove inks very easily so the stuff that I have is extremely mild now I could have polished the chassis to a mere finish but I really don't want to do that because didn't look like that when it came from the factory and not only that if I do spend that kind of time polishing these numbers are definitely going to go missing so basically just clean the thing up make it look like it did when it came out of the factory that's good enough also took the time to clean up the tube shields here as well now you'll notice that I've installed the two new potentiometers one here and one over here and you'll notice that the wire side is down now on the other ones the wire side was up now when you're dealing with a non indexed shaft as mentioned earlier you can mount the potentiometer any old way now the reason that I've done this is because there's an opening in the top of these potentiometers and you'll find a lot of potentiometers or like that so if we look right here you'll see that right here is that open in the topside now that opening will allow dust inside the potentiometer over time dust will settle inside so by repositioning this and having this on the bottom side really slow that process down now you might say to yourself well the thing is pretty much a sealed unit well no there are holes in the thing to breathe on the bottom side of the cabinet or on the case there are some large round holes and that will allow convection cooling to occur within the chassis here now convection cooling is used in a lot of vacuum tube equipment you know no need for fans or anything like that and it really used to oversize the Transformers so that they wouldn't get hot and especially in a device that's going to be used in an industrial application they don't want the thing to go down it needs to be very dependable so what happens is is you see that there's holes in the chassis here heat from the tube Rises and pulls cold air through the bottom portion of the chassis and it pulls it up through the round holes or something a pretty large round holes in the bottom of the case so by having this convection cooling it allows the components on the bottom side of the chassis to cool and it also will draw air up past the tubes and things like that well whenever you have airflow even from convection cooling it's going to impose a dust issue and the dust will circulate in here and then settle on the components and that's why when I open this thing up it was full of dust just from that convection cooling process so if you ever have the option to put in a potentiometer face down like this it's always a better idea you know there's always dust and it will always try to get inside but at least you know when the dust settles it won't be settling on the carbon track and you don't end up with a scratchy potentiometer for the first power up I have this thing attached to my current limited power supply over here so as a very act isolation transformer and basically dim bulb tester all in one those bulbs are acting as current limiting so I don't know the state of the power transformer and this unit I imagine it's okay because that one amp is fine it looks like there's really no time on this thing but what I'll do is I'll just turn this on and then on the bulbs here they should light a dimly and they are so that's how it normally looks so it'll do is I'll turn the unit on now I'll just - just the lamp off here here we go and they're just a little bit brighter which is normal now the thing to watch for is if there is a problem in the high voltage section when the rectifier tube here warms up you can tell it's warm by those two little orange glowing strips at the top of the tube right here and here so if there was a problem in there and those are glowing orange these light bulbs would be so incredibly bright right now it would be washing of the camera they would be lit up to full brightness and they're just barely glowing now the camera itself makes those bulbs look brighter just the way it is because the camera sensitive to that so everything is fine so the next stop would be to take this thing out of current limit so just basically flip this switch over here and that bypasses the bulbs and then I'll have a full 120 on this unit here and I'll do that when I have the oscilloscope hooked up and we'll see what this thing does on the scope I figured the proper way to display this older electronic switch would be to have it hooked up to an older oscilloscope this is a known single trace of Silla scope in fact I did a restoration on this oscilloscope not long ago if you look in my videos list you'll find the heat kit OH - 11 restoration so I've got this hooked up to the scope through twisted pair only just like it was intended way back when what I'll do first is I'll turn on the oscilloscope and we'll let the oscilloscope warm up and then after this is all warmed up and set then we'll go after this thing and turn it on and get everything set up I've put some wires into the binding post here so I can just clip alligator clips on I have my signal generator or my audio generator hooked up right now and I have around 100 agonal or something like that coming out of the test leads that's ready to go as well and the amplitudes about 50% so that should be okay all right so we'll turn up the intensity here and there it is so I can see the scope really hasn't been moved since last time which is quite a while ago this is also going to sit on that other bench that I've got going the restoration bench all right so what I'll do now is I'll click on the power supply to the electronic switch so it's still hooked up to that variac supply and it's just through right now there's no current limit so here we go and we'll see what happens I hooked this up first because I know there's high voltage on that jack and I don't want to touch it and we have life of some sort happening here it looks like two traces already can it get any better let's see just let it warm for a second looks like they're kind of drifting together a bit all right so I'll move the balance control so it is setting at zero we'll see if I can yeah there it is go right together and that's pointing rate at zero so those tubes have got to be very well matched ah you know again I say that this thing has probably got almost zero time on it so when I move the balance control it should shift the traces and as you can see that's exactly what it's doing so I can even swap them if I want okay so there we have it so what I'll do now is I'll grab my tables and suppose down here grab my cables and I'll feed an audio signal into this thing so the common lead to ground and I'll just attach this to input a first start with input a gain a I'll turn gain a up and look at that well I have this looks like it's on a square wave here I'll just turn it to assign a there we go so there's a sign and as you can see it is not going to lock so I'm going to need to give this a sync signal so I'll have to sync the scope to the input a so I'll just grab an alligator clip over here probably should have been a little bit better prepared I wasn't expecting this thing to come to life like this this quick so here we go put this on to sync now there's no high voltage on these so I'm fine at this end here I'll just clip this and this should lock the trace hopefully and there it is so trace a looking good so let's see if we get anything on B see how B works so what I'll do is I'll just bridge with another alligator clip which I've got right here I'll just clip this to be so I mean it's just going to feed the same signal from A to B hope this from here to here now when I turn up B I should have the same sine wave on and there it is look at that my Heathkit Oh - eleven dual-trace oscilloscopes working very well it's locked and everything it's just wow that easy what a nice device I'm looking forward to putting this thing on to the other restoration bench and again that bench is you know still being made and do some tests with this older electronics which maybe align some equipment with it so what I'll do now is I'll put it back to square wave let's see what the square waves look like so here we go it's actually surprisingly well look at that looks very well what you're seeing here is this locking the oscillator is going to be trying to move here I can probably demonstrate that because we're dealing with square waves and another square wave and then the square wave that's separating the traces here and you can see this is extending to the top then that's a dead giveaway that it's the other square wave because it has to go from bottom to top to make this so what I'll do is if I move the frequency control I might be able to slow this down on one side and you can actually see the action there it is so you can see this I'll just trying to gain down that square wave that you see right there is the square wave coming out of that 7m7 tube and if you want to see the mixing action all I need to do is turn up gain a and you'll see a square wave imposed on that particular portion and this will be the square wave from the signal generator so I'll turn this up and there it is you can see it mixing now if I turn up game B the other signal will appear down here now if I just move this a little bit I can get that to move across the screen a little faster so you can see about that's happening so if I speed this up a lot it will look like two traces there you go now you'll know stuff is a bit of an artifact happening in here and that's because of the switching I'm not really too worried about that I could probably get rid of this little bump on the top probably with some capacitance adjustment in the circuit but again I'm really not worried about it it's you know just kind of a neat old device kind of a signature of the older device so what I'll do is I'll just try and slow that particular movement down and if I get this right in the right spot I imagine I can probably there we go that's basically with just one moving across the screen and I can stop that almost so not a big deal you know having that little thing move across here every now and then and if I wanted to get used to the artifact I could just have it really quick moving and then of course we get to that one spot where it stops so you can really see how this thing works and it works very well and surprisingly look at how square these square waves are for a twisted pair amazing they did a really good job designing this device just move this around a little bit and it'll be like this in the other ranges as well if I wanted to use a slower signal I would just change the range switch here and and I would imagine slower signals probably have even a nicer looking square wave but look at that it's you know a really nice looking wave so I'll get the sine waves back here again and I'll just display that again with the sine waves so put this on here like so and I'll move this so we can see the square wave doing its thing so you can see the top portion and the bottom portion this is our lower trace and our upper trace and if I shut the bottom one off you see the square and if I shut the top one off you'll see that the actual oscillator move across the screen turning up a will mix the sine wave into that and as you can see it's doing that and if I turn up B it'll mix the sine wave onto the bottom portion so you can see how that's creating the two separate signals and then if I speed it up then it looks like just a normal dual-trace oscilloscopes and with a fine adjustment here again you can really slow down that artifact so it's really not a big deal very impressive very simple to use as well and again of course if we you know take the sync control off you know there'd be just no locking this at all so very important to have an external sync input in order to use something like this so all in all big thumbs up for that device that's working really well I'm looking forward to doing some future experiments with this thing and aligning some gear with you guys thanks for stopping by the lab today hope you enjoyed this episode involving this Sylvania electronic switch if he did you can let me know by giving me a big thumbs up and hang around will be many more episodes coming like this in the future we'll be taking a look at solid state and vacuum tube electronics alike and of course as usual we'll dive right into it and I'll do the explanation and lots and lots of restorations if you haven't subscribed yet you may want to do that as well if you're interested in taking your electronics knowledge to the next level I have an ongoing electronics course on patreon right now so I'll have that link just below this video right about here in the description if you do go there check out the community section so click on the little community tab and there's many people there that have uploaded their projects and we have a build along going along right now so we're building a bunch of projects together so it's a really interesting little area to check out I'd also like to say thank you to all my patrons at this point it's only been a half a year and I'm already just about halfway to my goal the closer I get to my goal the more I can be here on YouTube making videos so really what this is doing is this just to helping me afford the time to be here so I can make videos for you guys so again thanks a lot big thumbs up to all you guys as well so I'll see you next time take care bye for now you

Channel: Mr Carlson's Lab

Views: 207,901

Rating: 4.9268703 out of 5

Keywords: Sylvania type 104, electronic switch, oscilloscope switch, antique oscilloscope, old oscilloscope, test equipment, dual trace adapter, teardown video

Id: ZaOZBmCXjAo

Length: 76min 32sec (4592 seconds)

Published: Wed Jun 28 2017

Reddit Comments

[u/ike_the_strangetamer]

I wish today's VX machines were that simple.