Transformer Repair {Depotting} Lets Look Inside!

hi everyone and welcome to another episode mr. Carlson's lab in a previous video I posed a question to all of you would you like to see me deep pot a transformer and the response to that question was an overwhelming yes so that's what we're going to do in this video together and we're gonna also design a tool to make this de potting process just a little bit easier so there's a lot of interesting stuff coming in this video here so for those of you that haven't seen the previous video if you'd like to watch that just below the description below this video you'll see a little tab that says show more if you click on that show more tab the link to the previous video that led up to this one will be under there you can click on that and if you'd like you can watch that after this video or even before this video whatever makes you happy in short what we're going to be doing in this video for all the newcomers here is the transformer itself in that oscilloscope is filled with tar so what they've done is they've taken a transformer put it inside of a shell filled that shell with tar that shell holds the transformer steady with the tar and the tar also acts as a little bit of an insulator well what they also did is they potted a capacitor inside there in that capacitor has gone faulty and that poses a shock hazard on the case of the oscilloscope because it's basically running from the line cord to the case of the scope so we need to get rid of that capacitor in order to do that we need to depart this transformer which means that we have to melt the tar in the case of this transformer and pull the actual transformer out of the case so it's a little bit of our process and we're gonna have to design a tool to do this that will make that process just a little bit easier now here's the thing this transformer is from the late 30s era and by heating this thing up hot enough to try and melt this tar might also damage the transformer itself not a big deal the oscilloscope will work again no matter what I have lots and lots of transformers I can fit another one even hide it inside that old shell not a big deal we're gonna do this in the name of science so whether the transformer lives or whether it doesn't not a big deal we're gonna find those capacitors and we'll take a look at what they've actually done in there and how they've potted this thing what a silly thing to do put a capacitor in there with ATAR so that's what's gonna be in this episode here so what I'm going to do is get some stuff on the bench behind me here and we're going to get started in designing that tool that's going to make this just a little bit easier I remove the transformer from the oscilloscope and it really came out with ease four screws four nuts and removing the four standoffs just D solder the wires and of the transformer comes so about ten minutes worth of disassembly there including taking the entire scope apart and desoldering the wires now you might be saying to yourself look the wires are all the same color this thing's gonna be a total pain to put back together well not really there's a bunch of ways that you can do this you can Oh out the windings that's a a little bit of a time-consuming process but it works quite well if you're unfamiliar with doing that I'm going to show you guys how to do this here in the near future we'll take some random transformers and I'll just emotes um windings and we'll draw a transformer on a piece of paper and I'll show you how to figure out what the transformer does so that'll be coming in the near future here a very easy way of marking things is get a bunch of markers just like this and what you do is when you do solder the windings from wherever they are in the oscilloscope you can color code the solder just by taking a felt marker and rubbing some of the felt marker on the solder it really shows up quite nice on that shiny surface so you can see I've got two red wires here and if I go over here you can see that this one's blue so that's blue and then I've got some green ones marked over here you can see that's green now that all corresponds to what I've marked on the schematic for the windings so you can see I've got red red here this is a multicolored one there's green and blue so I've put two stripes on the solder for this and this is just solid blue and green and green and then I have two marked block and black that go across the switch it just is that easy now if the transformer works like this one does it would be a very good idea to take voltage readings before you want to depart your transformer because if we depart this thing there is a chance that heating that tar up hot enough to the tar might actually damage the windings if it does we want to know how to replace this transformer very easily so taking some voltage readings off the windings when this thing is on just before you remove the transformer is a very smart thing to do so you can see that I've got 146 volts AC at this tap here from ground or chassis this is the tap that runs up to the sweep here at the top end here this is high voltage winding here we have two 402 volts ac and I have two leads up here that are red in red which are the filament windings for the 6x5 no we really don't need to read the voltage across that because they're attached to a 6x5 the first number in the vacuum tube is the filament voltage so it's six point three volts so we know that these are going to be roughly six point three volts don't need to read that and same thing with a nine thirteen we have two green wires that run to the filaments of the nine thirteen not an issue there you can see that these two wires are black that come out of the transformer and that's because one of the wires that runs into the transformer comes right back out from the outlet again kind of bizarre why they did that anyways these two just runs straight up to the switch and it just makes things that much easier to figure out now these capacitors are nowhere in the oscilloscope so the most logical place for those things to be is inside this transformer now I've had a bunch of people say to me I'll just get this out of the way here I've had a bunch of people say to me Paul you know I don't think national would put the capacitors in the transformer that really does sound like a crazy thing to do well now that the transformer is completely out of the oscilloscope there's no connection to anything let's see if we can find a capacitor inside this transformer just by looking at these open windings I've also had some people say that maybe it's just leakage between windings well let's look for that as well before we depart this transformer because if those people are right in there are no capacitors hiding inside this transformer we're gonna deep pot this thing and risk this transformer for nothing now in the name of science we're gonna do this thing anyways we're gonna heat this thing up until that tar is nice and soft are gonna pull it all out but you know for for the sake of actually knowing if the caps are in here let's just do a few quick tests and find that out the first test that I'm going to perform is a leakage resistance test from the windings of the transformer to the case of the transformer and in order to perform this test I'm going to use this extremely sensitive leakage tester so what I'm going to do is take the positive lead of the leakage tester and attach it to the case of the transformer I'll turn on the leakage tester now the primary winding of this transformer basically one of the leads just runs right in and right out one of these leads and then back into the transformer again so what I'm going to do is basically turn the switch on so I'll just short these two leads here so this is acting like the switch is closed on the front of the oscilloscope and by doing that it attaches both of these leads to the primary winding so I don't really have to figure out which one is open and which one runs to the winding so there's such low resistance between these two leads here that I only need to attach the leakage tester just to one of these leads again we're looking for leakage from the winding to the case so I'll take the sense lead here and attach it to the primary winding and as you can see virtually nothing there nothing whatsoever so what I'm going to do is remove this and we'll test from the case to the high voltage winding here so I'll click this on to the high voltage winding and as you can see just a little bit of capacitance nothing there now if we look here on the schematic you can see I have red red and this is marked green and blue and blue you can see that these are all attached to one winding so we only need to attach the sense Lea to one of these wires because this winding is a very low resistance all the way across so to this machine here this just looks like a dead short all the way across so we only need to choose one of these wires and we've just chosen one of the red so we've completely tested this entire winding for leakage to the actual case right now by just choosing one wire same thing with this because this is such a low resistance here we only need to choose one green wire so we'll do that this here looks like a green wire it is you can see the green marking there no problems so as you can see virtually no leakage to the case of the transformer at all now let's test from winding to winding to see if there's any leakage so we'll test from the primary winding to the filament winding for the nine thirteen so I'll attach this remove both these leads I'll attach the positive lead to the primary winding and we can see that these are green marked green so I'll attach this to one of the green leads here and as you can see a little bit of capacitance there not too bad and as you can see passes a leakage test not a big deal now let's see now this is where it's gonna get tricky so here's the thing we've now tested for leakage between the case of the transformer so you can see that we have a shield in here we've tested for leakage between the case of the transformer and the windings here now if we have capacitors hiding inside the tar of this transformer so if one of these capacitors is hiding inside here you can see that the capacitors both go to a ground now we know that that ground is not the case of the transformer because we've tested from the primary to the case and we see virtually no leakage where are they going to attach this the most sensible place to attach these capacitors would be to this ground right here so to the blue mark the lead running out because that attaches to the shield you can see it attaches to a dotted line inside the transformer so that basically is the ground for this winding here and the shield in the transformer so I should say the common for this winding here so this is where it's going to get tricky so what we're going to do is test from the primary to any of these wires on this winding here and because this is attached of course to the shield and all of these we can choose any of these wires again so we're to the primary here right now we're testing to this and as you can see the linkage is nil from this winding so let's move to this winding here look at that it's looking pretty excessive to me now this is where it gets tricky in order to determine whether this is leakage from winding to winding or whether this is a leaky capacitor inside we need to use a capacitor tester we need to look for basically capacitance if this is leaking from winding to winding this is just gonna look like high resistance with you know almost no capacitance whatsoever if there is a capacitor inside here and it's leaking it will show as a capacitor with resistance so right now we're seeing the resistance all right so this is showing quite a bit of leakage now what we want to do is look for that capacitor and see if it actually is a capacitor hiding inside there there are many many different tests for capacitors the leakage test is just one of them so this is a leakage tester so this is looking for a leakage resistance we have ESR testing we can test for capacitance there's all sorts of different types of tests that we can do on capacitors it just goes on and on and on again this is just leakage not ESR or anything like that so what I'm going to do now is remove this tester here I'll just get this all out of the way and I'll go get a capacitor tester and we'll see if we can locate a capacitor inside let's look for a capacitor in the transformer with this capacitor tester no so I'll attach one of the leads from my cap tester here to the primary and we'll go directly to the ground so that's the shortest path for this capacitor here and as you can see it's confusing this new meter this isn't all that uncommon so what I'll do is I'll reverse the leads and see if we can get a reading this way and because we have windings in the transformer the meter does not know what to do again quite common so what I'm going to do is disconnect this meter here move this out of the way and connect up my trusty old Tektronix tx3 this thing is an ancient meter and it works awesome never giving me an ounce or grief this thing here we go it's on capacitance already see what happens 40 nano so we're looking at point zero 4 micro farad that definitely is no resistance and windings so there is a capacitor in there somewhere hiding in amongst the goop point 0 4 micro farad and again that's between the primary here and the bottom of the low voltage winding here so I'm just in between one of these leads the switch is closed right now so any of these leads and this lead right here that would make sense because we have two grounds here they're gonna be connecting these two together point 0 4 is hiding in there so what is the reading on the schematic here so it says point 0 1 so point 0 1 and the leakage you know that would show up as a point 0 4 so there we have it yes national did hide capacitors in the tar so let's see if we can dig them out or melt them out or whatever so in order to get the bottom of this transformer off what I'm going to do is just break these barometz as you can see they're just pretty much break right off you can see that how crusty those things are like that so I've seen them a lot worse they're like glass these are just a little bit of flex in these things still kind of gummy I would say get these out of here like so that one's like glass just breaks off this one will be the same no not too bad a little bit gummy all right so I'll lift the bottom of this off now I can wiggle this out some of these grommets are still a little bit stuck there look at that big tar filled mess there look at that on this side you can see that just horrible mess so this thing is just filled with this horrible sticky substance so the next step to do would be to make a tool to soften this thing up so that we can just remove the transformer it doesn't look like the actual core of the transformer is too tight what I'll do is I will zoom on in here just a bit and you can see that it doesn't look like it's that incredibly tight against the case so it looks like they have some piece of cardboard or something in there kind of wedging it so probably to hold it so that it maybe doesn't buzz or something you see a little bit on this side but it's not you know like pressed in if it was that'd be horrible to try and pull this thing out so what I'll probably end up doing is heating this thing up very very hot and then this tar will end up melting and then maybe by just holding the leads and pulling up we can remove this out of here might have to try a bunch of different things so you never know that even the capacitor might be just give this crap out of the way here might even be hiding just stuffed right down in there again there's a lot of tar in this thing so they may have put that way down in there leads are pretty stuck you can see some tape here I'd be factory tape that they've joined to the windings here so I bet you the actual capacitors are probably sitting down in here something like that or maybe even on the other side here who knows at this point yep this is going to get messy in order to melt the tar in this transformer I think you're probably the easiest way to do this would be to use a toaster oven so here's my plan I'll get this thing out of the way move this over here so I went to a thrift store picked up this hideous looking toaster oven and it's it's pretty ugly so I can back this out here just a little bit you can see this thing is pretty ugly I got it for a look at seeing us crumbs and it's still the handles broken off and everything but here's the thing the elements work and there's two elements on the top as well so here's my plan since this has a temperature control here you know there's temperature control for the lower elements and for the upper elements what I'm going to do is take the transformer and between the two upper elements what I'm going to do is cut a square hole here and I'm going to put the transformer down inside that hole and I can adjust the temperature in the oven to bring this up to the point to where the the tar just melts so I don't need to put on the upper elements I can only use the lower elements and it'll get nice and warm so I won't really overheat the transformer and I'll be able to pull this thing out quite comfortably so what I'll do is I'll trace around the transformer here I'll cut a hole in the top of the oven and then what I'm going to do is screw this down to the top of the oven as well and that way when I want to lift the insides out I have the weight of the oven also helping hold the transformer in I think it should work out really good so let's give it a shot and see how well it does work the transformer is now mounted in the top side of the oven and how it got the hole so nice and square is I just used the bottom plate off the transformer and traced around this here and use that to mount the transformer just basically drew around this centered it in the center of the oven made sure that it was between the elements somewhere and that worked out quite well now in an oven like this this is the the top of the case inside there's another heat shield to stop the top of the case from getting extremely hot and I just used an air cutoff tool for that inside that's a really rough cut so I did this first one with a dremel and it made a nice clean cut around here and I wasn't too worried about the inside of the oven as you can see and there it's looking pretty rough so I wanted to cut the hole on the inside just a little bit bigger so the heat would travel up the side of the transformer so that it would heat this just a little bit better and that's why this is so much larger around the transformer as you can see it's somewhat centered between the two elements there now I don't plan on using these elements I don't want these elements to come on I just want to use the bottom elements I'll play with the controls on the front here to make sure that only the elements on the bottom come on if these ones come on there you know they're a ways away from the transformer I can maybe almost fit two fingers between the element and the transformer but that's gonna really create a hot spot on the side here and I don't want to do that so I want this to be a slow process so you know there's a good chance that we might be able to save this transformer so this is almost ready to go now another thing that I did notice about this transformer here is they've put a cardboard shield all the way around the entire inside and they filled the tar on the inside of the cardboard so it is pretty stuck in there I used a two screwdrivers and I tried to lift this out and it won't lift out you can see the layer of tar here I'll just zoom on in so you can see that there's that cardboard kind of isolating the entire transformer that's also what's creating isolation between the core and the case here you can see that they very carefully poured the tar within that cardboard shield now I don't know on the top side whether the cardboard is open or not I imagine it's probably covered but also I imagine some tar has gone on the inside of the transformer here as well again I put a screwdriver on this side and a screwdriver on this side and I try to lift this out and it's it's pretty solid in there so softening up the tar will definitely make this easier to come out even if this is a little cardboard box so that they've put this thing in who knows they may have even put some tar on the upside before they put the cardboard box in just to hold everything in nice and tight it is pretty tight in here and as you can see there's a pretty thick layer of tar on here as well and I know if you can see how thick that is so the next step is to heat this thing up and see if we can pull this out so what I'll do is I'll tie all of these wires together like so and I'll use this just to give a slight tug on this I'm not gonna pull too hard because I don't want to pull the wires out of the transformer and if this doesn't work then what I'll do is I'll put two small screwdrivers in here and try and ease this out and if that doesn't work I'll be carving some of the tar away here and I'll see if I can maybe get a plier on the core and pull the core out that way so the wires seems like the easiest way if the tar gets soft this might just pull out nice and easy we'll give that a shot first here I'm in the great outdoors with the oven on a workmate bench I want to do this outdoors because this could get kind of smoky and I don't know what's in this tar if there is you know any kind of a toxic material in this tar I definitely don't want to be inhaling this so it might take a while for this oven to slowly heat up this transformer enough to make the tar soft and melt so what I'm going to do is I'm going to get that process underway I'll let the thing warm here for a while I imagine it's gonna probably take a while and I'm going to want to fiddle with the controls in order to make sure that it doesn't overheat again we want to try and save this transformer right so when the tar is nice and soft and melted and I'm ready to pull this out of here I'll be back okay so this has been on for about 30 seconds and already this is getting extremely hot so what I'm gonna do is just shut the oven off I'm gonna see if I can get this at home look at daddy a little bit of a tug there nice thing about the oven is it'll hold the heat looks like the actual chorus of the transformer itself is there's nothing really holding it together other than that oh here it comes there it is yes and there's definitely some tar down on the bottom there so oh just like this so what I'm gonna do is get this off to the side it is in a nice little box and they did put some tar on the bottom here I'll show you that in just and you can see down in there and see the tar rate at the bottom school corner is filled with car down here very clearly so that's what was really holding the thing in yeah almost no time at all and this came out and this thing is really hot so that worked out extremely well so now back to the lab so here's the transformer out of the case and it's in a nice little box so there really wasn't a whole lot of tar holding this in and even that little puddle at the bottom only made slight contact here so softening the tar up just basically made this soft enough so that the box could just easily come out it's very nice that they didn't pot this directly into that case because if they did I'd had to heat this up quite a bit more and risk really damaging the transformer so really this didn't get all that hot so there's a good chance that we may be able to save this and that's maybe able to so what I'm going to do now is just remove the cardboard box I'll have to make a new cardboard box again I really don't want to heat this thing up more than I have to so the first thing that we're going to experiment with is just getting rid of this box so this bottom piece here just looks like it's a flap like that and here starting to see the actual transformer see that in there so and look what I see all right there and right there so let's just open this up maybe I don't have to completely remove all of this look what we're seeing maybe I can just work this out of the tar and really be careful there you go what are you thinking National like I mean that was just silly there it is right there and that's not enough tubular condenser Wow so what I'm going to do is I'm going to just clip these capacitors out and try and get rid of the leads or just isolate them if I can and then what I can do is work on just repairing these old leads what I'll probably do is just slip some new tubing over the old leads and that way that's a probably the most I should say the least invasive way of working on this transformer now I know that the the line cord wires are pretty short here so what I'm going to do is I'll just get rid of these things we'll take a look at these things here in just a little bit okay that they're even filled with wax so this transformer got really really hot you know like crazy I don't know what they were thinking at any rate so that's what I'm gonna do I'll get the capacitors out and I'll work on either replacing these leads or maybe even just trying to put some new heat shrink on them I'll get this underway and it'll be back here's a question that people often ask me they say Paul is there any way I can test a capacitor for leakage just using a standard ohm meter and the answer to that is no you need a dedicated leakage tester capacitors have many different tests and a leakage test is just one of the many tests you can see that this meter here goes to 500 mega ohms right now I have the meter across this capacitor right here so this lead runs over to here and there's a little open solder joint over here that I'm just attached to so this is between these two leads right now and it's not seeing any resistance even with this at 500 mega ohms yet if I switch this to capacitance this capacitor is rated at point zero one micro farad so if I switch this to capacitance and I just the range here two micro farad you can see that it's reading point zero one 9 so this is rated at point zero one you might look at this and say oh well you don't reads point zero one it's okay well the truth is this capacitor is horribly leaky we just haven't tested it for leakage yet so I'll remove this from the clips here and I'll just show you the rating of this capacitor you can see right there it's rated at point zero 1 microfarad at 400 volts DC so if I move this out of the way off and I'll grab a dedicated leakage tester so this is designed to test capacitors for leakage so it'll do is clip lead here again to the same area and to the capacitor now this should very quickly go down to green and then this should illuminate green indicating an OK capacitor so turn the lights off here I'll turn this on to discharge so on discharge it's not looking at the capacitor yet so right now it's just acting as it's trying to discharge the cap so what I'll do now is I'll click this on to test and as you can see the light stays red and it's right at the top of the scale so this is incredibly leaky so what I'll do now is I'll remove this capacitor and I'll take a brand new capacitor of the same value all right so I'll just turn this on to discharge and then shut the unit off I'll attach a brand new capacitor put this down here turn that on to discharge and now we'll test this so now you'll see this max out and it should very quickly drop off that capacitor is absolutely fine so I'll just click this on to discharge again and we'll do that test one more time lights kind of shining on a scale here see and see that no problems whereas the other one just stays right at the top of the scale so this is a dedicated leakage tester all the plans and the circuit board layout the schematics and the parts lists everything is available on patron for this if you want to build one of these things yourself so the replacement for this if you wanted to test these capacitors for leakage with an older tester I'll grab that tester now and set that up on the bench and we'll take a look at that this is an older style capacitor tester that uses high voltage to test capacitors for leakage if you ever plan on owning a device like this I strongly suggest that you do the research read the manual and get familiar with the device if you're uncomfortable around working with high voltages this is definitely not the machine for you this thing will source up to 600 volts across these test clips or at these jacks right here so if you click this into the leakage position wherever this little pointer is pointing that's the voltage its sourcing at the test clips so if I advance this to say 6 volts there are 6 volts across that and as you can see I can advance this all the way to 600 volts this jack is not or this little switcher is not spring-loaded so it will stay in the leakage position you need to manually click this to discharge to discharge the capacitor and remove all the voltage across these clips so if you ever purchase a tester like this be extremely careful around this so how this tester works is is this puts voltage across the capacitor and this is looking for excessive leakage current this I tube up here will display that excessive leakage current by a closed shadow angle right now the shadow angle is open and as I advance the voltage control here you'll see it briefly closed for a moment as it's charging the capacitor when the eye stays closed at the bottom here we know that we've hit the voltage where this capacitor is excessively leaky so what I'll do now is I'll click this into the leakage position and I'll advance this slowly until we hit a voltage to wear that eye stays closed so here we go six volts no problem ten okay 15s fine at twenty five and as you can see at fifty volts the shadow angle stays closed indicating that this capacitor is excessively leaky at fifty volts now this capacitor is rated for 400 volts and it's leaking at 50 so we know that it's extremely faulty since these things are attached to the line cord and then to the chassis of the scope this makes the chassis of the scope live and very very dangerous and these were hidden inside this transformer here so when I replace those capacitors I'm obviously not going to put the new ones inside the transformer they will be external to the transformer so if you recall earlier when we tested the capacitor with this meter right here we tested for resistance this was well beyond 500 mega ohms so that test didn't show us anything we tested it for capacitance with this meter as well and it read point zero one nine so if we look at the capacitor its rating is point zero one so that could trick us into thinking oh maybe the capacitor is good again there are many many different tests for capacitors and this is just another test so we have ESR we have leakage we have capacitance and the list goes on all sorts of different tests so if you want a safer alternative to testing these capacitors where you don't have to use high voltage this is definitely the device right here so this is an extremely sensitive device and it even has a forecasting feature to forecast future failures in capacitors again all the plans and everything is available on patron and you can build one of these things for yourself for very cheap much much cheaper than these thing are going for nowadays I can tell you that the transformer is now reassembled and ready to go back in the scope so I took the time to put new insulation on the wires that come out of the transformer just to make things a little bit safer and it looks a whole lot better as well I put new rubber grommets in the bottom plate of the transformer here so these are nice and soft now I replaced the cardboard box that was around the transformer so that's all replaced the transformer is held in this box and it's isolated from the actual case of the box there's a little bit of space between the bottom cap here and the actual transformer itself you can see there's a little bit of depth in there so I took a rubber grommet a large rubber grommet and cut it right in half and I put that between this bottom plate in the transformer so that holds the transformer tight in the case might be able to see the rubber grommet inside that hole there so I lined up the hole of the rubber grommet with this hole here that worked out very well now when I put the bottom cap back on this thing they originally had some little rivets that held this bottom cap on and I would say the rivets that I found and put back in are identical to what I took out and the whole trick behind that is when you buy a hole punch you usually get an eyelet kit with it they look like this and it comes with a little crimper like this and basically what you do is you just take these things and put them right through and crimp this now I had to modify this I had to cut this almost flat with this this has quite an extrusion that comes out around here so I did cut this right down close so I could get this close to the transformer as you can see that it hits the transformer right so that worked out very well this looks completely stock and that holds the bottom cap on really nice so if you ever do potting a transformer the eyelet kit that comes with a punch works extremely well and as you can see I can do a lot more transformers with this 6:32 screw will fit quite comfortably through those holes so that worked out really really nice so the transformer is ready to go back into the scope I'll get this back into this go and I'll put the brand-new capacitors in that scope as well now there's nothing inside this box except a transformer the way it should have been in the first place also have to elongate these wires just a little bit probably about this long so this will go to the terminal type where I'm gonna put those safety caps so the caps that were removed were replaced by these or will be replaced by these and these are a standard safety cap so this is an X 1 Y 2 rated cap so that replaces these ones here that have been removed now you can see that paper is coming off of this it's another interesting thing I discovered this got really loose so I slid this off and for some odd reason they just put a paper shell over something that already has writing on it so you can see here the cap says outside foil so they don't have a micro farad rating on this or a volts DC they just took the time to put that on the shell why they didn't print it right on this capacitor I have no idea so under these shells this one is still pretty stuck on this one here so underneath these shells is basically just a standard sprague capacitor so paper and foil style capacitor so those are definitely going in the garbage so these will be installed on that terminal tie strip outside the transformer where everything is very easily serviceable and the terminal tie strip is right below that large filter capacitor that we installed in the previous video so that will be done next when I have the transformer back in and we're ready to try the scope out make sure everything works I'll be back for those that are interested before I put the transformer back in we'll perform a leakage test to the same area that showed excessive leakage before so if you recall these capacitors here are tied from this point here to the blue line here you can see the grounds are tied together there so I'll test the same area so from one of the sides of the primary to the ground of this secondary high voltage winding here see if we have any leakage so I'll do the same thing I did before I'll just close the switch so I'll just join these two wires right here just like that so now I can test either one of these wires it'll go through the primary winding and we can choose any one of these leads on the secondary side we'll go right to that ground lead so technically the capacitors would have gone right across this line from each one of these right over to this ground here so I'll clip this on here doesn't matter since lead or positive to either one just like so I'll turn this on good stuff no problems let's see what happens from this winding to the case remove this here absolutely nothing from the primary side to the case and let's test from the secondary side to the case no problems everything is looking great and this one isolated winding to the case absolutely nothing so the transformer is looking good the power transformer is installed in the unit and I've also added a fuse holder and a fuse so you can see I've installed these two capacitors that we're inside the transformer here on this terminal tie strip and I'm using these types to tie the line cord into the transformer now whenever you're installing one of these safety capacitors if there's going to be a side that's going to be closer to the chassis obviously this would be the side that you would want to tight as you can see that this side runs over to this side of the capacitor so it's just a little bit of added protection so to say that this was close to a grounded surface like a chassis you can see that this if it's tied to the actual chassis would be a more sensible idea than of course having this side here tied to the chassis and then this tied to the line because you could get very close to the chassis with the line cord just something to keep in mind when you're using these safety capacitors that was taken into consideration when these were installed here so this is just about ready to go back in the case all of these wires are what links the bottom portion of this scope into the upper portion of the scope once I have it all back together we'll do a leakage test between the line cord in the case of this and then it will fire it up and see if we get a trace on the screen the scope is all back together let's perform a leakage test from the line cord to the chassis so this here is ground if you can see that there in the camera this little post here is ground it a little bit darker so that we can see the display on this just a little bit better so what I'll do is I'll take positive lead of the tester and just clip it to the ground it really doesn't matter which order this is in and I'll just select one side of the line cord here click this on just like that that out of the way and this on and let's test for leakage looks good now the moment of truth let's see if the scope lives so what I'm going to do is plug this into my isolation transformer and Variax supply and I'll turn this on just get the light off the CRT here see that a little bit better let this warm up for a moment oh I see a trace there it is looks great project successful thanks for stopping by the lab today I hope you enjoyed this video involving the departing of this transformer if you did enjoy the video you can let me know by giving me a big thumbs up and hang around there'll be many more videos coming like this in the near future we'll be taking a look at a lot of very interesting antique and modern electronic devices together if you're interested in taking your electronics knowledge to the next level and learning electronics in a very different and effective way you might want to check out my patreon page I'll have that link just below the description and I'll also pin that link at the top of the comments section as well so you can click on that it'll take you right there if you do go check out the community section there are a lot of people sharing their ideas and projects there as well alright until next time take care bye for now you

Channel: Mr Carlson's Lab

Views: 148,227

Rating: 4.9553986 out of 5

Keywords: fix a transformer, depotting a transformer, learn about transformers, capacitor leakage tester, transformer tar, tube equipment, test equipment repair, custom tools, tube amplifiers

Id: spwyGQuIXwc

Length: 47min 13sec (2833 seconds)

Published: Tue Jun 26 2018