Are Your Capacitors Installed Backwards? Build this and find out

hi there if you're into restoring old receivers or older or even building amplifiers problem we find this information rather interesting so those orange dip brown dip green dip and those little yellow axial lead capacitors and many more capacitors have a polarity in circuit and should be installed in the circuit the correct way in order for them not to pick up hum from adjacent parts of your amplifier or radio or to pick up interference from adjacent parts of the chassis whatever they're installed into so in this video what we're going to do is we're going to discuss why these capacitors have a polarity and then we're going to build a little circuit that will help us locate this polarity quickly we all know that if you're restoring a radio or an old guitar amplifier they usually have a handful of capacitors in them and you really don't want to be doing this while you're restoring the receiver or amplifier so we're going to build a little circuit that will help you grade them with an oscilloscope very quickly and then you with a little felt marker you can mark the band end or as it was called in the old days the outside foil end of the capacitor so let's get into the video and start discussing why these capacitors actually have a polarity here we have two very common circuits that you'll find in a lot of vacuum tube gear this upper circuit here you'll notice is in a lot of guitar amplifiers or high fidelity amplifiers or stereo receivers this really is just an audio amplification chain here this bottom portion of the schematic I've kind of drawn to represent either an if' amplifier or an audio amplifier of course we'd have to amend this transformer to represent either/or but we're not going to get too crazy about that right now because it's all about just learning which way we need to install our new capacitors in this circuit for the best circuit performance and the least amount of interference so way back in the day they used to make capacitors that looked like this and if you ever find a capacitor like this in any kind of gear that you're working on it has to go these are all faulty by now and they leak now when I talk about leaking I don't mean that they leak physically they're not leaking a substance like oil or goop out of them they leak DC across them so whenever you hear the term leaky capacitor that means that they're leaking direct current through them capacitors are supposed to block DC and pass alternating current through them so when they leak that means that this capacitor effectively turning into a resistor and that is no good for the next stage so what happens in these capacitors is they've got paper inside of them that's gone acidic and it's basically dis turning into a big resistor rate now and when these capacitors turn into resistors they bias up the next stage and cause the tube over here to draw heavy current it causes damage to the circuit you burn out plate resistors and AF transformers and it does all sorts of bad things so you want to get rid of these capacitors and replace them with a modern equivalent like a an orange dip or a brown dip and I'll grab one of those here in just a minute to show you so back in the day when these were brand new they're great capacitors they didn't leak or anything and they were nice enough to mark the outside foil end of the capacitor by putting a band on it and printing outside foil on it now the outside foil and means that this lead on the capacitor comes into here and it also attaches to an outside foil jacket that's just great underneath this paper here and it shields the entire capacitor so if we were to tie this to the chassis this whole capacitor would be shielded right up to this point right to where this lead goes in this lead goes it to the inside layers so in effect these capacitors actually do have a polarity now so do a lot of the modern capacitors and if they're built correctly they'll actually be made with you know metallized polypropylene or you know PVC or whatever they're building their new capacitors with and of course whichever new style capacitor that you end up buying they will have an outside foil jacket connected to one end it's just that they didn't spend the time to actually mark it and that's what we're going to do in this video is we're going to locate that odor odor foil or the outer metallized polypropylene layer so that when you install your capacitors into circuit you're going to pick up less hum and a less adjacent interference and you know either you're not going to get oscillation because you have a really large exposed surface hooked to a high impedance portion of your circuit so now these capacitors we'll just use this as an example for a modern capacitor so say this was a brand-new modern capacitor okay if we were to install this into the circuit this end here would go to the lower impedance point always so this end here with the end with the band if we were to use this as an RF bypassing capacitor would always go to the chassis and this would go to the the grid of the tubes say the screen grid if we wanted to keep RF off the screen grid or something like that it would go like this because when we tie this end of the chassis this entire capacitor is shielded right up to this point now if we hook this up in Reverse and say we tied this end of the chassis and this end of the tube socket we'd have all of this area that is completely exposed right up to this point so of course we don't want to have that because that's more exposed area and of course we're going to pick up more interference that way especially if we have a filament or a heater line running past this that's that's definitely no good we definitely want this end to the chassis side now when we're hooking this up to a standard audio amplification circuit here this capacitor would go in this way because the band end or the outside foil and always goes to the lower impedance portion of the circuit and the lower impedance portion of the circuit most of the time is the plate of the preceding stage here or the earlier stage I should say so this band end will always go towards the plate and this end always goes towards the grid in this particular circuit and in this capacitor would be the same way and if we had a capacitor on the input here it would be the exact same way again on this bottom circuit here we'll notice that there is a capacitor missing on the screen grid and this would be considered an RF bypass capacitor we want to keep RF off the screen grid here because we don't want this screen grid to amplify any kind of oscillations or any kind of interference that's in the chassis so by mounting this capacitor in we would have to mount the band end to the ground or the chassis and that would tie to the screen grid now of course we don't want a lot of lead inductance there so we want to keep the lead as short as possible but again you have to use some common sense you don't want an extremely short lead so that when you're soldering it if you have a newer capacitor you're going to melt the poly the metallized polypropylene with the heat of your soldering iron you'll probably need to leave a little bit of lead so that it'll dissipate some heat so again these capacitors need to go in like this and they need to go in like this and they need to go in like this okay so depending on what stage or what what kind of schematic you've got going on so now we have new capacitors that look like this right here you can see this this has no markings on it and when these capacitors are created they're going down the assembly line this way and then they get the the writing or the printing on them this way or they'll get them on this way because it really doesn't matter they're in a machine that doesn't really pick which way they go down the line so they could be any old way and we need to find out which end which lead is attached to the outermost metallized polypropylene or we could call it the the actual shielding inside the capacitor which would be the outer the outer layer them outermost layer of this capacitor and that's very important so that we install this into the circuit the correct way because we don't know now a lot of people think that when they buy these orange dip capacitors that oh look they've been really nice and they've marked that well really have they this is how you test for the outside shielded end of your capacitor or the outside foil and or outside metallized polypropylene layer however you want to call it we're really just looking for the shielded end of your capacitor and this is how you find it using an oscilloscope and a very simple little setup like this which is basically just a BNC cable with the center conductor attached to an alligator clip and the shield is also attached to an alligator clip I have them right now just clip together to keep the noise off the screen so if you have a newer modern DSO that goes down to about 5 millivolts per division you should be absolutely fine right now this is running at 2 millivolts per division and you know we're not going to get too accurate with the readings because really I'm just acting as a random hum antenna in order to determine the outside foil end of these capacitors and I'll explain that here quite shortly so the first capacitor we're going to look at is this old wax capacitor now we wouldn't want to use this in circuit because this capacitor is well past its due date but we're really just looking at a shielding aspect of this capacitor so this will be just fine for this test so what I'm going to do is I'll hook this into circuit the correct way and we'll look at the signal on the screen and the amplitude here and then we'll reverse this capacitor and see the differences so right now I'm disconnecting this thing up and this is the way that it should normally be I'm acting as the hum antenna right now I'm holding the the case of the capacitor right now so you could look at me as a very nearby heater line running past this capacitor and in a chassis or something like that so that's the amplitude that we got with it hooked up the correct way you can see the banded end is connected to the outside shield of the cable this is the lower impedance portion of the circuit this would be the chassis and we're always looking for the lowest amplitude when we have found the lowest amplitude we have the capacitor hooked up the correct way when the amplitudes high it's hooked up backwards so what I'll do is I'll hook this one up the other way and we can tell that we have this hooked up backwards because now the outside foil which is the the shielding on this capacitor is capacitively coupled to me and I'm feeding signal into my oscilloscope so that we can see here very simply that this capacitor is now hooked up backwards remember we're always looking for the lowest amplitude and then we know when the negative or the common lead of our oscilloscope is hooked to that and when we have the lowest amplitude that is the end that we will mark as the outside shielded end or the outside foil under whatever you want to call it so that's this capacitor here so let's grab a newer orange dip capacitor and take a look at it so here's a newer orange dip capacitor and we have a line here and we might think that oh that line indicates the outside foil and well let's test that out I'll just hook the capacitor up to it right now it's much easier to hook this up off of screen here so there we go so now I've got this outside shield of my braid hooked up to this and this would be considered the chassis and this here would be considered the part that goes into the higher impedance portion of the circuit okay so now what I'll do is flip these leads around now if I flip these leads around and the amplitude goes down that means that this side is not the outside foil and remember the side that the shielding is on is always when the amplitude is lower is the outside foil and so what I'll do is I'll reverse these leads right now and look at that we have lower amplitude here so this line here does not denote the outside foil and this side here is the shielded end of this capacitor so again I'll hook this back into circuit the other way and we can see that we have more amplitude this way and then if I change these around and see that there's almost nothing there so this side here would be the side that we would want to connect to the chassis we would mark this side here with a line as the outside foil okay so let's grab another orange dip capacitor right here and test it out the same way so I'll hook this up the way that we would think that it's hooked up this is the band end here so we'd figure that that is the outside foil alright so now what I'll do is I'll reverse the leads and we can clearly see with this capacitor that this side here is definitely not the outside foil or the outside metallized polypropylene or whatever metallized PVC this here this side is so this here would be considered the shielded end of the capacitor this is the side that would attach to the chassis again I'll reverse this and you can very clearly see that this is not the shielded end so let's test an older capacitor here I have an older kind of a burgundy dip I don't know what you would call this but let's consider the line end on this one as the outside foil so I'll just hook this one up now okay so here we go alright you see the line is on this end and we have the common or the negative lead hooked up here alright now I'll reverse the leads and we can see on this capacitor that line does denote the outside shielded end of the capacitor so on this capacitor you could regard this line as correct now whether these capacitors are going down the run like this and they're going down the run like this we don't really know because I don't have more of these to test but it just so happens on this capacitor that this and here is the shielded end okay so let's take a look at this old general Instruments capacitor alright and let's test it out and see if this band end is the outside foil so I'll hook this one up the way we would think it would be hooked up properly again we have the band end hooked to the ground or the common this would be considered the chassis okay now I'll reverse it and we can clearly see that this is not the outside foil and on this capacitor either so really the bands on the ends really can be considered either way with a lot of these capacitors so really you need to test them in order to really know what side is the outside foil and you can verily very clearly see that there is a polarity to these capacitors so I'll grab one of my my Brown dip ones here all right and I'll hold this one this one has absolutely no markings on it so we'll test this one out here and see this one here okay and I'll reverse the leads it's just shorting here got these leads I'll twist it up there we go so we can clearly see that this end here is the band end right here even though there are no markings on this capacitor so you can see the difference is there there's the lower amplitude this way and I'll reverse the leads and we can see that we have higher amplitude this way so this end here is the shielded end so now what we want to do is since we're going to be testing these things you know we're going to you know if you're replacing a whole lot of these things in a radio you're going to be you know basically have a small bag full of these things so you don't want to be doing this as you're you know putting these things in the radio you kind of want to pre grade these things and find out which end really is the Bandon so that you do install these things correctly to short these leads out here so so what we're going to do is create a small circuit that does this a little bit easier for us and we'll check out maybe a couple of different ideas and see what we can design here and make a little make a little test jig for these things before I start building a small project I usually like to check my own stock and see if I have enough parts and pieces to make this with the with the parts that I have on hand so I would like to build this into a smaller project box and it just so happens that I have another one around I built the TDR out of the same one I can't find the other project box I put it in a very safe place so that I would find it the next time as I can as I can now see so anyways I'll locate this other project box it looks just like this one here except of course there's nothing in it it's just a solid you know cast box here so I'll end up using this box here and the reason I want to use this box over a plastic box is this is completely shielded you got to remember we have an oscilloscope that's down at about 5 millivolts per division and maybe even 1 millivolt per division so if we have a plastic box a lot of noise is going to get into there from anything that's basically around it the thing is any kind of wire length inside this box if it was plastic would act as an antenna and we'd be picking up all sorts of just noise and random garbage so we want to do is we want to have everything enclosed in a solid a cast box here another thing that we have to think about is you know a battery so I'm going to need to install a battery in here now most likely going to end up using a 9-volt battery for this so you know it's going to take up a small portion of this box so I have to locate things inside of this project box so that you know this whole thing will work out you know I need to put a BNC jack on here you know all I need to put a switch on it somewhere the battery will have to be mounted in here they'll have to be a small circuit board in here that you know all of our parts and pieces are going to be on and we also have to think if we're going to say I'm going to have two alligator clips sticking out of the top of this box or something like that alright now I'm going to also have to have an LED beside each alligator clip so that I know when this thing is moving around like this one it's reversing the polarity of the capacitor so that we can note that you know the amplitude difference on the screen we're going to have to have something that's going to mark the side that's the band end so I'm going to have to have maybe some rubber grommets and then you know maybe some LEDs on the top of the box so everything has to be taken into account because we can't you know push the battery down on top of the LEDs and we also need space for the for the wires to come out of the top of the box so the battery will have to sit over to one side and this is all stuff that you have to think about before you plan this so what you do is of course you get your box and you know you put the battery inside and you move things around and you know you pawned over some things for a little while and then when you you know come to thinking okay you know this layout is going to work then of course you can start building with that layout so now in order for this to make testing easier we obviously need some form of a circuit that's going to take this you know capacitor and it's going to reverse it and of course we don't want any imposed noise from the circuit that it's around so in order to make a circuit that's going to reverse this we're going to need something that's going to look like this so we can look at this as right here if we were to have the capacitor under test right here this is the capacitor under test okay and say this here is the the scope common and this is the scope you know that the center conductor will just put plus here for just for ease of drawing okay so this is the center conductor of the oscilloscope probe and this here is the scope probe common so if we want to have this in the circuit say this is the negative side of the capacitor here we're going to need to close this switch and we're going to need to close this switch in order for the positive probe of our oscilloscope or the center conductor of the cable to be attached to this side of the capacitor which then would make this this side here and then of course this would run to ground so you can see we have a circuit here now so then in order to reverse this capacitor in order to flip it these two switches would have to open and then this switch and this switch would have to close and then of course that would make this side running up to the to the center conductor here and then this side here would end up becoming the common side because this switch is connected to ground and we're going to also need some form of say an LED or something at this point to denote when this side here is the the common side or whether this side here is going to be the common side so we're going to also need two LEDs to do that so now we can do this with relays and of course we're going to have a little bit of current consumption if we do that we're going to here click click click click inside this box or we can do this within IC and I'll probably end up using an IC because there's a you know limited current draw with n IC we you know there's a bunch of ICS that that basically work as a single pole single throw switches and you know I'll find something that's rather common to use and we'll make this particular circuit using a bunch of ICS now if we use an IC and it's got a bunch of fats inside it we're going to also want to have something on you know this particular point here which basically is you know to do like this one diode like this and one diode like this and that's going to also limit this basically to about point six or 0.7 of a volt on each side so just say there's a bit of a charge on that capacitor so you forgot to discharge it a little bit or if there's you know you have static you're not going to zap this I see if we use an IC so this is basically just going to protect it and limit the voltage that goes into the circuit now of course you would always make sure every single capacitor is discharged before you stick it into circuit and all this is going to do is protect the eye see that these switches are in and of course we would want the same thing on this particular side here and it would be exactly like this so basically all that's doing is this is limiting this input circuit were cap acid or under test is to about point seven of a volt now keep in mind that we're testing most of this down at around oh no 10 you know maybe you know with our amplitude maybe we're exceeding 50 60 70 millivolts with the humming are and that we're imposing into this capacitor who knows but this is going to be up around six or seven hundred millivolts just about a volt so you know this is a well beyond our our our test so this is just protecting this here so now we're going to also need to do is we're going to need to implement some sort of a circuit that's going to close these two and close these two and then it's going to have to do this right in order to flip this capacitor back and forth and back and forth so we're going to need some sort of a flip-flop probably a D type flip-flop or something like that and then if this is an in and I see these are going to be controlled so this side here right and this side here would go to one leg of the flip-flop and then this side here and of course this side here would go to another part of the foot flip-flop now keep in mind that this is just only a rough sketch and I'm just trying to get the idea across when it comes to actually designing this we'll go over to the whiteboard and take a look at it there so now that we have a flip-flop that's basically just going back and forth like this you know once this one this side is positive say you know we're going to probably not use a just a 74 Hz we will probably use a CD 74 HCI C's for this because we are dealing with a 9-volt battery just 74 Hz logic is usually only good to between both 5 & 7 volts maximum so we're going to be using a 9-volt battery so we're going to be wanting to use parts that start with CD and of course we'll take a look at the data sheet just to make sure that you know it will be fine around the 9-volt area so now that we have this this this type flip-flop here now we need also a timer that's going to set out a pulse into this that's going to tell this to go back and forth like this so of course when this side is high this side is low right and then when this side is high this side is low so basically what this is going to do is it's just going to close these two switches and then close these two switches and then close these two so you know when these two are closed these are open obviously and it's just going to go back and forth like this and we also want to set the timing rate of this timer so that when we have this thing on the bench and we're looking at say our oscilloscope here we want it to go slow enough so that when we can see the amplitude change on our oscilloscope the amplitude goes down and then the amplitude goes up we want to have a chance when it goes down again to look at the box and note which led on which side of the box is going to be led up so when we know that you know the amplitude is low and this led is lit up we'll know that this side here would be the band end of the capacitor so that's what we want to try and do so these are the parameters that we're basically dealing with we have a 9-volt battery so we know that we're going to need like you know is s CD 74 HC parts or just CD parts the 555 timer is good for nine volts so we don't really have to worry about that we'll use a five five five over here probably a D flip-flop or something like that and I'll have to figure out some really common part for this so that way you know it's easy to put together now if you have a bigger box you don't need to use a small box like I'm doing you can build this onto that dumb you know that proto board stuff and you can use through-hole icees I'll probably end up building this for myself with surface mount stuff just so that I can fit it right inside this box and then you know this box will have a B and C come off of it and a power switch and it'll probably have two little alligator clips now the the cables that are going to come out of this box I want to be shielded right up to the alligator clips because you know if we have just two long wires sticking out of here those are really to acting as two antennas so the more shielding we can get right up to the alligator clips the better so I'll have two small shielded pieces of coax coming up here and of course we want you know a little bit of lead length so we can move them around if we have you know large axial capacitor we can clip them onto the ends or if we have one of the newer style ones we have this one here we have one of the newer style ones like this you know we can just you know put the two leads together and clip them in like this so the whole idea is to make this thing functional especially if you're going through all sorts of different types of capacitors you know we want this thing to be about just as versatile as we can make it so now that we have the plan here I'll figure out an actual circuit and I'll draw it up and we'll head on over to the white board and I'll explain it there this is the circuit I've designed for our little capacitor testing so I ended up using a CD 74 HC four zero six six to flip the capacitor around in circuit now this is an IC and it's a CD 74 HC four zero six six it's not just a 74 HC four oh six six and the reason that I use this one is that it will go up to ten volts remember that we need to keep the supply voltage of our ICS well within a safe zone I'm using a nine volt battery over here to power this and again this is all just due to size constraints I have that little aluminum box or that little cast box that I showed you that I'm going to end up fitting this all in if it's around here somewhere I still haven't found it but I'll fit all that into that box again you know you can build this into any kind of size box if you have a larger aluminum box you can you know of course use a different kind of battery style power source for this at you know a bunch of double-a batteries or whatever fits in that box just keep in mind that the box has to be either solid metal or solid aluminum or a cast box some sort of conductive box because again our Cilla scope is running down you know between 1 and 5 millivolts it's going to pick up any kind of noise no power supplies running into this thing at all it should be battery-powered so we'll get back to the circuit I've drawn this I see the same way that you would kinda look at Relays just yet make it a little bit easier to understand so how this IC works is really quite simple it really is just four switches inside of one IC so pin 13 pin 5 pin 12 and pin 6 are the control pins so say pin 13 goes high that'll connect pin 2 and pin 1 so technically it just closes the switch inside so pin 13 and pin 6 are tied together pin 12 and pin 3 are tied together so basically it's just closing the switches like this and this is all done within an IC there's very low current consumption you don't get the clicking from a relay and you know it's a it's a real consistent test because we're using FETs inside this in order to switch this in circuit now there will be a little bit of resistance in the switch and I'll explain that a little bit it's between 15 and 20 ohms but that's absolutely fine for testing these capacitors there'll be no issues with this whatsoever so this was a really good solution the cd70 for AC 4 0 6 6 is a really common part it's an off-the-shelf part you should be able to find out with no problems again you can build this through-hole you don't need to build a surface mount the only reason I'm building this surface no it's because in my little box it's is hiding here somewhere and I'll put all the stuff inside that little box so ah these are b'av 99s these are just their two diodes in 1 SOT 23 package you don't need to use the Vav 99 you can use a 1 and 4 1 5 2 or a 1 and 9 1 4 or if you think you're going to be crazy and leave a capacitor charge and stuff it into the circuit you can use a 1 in 4 double O 7 s or whatever you want to use remember this is just working at a really low frequency is you know you're coupling the 60 cycle signaling from your body really and you know just you know inducing hum into the circuit so that you can see which end is the shielded end so really not too picky so I use the Vav 99s just because they fit on a little circuit board quite nicely so and all I'll get into this here in a little bit I've already got that little circuit board already pre drawn and ready to go and we'll get into that next I'll show you how I've drawn that up so that's one of the reasons that I use these they just they fit on there really quite nicely so now here I've got a CD 401 3 which is a flip-flop is a D style flip-flop and what that what this really does is when it receives a pulse in pin 11 of this I see what it does is it just basically this pin will go high this will go low and then it will receive another pulse and it turns the other way and it just keeps going back and forth like this now you can see I've got two really high brightness LEDs here and the reason that they're high brightness is because I'm using a 22 K to ground resistor and you can use one or two it really doesn't matter the reason they're I'm using this is because they pull very very low current and they are still pretty bright at that point so I don't want to use up my battery power lighting LEDs you got to remember in the circuit one LED will always be on it's just going back and forth so when this side here goes high this LED will glow now this LED here should be positioned by the negative part of the switch so pin eight and pin nine it were pin pin four and pin eight run out to your alligator clip that's where this LED should be located alright so where this LED should be located should be close to pin 1 and pin 11 so what's going to happen is is when this side goes high it closes this switch and that what that's doing is that's bringing this side of the capacitor to ground and we remember that we're looking for the negative side of the capacitor or the shielded side of the capacitor and you want this LED close to this side you want the red LED close to this side so when this side goes high this one here is pulling this side of the capacitor to ground again we're looking for the shielded side of the capacitor if you have the LEDs reversed you'll end up marking the wrong side of your capacitor and I'll show you how to test for that in the end to make sure that you have the LED on the right end just in case that's a little bit confusing again the we have a pulse going into pin 11 here so again this is just going like this and you can see the action with the LEDs the LED you'll see the LEDs move back and forth this is a five five five timer and what this little 555 timer is doing is just creating the pulses in order to tell this flip-flop to do its flip-flopping so it's just going to keep it doing this now I chose a 180 K resistor in a 1k resistor because I find that to be a very nice balance you don't want this to go too because you're not going to be able to look at the screen and then all you know really quickly look down to the box and then see which LEDs letting mark the line on it right you want enough time so that you know when you see the the amplitude goes small you can look at the box see which LEDs lit and draw a line on and then by that time it's already back over to the other side again and I'll explain all this in the end and you'll see how this actually functions so you can speed this up if you want if you find that this is a little bit too slow and you know you want to be Superman as you're you know grading all your capacitors in your uterus hammering them through really quick you can change this 180 K resistor down to 150 K and it's going to go quicker 120 K and you're really working alright if you find that 180 K is too fast up into 220 and you'll have plenty of time to sit there and have a sleep between the LEDs as they're switching back and forth okay so this hundred an eighty K resistor you can put a VR in there again I'm keeping it simple I'm I'm dealing with size constraint because of that little box that I've got so I just want this thing basically turn on a switch and the thing just starts doing its action and I can great cap so it's just a happy medium so 180 K and 1 K work very well I'm using a 22 mic tantalum capacitor down here and the reason I'm using a 22 mic tantalum capacitor is because I have a lot of them so that's really the only reason there's a point 0 1 cap coming off of 5 just to keep noise out of the 5 5 5 you'll see here that these are all the supply lines for all the ICS we have pin 14 and pin 14 pin 7 and pin 7 for both of these ICS and for 8 and 1 for the 5 5 5 so 14 14 4 and 8 are all positive so 4 & 8 and this is pin 14 and there's a pin 14 on this that also has to be tied to positive and we have pin 7 pin 7 and pin 1 so there's a pin 7 on this IC that has to go to ground there is a pin 7 on this IC as we can see here that goes to ground and then we have pin 1 here going to ground and that's really just the supply again you can put the switch in the positive or the negative side absolutely fine whatever you think will work just fine for you so I've got a 22 mic cap on the supply here just to keep noise out of the circuit when this thing is switching what else can I tell you here I think that's pretty much it this will draw between to eight milliamps somewhere in there depending on the ICS and the manufacturer and everything that's really quite nice if you use release you're going to end up with quite a bit more current consumption so that was the whole idea of of using a 9-volt battery and a bunch of ICS we can you know we'll get a really long life out of this out of this little switch so everything should work just fine scope common goes to pin 10 and pin 9 so basically pin 9 and pin 10 of the 406 6 we'll just tie to the chassis or to the box and then the BNC Center that you have coming rate that goes right out into your oscilloscope will tie rate to pin 2 and pin 3 so and of course that's that's you know a continual and then you know this isn't moving this is your scope pot yours in your scope comm there's nothing moving there that's that stays there and then of course the switching is going to do its switching at that point inside the IC and flip that capacitor around as this 555 timer is telling this flip-flop to go back and forth and that's pretty much it so what I'll do is I'll take you over to the computer now and I'll show you the little layout that I've got designed up and it's a service mount layout again you don't have to do it surface mount you can build it through-hole or however you want to build this you can build a dead bug style whatever works for you so let's head on over to the computer this is the surface mount version circuit board that I've come up with for this little capacitor tester so this is really quite blown up this is a really small circuit board but I've just enhanced it so that it's easier to see on camera here so this is the top layer the green layer is the top and the black is the backside of the circuit board so this is a double-sided circuit board this little I see here is the 555 timer this is pin 1 this is the timing cap that 22 micro farad tantalum here these are Oh 402 parts this is 180 K resistor this is the 1k resistor and this is the point 0 1 micro farad capacitor off pin 5 this here is the other 22 micro farad tantalum that's across the supply this here is the cd40 1 3 which is the the flip-flop and this is the 4 0 6 6 over here the is CD 74 HC 406 6 this is what's going to be doing switching here these here are the screws where it mounts to the chassis of that little aluminum or a cast box that I've got these are the resistors that's on the back side this resistor is a 22 K resistor and this is the LED this LED correlates to this side this is the test lead that runs out this side this is the center conductor and I will solder the shield or the braid of that little piece of coax to this piece of the circuit board here and then of course we want the LED close to that rubber grommet where the where the test lead runs out and it's the same for this side this is where the center conductor of our test lead runs up to the alligator clip the shield of the coax will solder to here and this LED correlates with this side so these are the high brightness LEDs here these are 1206 parts here these are 22 22 K resistors this is where the supply or nine volt supply runs in right here and this is where the BNC signal runs out this goes to the BNC jack on the box and that goes out to our Scylla scope from this little point here and that's really how this works so this is really quite small and I'll show you exactly how this is going to go together here in the next shot here is the completed little capacitor testing box here we can see that I've got my alligator clips fastened to some shielded Koh access to some teflon coax here the shielding runs up to about this point here and about this point here you don't need to use teflon coax you can use any kind of coax you want I just have a bunch of this stuff around I've put some heat shrink on the ends here just to stiffen things up where that the center conductor runs out to the alligator clip because you know we're going to be moving this around and moving in in and out of circuit quite a bit and I want to get some longevity out of this without having the connections break now of course nothing sticks to teflon very well so I've left a little bit of braid exposed and this heat shrink here it has a little bit of glue inside of it so it sticks to the braid quite nicely and we see the corresponding LED for this wire here and the corresponding LED for this wire here when this LED is lit this one here is tied to ground and when this LED is let this side here is tied to ground so we know which end to mark our band on these are two little rubber grommets here that I put in this is the BNC Jack here that will run out to the oscilloscope and there's a bunch of screws here that just hold the circuit board in and this is the on and off switch on the side so on the bottom half you can see here I've got a little 9-volt battery stuck in there and there's a little piece of butyl tape that's just holding it in this is the circuit board that I built and this is the little switch in the negative lead I'll just zoom in to this here so we can take a little closer look at the surface mount stuff so you can see the ICS here that's the little 555 timer that's the 406 six down in there and that's the 401 3 flip-flop and that's the little tantalum capacitor the timing cap and so on and so forth just like on the layout those are all the little Oh 402 parts right down there the hundred and eighty K the 1k and the the point zero one mic capacitor you can see how I've soldered the braid of the coax right to the circuit board here and then the center conductor runs up to this little spot this little SOT 23 package part here is that b'av 99 diode that's just protection so I don't zap the IC in there that's the same on this and I soldered them in sideways because if I ever need to replace them their be pretty easy to get out this way and put back in again you can use a 1 in 400 seven or a nine one four or anything like that you know it's again we're you know we're dealing with 60 cycle frequency here so there's nothing that needs to be too incredibly fast see what else can I tell you those are the LEDs that are soldered in you'll see that there's a space between the circuit board here in the actual case and that's because there's parts on the backside of the circuit board and there's also a soldering on there so when I put the the bottom portion of the box together here I had to cut this out on the corner here and on this corner because the circuit board goes you know very close to the corner here and they've got this kind of extruded lip that runs all the way around the entire box here so there's enough space between the backside of the circuit board and the case to leave this strip in here it just goes between the circuit board and the case you can see here here's the circuit board that will go right in between here and that's pretty much the box so when we turn the thing on this is about the speed that it runs out with the with the 180k resistor here you can see how fast that moves back and forth so that gives us enough time to mark our capacitor and you know of course look at the screen in the you know load a new capacitor I think that's about a nice comfortable speed for grading these capacitors so next let's hook this thing up to an oscilloscope and see how it works we're ready to check the polarity of some capacitors in our test jig so I've got the oscilloscope set to 5 millivolts per division I've got the alligator clip shorted here and I'll plug this in and I'll show you that it's a relatively quiet circuit and see how quiet that is right now now you got to keep in mind that through this I see when this side is grounded it's about 17 ohms to ground and then when this side is on at 17 ohms to ground so we have 217 or around that own paths 1 from positive and 1 to ground and that's just the basically the resistance imposed by the IC itself so even though we still have this you know we're going to still pick up noise from the oscilloscope if we bring it close to it in everything but you know for this actual test this is absolutely fine and for this little test jiggets is fine so when we open these alligator clips you're going to see lots of noise on the screen and that's absolutely normal because these are acting as antennas and this is actually just picking up noise from the scope itself even you can see the amount of noise that comes in from the CRT so when we put the capacitor in here under test it actually acts as a filter across the circuit itself so there is no problem with the amount of noise that we see so what we'll do now is we'll put a capacitor in here let's take this orange dip capacitor and test it out and Mark the band end so here we have me being the 60 cycle antenna again and you can see the difference in amplitude here as its switching so we see this LED is on and the amplitude is lower so this is the band end you see so now that we see this LED on we would mark this end as the band remember we're always looking for the lowest amplitude so I'll take my Philip marker and I'll put a little line on this end and I'll know that that now would be the lower impedance portion of the circuit this would go to the chassis or this side would go to the plate side if we have this in an amplifier again we can see that this side has a band on it but we can see that it doesn't really mean anything you know according to the outside shielding or anything this might be some sort of coating that they've put on or I don't know what they're doing and why they've put this on this one end but this side here you know clearly denotes the outside foil or the outside metallized polypropylene or metallized PVC layer okay so there's one so we've marked this one and you can see the speed is comfortable so that you know what's you know you're not losing control of what you're doing so put this one in all right and I'll put my fingers on here all right so we know that this end is the band end also okay so I'll mark this as the band end now if you don't want to leave your felt marker on there you know you can use an ink that will easily come off I find that you know a little bit alcohol will just remove these lines even if it is one of these sharpies so you know a lot of people don't want that line on the capacitor when it's in circuit I've kind of learned to live with it I kind of like to have the the capacitors clean myself but that's fine for underneath the chassis I'm now just beginning to leave the lines on like you will end up seeing in most of my videos so this one here this side here the this opposite side here this one on this side is the band end where I've drawn that little black line so let's test another one so we can see that the opposite end on this capacitor is the band end so this end is the band end on this capacitor so you can see there really is no rhyme or reason for these capacitors you know they're just kind of going down the line any old way they're the same capacitor and they're just printing the the the labeling on any side there so it really is important to mark that off let's test out this one here and check out its band and okay is that in the shot there it is okay I'll put my fingers on here okay so this end is the band end right here so now we would mark this end as the band end and that's just how simple it is to grade and check your capacitor so you know that you're putting them in circuit the correct way and that's how this little fixture works so what we're going to end up doing next is I'll show you how to measure which end is actually supposed to be the the negative end so that you have your LEDs corresponding to the correctly just in case you did find that a little bit confusing alright this is how we tell how we've got the right LED on the right lead so this is the lead here that we're going to test and we want to know if this LED is corresponding to this connecting to ground so we've got our our meter on ohms and we have our lead going into the alligator clip here and you can see that at 17 ohms when this LED comes on see that so we know that this end is connecting to ground and we have our polarity right so what I'll do now is I'll move this over to this side and you'll see roughly the same measurement on this side isn't LED there and lamp all right let's me trying to get a good ground on the box here there we go so that's how you tell so if you wire your LEDs up and you have them backwards if you leave some lead length you can just swap them around if you don't build a circuit board or something like that and that's how you tell that you've got the LED connected to the right side well we've come to the end of another video I hope you find this little circuit useful and I hope you enjoyed the video if you did give it a big thumbs up and hang around I'll try to make more videos just like this in the very near future take care bye for now you

Channel: Mr Carlson's Lab

Views: 609,333

Rating: 4.9135652 out of 5

Keywords: creativedesigncomponents.com, creative design components, capacitor polarity, orange drop, mylar, esr, capacitor testing, capacitor rating, brown drop, green drop, yellow jacket, outside foil, capacitor shield, sprague capacitor, wax capacitor, leaky capacitor, Capacitor (Invention), amplifier capacitors, radio capacitors

Id: BnR_DLd1PDI

Length: 49min 35sec (2975 seconds)

Published: Mon May 18 2015

Reddit Comments

[u/ytsoc]

TL DW, non polarised, film caps have a shielding that is connected to one of the leads.

This lead was marked in the past but on present caps is no longer marked(even if they have a marking it's not a indication for the lead we're interested in )

This is important in circuits that deal with small signals(audio and what not) because if the cap is mounted the wrong way , it can act as an antenna .

I've had this happen to me in an amplifier, where if i touched a film cap on the signal path, i would get a hum, but i did not know that caps had internal shielding so i didn't investigate further

[u/TurnbullFL]

How important is this? Never heard of it ever being a problem before.

[u/1Davide]

For those who do not want to watch a 1 hour long movie, here is the TL;DR:

In sensitive analog circuits, the side of a film capacitor that is internally connected to the outer foil (may be marked with a line) should go to the least sensitive of the two nodes.

[u/EkriirkE]

Is this just alternating a DC-biased sine wave? If so, why not just have a normal AC sine wave and see which half of the wave is more suppressed?