Which Capacitor Do I Use? Tech Tips Tuesday

hi there and welcome to another tech tips Tuesday in this episode we're going to check out choosing the correct capacitor for its intended application so whether you have an RF circuit an if' circuit an audio circuit or whatever choosing the correct capacitor is crucial for that circuits performance temperature stability and a whole bunch of other factors that's what we're going to take a look at in this video so let's get started here are the capacitors that I'm going to be talking about at the white board not in any specific order so these first two capacitors here are paper and foil capacitors and they are both faulty by now so if you have any equipment with these capacitors in them they've got to go now you may have tested these with your capacitance tester and said to yourself well they they test okay you know this one reads 104 so that's point 1 micro farad and this one is point zero 5 and it reads absolutely fine well that's not a leakage test leakage test is a completely different thing now when people say that these capacitors go leaky that doesn't mean that they're leaking a substance like liquid or anything like that it just means that they're leaking DC across them so if you have an old book with yellowing pages in it chances are that book is pretty old and the paper is going acidic now the same thing is happening inside these capacitors because these capacitors have paper and foil inside them now when the paper goes acidic it passes DC from one side to the other and that's a function that these capacitors are not supposed to do they're only supposed to pass AC and block DC so these capacitors here if you want to picture a fault condition you can put a resistor across this and that's really what's going on now I know a lot of audio guys seem to like these old Bumblebee capacitors thinking that they make their audio circuits sound better well they didn't sound like that when they came from the factory because they weren't leaky and really what these things do in an audio amplifier since they passed DC through it puts DC voltage a positive DC voltage on the grid of the next tube driving it into hard Class A driving that tube into hard Class A causes it to draw excessive current and burns out plate resistors and does all sorts of bad things in old receivers these things are responsible for destroying if' transformers and burning out power supplies and doing all sorts of things so if you have old bumblebees in any of your equipment be prepared to be repairing the power supply or you know replacing tubes on a pretty constant basis these things will read plate final tubes like the audio output tubes they put a positive bias on the grids of the say you had 6l sixes this would put a positive voltage on the grids and cause the 6l6 to read plate which in turn destroys the tube in short order again through excessive plate current draw they even burn out audio output transformers so these guys have got to go and usually they get replaced with polypropylene style capacitors like this all right the next capacitor we're going to look at here is a mica capacitor and they are very very stable capacitors so they're stable over a very wide temperature range and you'll find these capacitors in oscillators and precision RF circuits and things like that very rarely do these things fail so if you're tempted to replace the style in this particular style of capacitor what you want to do first is make sure that it is definitely faulty in that there is some sort of a problem with it in receivers many of these capacitors are hand picked and if you replace these capacitors you'll have a real hard time getting the dial accurate again this capacitor right here is another very dependable capacitor this is a ceramic style capacitor now you never ever want to put this style of capacitor in any kind of oscillator circuit but these things are very dependable they never seem to fail so you'll find these as RF bypassing capacitors and I'll refer to all this again on the whiteboard this is a polypropylene style capacitor and these are great in audio amplifiers and they're also very good for RF coupling and things like that again not good for any kind of stability in an RF oscillator or anything like that this is an NPO style capacitor and these are extremely stable in RF oscillators they work very very well and the capacitance moves very very little with temperature change and that's very crucial in an RF oscillator so these are very very accurate this here is a 1206 part with just some legs assaulted on to it so that we can do some experiments later this is another newer style mica capacitor so really that's this that are in a different style package that's all this is these here are orange drop capacitors and these are also newer style capacitors this is an orange drop and this is a brown drop capacitor they call them they are also very very stable and you'll have absolutely no problems with these things unless of course there's been some form of temperature damage or anything like that this capacitor here is a polystyrene capacitor and you'll see these things in a lot of the newer solid state equipment they use them in oscillating circuits in tuners and all that kind of stuff these are very very stable as well but they're not very good with external temperature so you can't heat these things up polystyrene is very very soft and if you heat these things up the capacitance will change and when it cools down it will stay at that so it kind of has a memory effect so these should be used in relatively cool circuits if you're using anything like this in a vacuum tube circuit you need to use a lot of thermal decoupling and keep these things away from tubes when you're soldering these things you don't want to have very much dwell time with your soldering iron on these legs again or you'll cause damage to this particular style of capacitor on the white board here I've got all sorts of different styles of capacitors listed what I'm going to do is work down the list here and explain a little bit about each different style of capacitor and I'll give you an idea of the circuits that you'll find these in also talked a little bit about some of the capacitors on here and tell you what circuits they should be used in and shouldn't be used in after I'm done explaining what's on the board here we're going to turn this into usable experience we're going to go over to the bench and I'm going to demonstrate how the capacitance of these capacitors changes with temperature and we'll also take a look at some vibration and see how the capacitors react to some vibration very important to understand if you're designing or repairing any kind of circuitry and you're looking to substitute a capacitor alright the first capacitor we're going to talk about here is the np0 style capacitor the reason i've got 0 and brackets here is because a lot of people say NPO it's actually NP 0 or C 0 G and this stands for negative positive 0 and these are extremely stable capacitors you'll find these capacitors in crystal oscillators variable frequency oscillators beat frequency oscillators and in RF coupling circuits so basically anywhere you find an NPO capacitor usually its RF related like the circuitry is RF related all right so the capacitance movement to temperature is positive negative 0 to 30 parts per million per degree C and their usable temperature is negative 55 degrees C to positive 125 degrees C so quite a usable range and very very stable the next capacitor down is the mica and it is also very very stable you'll also find it in the same kind of circuits that you find the NPO capacitor all right its accuracy really is positive negative 50 parts per million per degrees C so not as good as the NPO but very good so you'll find you know these are mica capacitors and a lot of older receivers those dominoes style capacitors that I talked about those are mica and some of the newer style mica capacitors they almost look like a little brown piece of gum with two legs coming out of them those are also a mica style capacitor and we'll also take a look at some of these over on the bench here and you'll see what I'm talking about all right very very good for RF service as well so Mike and NPO are kind of the top of the list for any kind of oscillating circuits or you know any kind of RF circuitry whatsoever polystyrene are okay stable and they are temperature temperature sensitive so polystyrene caps are those little kind of clear caps and you can see the foil wound inside and the ends kind of look like they've got a pattern on them with two leads sticking out you'll find them a lot in tuners and solid-state equipment so when I say okay stable they're not as stable as the NPO or the mic up but they are very temperature sensitive and I'm talking about external temperature sensitive so if you get the actual case of a polystyrene capacitor hot it will move in capacitance and then when it cools down it will stay there so it will keep moving if you keep getting it hot so what I'm trying to say is you don't want to tie polystyrene capacitors to any hot tube pins if you're soldering them you got to be very very careful because the soldering iron will again change the capacitance a little and when it cools off it will stay there it won't return all right so polystyrene caps again in a lot of solid-state equipment you very very rarely find them in anything vacuum tube and if they are they have quite a bit of thermal relief and they are far away from the vacuum tubes these capacitors here are ceramic style capacitors the x5r x7r y5v zedd five you are either those disks tile capacitors with a leg on each side or you'll find them as small chip capacitors for surface mount use okay the X is the lower temperature the five is the higher temperature all right in the R is the actual usable range I didn't have enough space to write the usable range in here but that's really how this coding goes now these capacitors are great for RF bypass you don't ever want to use them in any oscillator circuits alright any kind of tuned circuits RF coupling is okay from stage to stage as long as there really is no interlock between the stages and when I say interlock one stage will affect the other all right so that's really what you want to you know use this particular style of capacitor for RF bypass they work absolutely great I use them for our bypassing everywhere all right polypropylene caps are good for audio and RF stage coupling they're not very very stable nowhere near as stable as anything up here but they are great for audio polychrome caps you find them a lot in audio amplifiers and in some RF circuits as well they are okay for that no oscillating circuits again absolutely not oscillating circuits are pretty much NPO and mica capacitors and maybe sometimes polystyrene all right tantalum capacitors are horrible for audio they're nonlinear but they are great audio are great RF bypassing capacitor or timing capacitors so if you're making a circuit with a 555 timer or something like that and you need some sort of stability you don't want anything to move around tamerlan's are great because they go above a micro farad quite easily and they are pretty temperature stable all right paper again no good if you find any paper caps and anything old you want to get rid of them there are some new paper and oil capacitors that are maybe ok some of the audio guys really like that kind of stuff but any kind of old paper capacitor you want to just get rid of so whether it's a bumblebee or a black beauty or just a regular you know foil paper style capacitor in the trash they go and replace them with a polypropylene style capacitor and that's really what's on this board here so what I'm going to do now is take the information that I've shown you hear and we'll go over to the bench and I'll demonstrate this with a capacitance meter an oscilloscope and some other tools what I've got set up here is a mica capacitor in the test leads of my capacitor tester this is just a drill vise holding them steady so this is our little test jig for now right here you'll see a green clip that's just an attempt to keep noise off the actual drill vise itself so now what I'm going to do is I'm going to take my hot air tool alright and I'm going to heat this thing up now I'm not going to take any temperature measurements of the actual capacitor itself our temperature measurement for today is screaming hot so basically you can picture this thing strapped to the side of a 10 watt resistor so I'm going to heat this thing up very very hot and we're going to see how much it actually moves in capacitance now of course this is going to get way way hotter than it would actually get in real service but still in a worst case scenario we can get an idea of how much this mica capacitor is going to move so I'll move you over here to the capacitor tester all right so really all we're going to be paying attention to is you know maybe these digits here at maximum this here is really just you know random air current moving over that capacitor at this point and maybe some noise mixed in there as well so we're at ninety six point three six eight picofarad and even if I move my hand close to it here I'll just put my hand close to it you can see how much it alters what we're seeing on the capacitor tester here so when I move the actual hot air tool in front of it you're going to see the digits go all crazy here but in the end we'll have a reading here so I'll give you an example I'll turn this thing on right now so let my my hotter tool get nice and hot so we're at ninety six point three six something like that Pico farad all right this hot air tool is already hot enough to melt solder so what I'm going to do is I'm going to bring the hotter to a close to the actual device under test and I'm going to heat it up so we'll keep a keep in mind here ninety six point three six so here we go okay so that's screaming hot I move the tool away so now we can get an accurate reading so from ninety six point three six to ninety six point five and as you can see it's coming down rather quickly so we have maybe point two of a Pico farad movement there still ninety six Pico farad so we haven't even moved one Pico farad that's pretty good just turn that off so maybe point two of movement there very very stable excellent for oscillator service these things and of course again we've made this thing you know way hotter than it would actually get in real service here and as you can see it's coming down to room temperature and it's coming back alright so I'll remove that from the test fixture now I'll put this NPO capacitor in here that we looked at on the piece of paper earlier it's that 1206 part and I'll just put that in here okay let everything settle down here for a second so at 101 Pico farad 0.47 okay so I'll turn the tool back on here again keep in mind when I get the tool close to it it's going to get all crazy because of the noise so 101.4 seven I'll heat this up move it away so on a 1.5 you can see how quickly that returns now that was almost hot enough to D solder the leads off that part all right so very very stable component here we go right back at 101 point four seven again so extremely stable part excellent for oscillators so now what I'm going to do is I'm going to show you the opposite end of the spectrum here I'll remove this thing and I'll demonstrate just a standard ceramic capacitor like you see right here all right standard ceramic okay so it's in the vise I got my hands off of it and as you can see it is still moving and that's just because the heat of my fingers is settling off now into the test fixture all right this is supposed to be 103 or point zero one micro farad and we're coming up to that there we go okay now what I'm going to do is turn on the tool again and I'll just swipe this across the face of this capacitor a few times now this would be Oh opponent to Zed five you or something like that something yeah Zed five you would be close enough there is no actual rating on this so it's probably like I said five you said five be something like that here we go I'm gonna heat this thing up so now we're at point zero zero two micro farad point zero zero three point zero zero four as it's cooling down point zero zero five and so on you can see it counting up point zero zero seven point zero zero eight so now just think if you put one of these ceramic capacitors inside of say a vfo or any you know sensitive oscillator that oscillator would move all over the place and it would be uncontrollable just even slight chassis temperature changes would cause this thing to move right so I'll just touch it with my finger it's still climbing okay that's just holding it with my fingers let go of it incredible amounts of movement in these ceramic capacitors so definitely no good for audio as well because they have a thing called the piezoelectric effect and they become quite microphonic in audio service and I will show you an example of that here so ceramic capacitors you know like this here or the like should not be in any kind of audio signal path again great for you know RF decoupling or RF bypass service but um even at that you know I wouldn't I wouldn't try to have this thing in any kind of a signal path other than to you know drain our after ground really all right so now what I'll do is I'll put this capacitor in here it's polypro cap alright I'll put it in there this one is rated point one micro farad okay it's in the test fixture there we go pretty close so now what I'm going to do is apply a bit of heat to this now again I keep in mind that this is a polypropylene cap so I really don't want to heat this too hot or damage the unit but you know I'll heat it to the point to where it would you know get warm and service all right so that would be about the temperature would get in service look at that no problems at all as you can see a lot more stable than the other capacitor way way way more stable all right and grab it here with my fingers as you can see as I put my fingers on it very stable that was me moving it in the vise they're very very stable capacitors so great for audio and stuff like that that really is the three capacitors of interest here actually I could go grab a tantalum as well I'll go grab a tantalum it will be right back I have a dipped tantalum capacitor in the Vice here I'm sure we have lots of interesting horror stories about dipped alum capacitors if you got some let's hear about them so anyways what I'm going to do is I'll heat this and we'll take a look at the gen right here again alright so we're at about 4.7 micro farad we're not going to really get too much more particular than that so they're all this is it an NGO style capacitor anything so I'm heating the tool up here again and I'll run it across here just a couple of times and that would be blazing hot right now four point seven nine not too bad not bad at all so you can see these are relatively stable they're good in timing circuits and things like that of course I've heated this thing way hotter than it would ever get in service but still gives you an idea of how much they really move especially when they get screaming hot for this next demonstration I'm going to use this Tektronix type 547 oscilloscope with this high gain plugin so right now I've got this calibrated to show 500 micro volts per division on the screen what I'm going to do is take this ceramic capacitor I'm going to put it on the front here this is a point 1 micro farad capacitor it's a Zed 5 V style and I'm going to tap it ever so slightly with this insulated rod right here the noise you see on the screen of the oscilloscope right now is from me I'm standing about three feet away from the oscilloscope and just that capacitor poking out of the front is acting as an antenna picking me up and a little bit of the tripod and camera as well so what I'm going to do is touch the face of the oscilloscope and that will ground my body out a little bit keep that interference down just a bit if I was to ground the tripod out it probably almost get a nice clean trace so now what I'm going to do is I'm going to tap this capacitor with this rod and watch what happens on the screen when you see the trace moving up and down like that don't pay any attention to that that's just my hand moving here that's how sensitive this is but you'll see another effect here in just a moment so here I go see all that there how it's going below the line that's creating voltage when I'm tapping this capacitor and that's called a piezoelectric effect and that's why these capacitors here are absolutely no good in audio amplifiers or in any kind of high vibration atmosphere so just think if this was in an amplifier on the stage of an auditorium and it was very very loud and this was leaning up against the chassis and just ever so slightly buzzing the amount of noise that this would create into the circuit would be absolutely incredible so from the trace deflected downwards we had from what I could see about 1.5 to 2 millivolts worth of you know spikes there it was exceeding the graticule just a little bit there on one or two of little bumps and I'm just ever so slightly tapping that so it's creating quite a bit of voltage alright so what I'll do now is I'll plug in this polypropylene capacitor and we'll see what it does so again I'll get rid of some of that hum now I'm going to tap this here again don't pay any attention to that bobbing of the trace that you see there that's just me moving my hand up and down so when I'm tapping it that's just the movement of my hand as you can see so again we're just looking for those spikes so here I go as you can see absolutely no spikes there whatsoever and I'm hitting this actually pretty hard and that's why polypropylene capacitors are great for audio amplifiers and high vibration atmosphere because they don't have any of that piezoelectric effect now again these other capacitors are great for RF bypassing these ones here are great for RF bypassing but in a low vibration environment again I hope you found the information in this tech tips Tuesday useful if you did you can let me know by giving me a big thumbs up and hang around there will be many more videos just like this in the very near future touching on all sorts of different topics related to electronics so until that time take care bye for now you

Channel: Mr Carlson's Lab

Views: 798,318

Rating: 4.9419813 out of 5

Keywords: Creative Design Components, creativedesigncomponents.com, NP0 capacitor, C0G capacitor, poly capacitor, disc capacitor, mica capacitor, polystyrene capacitor, black beauty capacitor, bumblebee capacitor, understand capacitors, piezo effect

Id: 67M7fsbLUIU

Length: 24min 3sec (1443 seconds)

Published: Wed Feb 17 2016