Tony - I really appreciate you taking time to do this analysis. I’ve had others suggest I do the same, but I never got around to it. I agree with you on the physical size of today’s caps vs. the vintage and the impact it has on potential noise. As others stated, I think lead dressing has more effect and can influence the results/performance. I did notice the lower cap values were hard to discern the outside foil while the larger cap values (physically larger too) were easy to identify and the ingress/egress I measured was more pronounced. Thanks again for the mention and again great job putting this together; I know it was time consuming. All the best. Don
I used to work for Magnavox back in the day, as part of the design team for the Odyssey II. An engineer there had a high end television on his workbench to test various configurations. The janitors would take their midnight .00221break there and eat lunch, leaving crumbs all over. He left notes (he didn't care if they watched TV, he just wanted a clean bench), began to turn off the bench at night so they couldn't turn on the TV, but they quickly figured out where the bench switch was. FInally, one night after he turned of his bench, he got the biggest electrolytic cap he could find, and plugged it in with alligator clips. The next morning, there was tin foil everywhere, and no one ever used his bench again after hours.
I use to build Distortion Pedals for my Guitar setup and I found you need the foil side to be on the correct side or the pedal would pickup a wide assortment of noise if you don't touch the strings. Speaking of Distortion Pedals you can use one and a Guitar Amp to find the Foil Side of a cap. Put Alligator clips on an old patch cable and touch the Cap's body. If you touch it and it induces noise then try turning it around. The quieter side is the Foil Side. Also I'm a odd ball, If I use a Transformer for a project I make sure to toss a scope on to find the correct phase/rise of the sine wave to use as the Positive. Safety Caps on any circuit that touches chassis ground if Earth or Neutral is attached to the chassis. I guess I attend to over engineer things.
if over engineering things makes them more rebust and last longerthen in my opinion that means fewer breakdowns in the event of rough usage such as shipping, moving...etc... that means a quality product..unlike the way things are built and handled today visa vie shipping.. nothing worse than buying something to have it last a short time and to have to replace it cause of only using components that are made with flimsy materials... people will pay alittle more for quality.. over engineer all the time..thats my belief..cheers
Mr. Carlson's Lab has done several videos on this topic. The idea is the foil side should attach to the lowest *impedance* side of the circuit, not necessarily the lowest *voltage* !
In some old German radios you can also find caps with 3 leads. Those have an additional outer foil connected to the 3rd lead that is then soldered to ground. You make some really good points about size and the question is if it would make a difference to wrap one of those modern caps in foil and connect it to ground. I say, just like you, that it can't hurt to do it, if that's how that particular radio was designed. So, I use self adhesive copper foil and solder a 3rd lead to it. Another point that you did not mention is the fact that caps are so much cheaper today so people use higher voltage rated caps to replace the old ones. I some cases the new cap ends up being almost the same size as the old cap that was rated for a much lower voltage. So perhaps that's another scenario that needs to be looked at separately. Lastly, I think it's not definitive to do one single test. As you said yourself, you did not get all the answers from that one test. So, what might be the conclusion of one test might not apply to another circuit. That's why scientists need tons of data to draw solid conclusions. I think it's great that you took the time to do this. You got my thumb's up.
This video helped put my mind at ease with regard to a current project I’m working on and didn’t pay attention to the foil ends which weren’t indicated. Thank you!
Another great thought provoking video Tony. I think you discovered, what I have often thought, that for most coupling and de-coupling applications it does not make much difference which way round a capacitor is connected, it is simply good practice on the basis "if you can - why not". All the contributors to this topic on RU-vid focus on noise pickup, which in your experiment proved un-measurable. Where outside foil connection might be important is in circuits where the capacitor is used to determine frequency e.g a Wien bridge oscillator. In such an oscillator if the outside foil is grounded then squeezing it should have little effect, however if the outside foil is connected to the grid, gate, base of the active component a quick squeeze could have a marked effect on the oscillator frequency - maybe an idea for your next experiment?
You have achieved the near impossible by explaining capacitor foils in easy to understand language; thank you. After reading the comments people have added to this video it seems most agree with your comment, save a few die hards. The one comment that really hit home was the capacitor size e.g. the old caps had a large surface areas and hece would attract more RF than a 1206 1.5 mm equivalent. A 1206 capacitor is 1.5mm wide and is often the same width as the trace its attached to and thus would attract almost the same amount of RF as the trace itself.
Interesting. After many years in the industry and after viewing the videos that discuss this topic it is clear to me that AC circuit operation hasn't lost its mystery. Eliminating excess noise and hum is still a black art that most people don't fully understand, myself included. That mystery is part of the attraction of electronics for me -- also its frustration. My feeling is that following the outside foil rule is such a simple process. It may help a lot, or not at all, but in all cases it couldn't hurt, and it takes very little time so that alone makes it worth doing. Hunting down odd noise problems can be frustrating. If following this rule can reduce that frustration and provide some peace of mind, then it will have been time well spent.
Even worse these days with all the noise sources in a typical household - switch-mode power supplies are all over the place these days, and tend to spray a lot of RF noise, both through the air and via the power lines.
Thanks Tony great video. I restore old radios as a hobby. When I first started and learned about the outside foil situation I started testing all caps before installing them. What I have found is that the choice of the replacement capacitor (type and mfg) can have an impact on the noise seen on a scope. I've tested some capacitors that show a lot of noise when tested in one direction verses the other. I've also tested some of different style and manufacturer that showed almost no difference and very low noise no matter which way they are to be installed. So in the end I now just stick to those caps which show very little noise no matter which way they are oriented. They may not look "original" but they sound just fine.
I recommend you do your own tests and form your own opinions. I'm not interested in adding to controversy by recommending components or suppliers and I think more can be learned by testing for your self. Who knows, the perfection you seek may be over the top for some people and not far enough for others.
xraytonyb , what a great benefit you have managed with your two bit analysis... golly, common sense is not always around any more thanks to people like you.
I'm glad that you finally got around to doing a test on this subject,I've heard you talk about it a few times,d what you've found out is what I've thought all along,. it might make a difference with those huge caps that they used back in the 1930's but not so much nowadays.the old time techs knew what they were talking about when they told you it didnt matter any more
Hi Tony, thanks for your time to create the great video. I agree with you that this really depends on the overall circuit and the packaging of the components. Another point is the capacitance. Caps like 0.1uF for example have a much lower AC resistance than smaller ones like ,0.01uF for example . The smaller cap is then much more sensitive for putting it in circuit backwards. Many caps are just RF bypass caps to ground. Those are low impedance to b+ and also to ground. For those it really doesn't matter I would say. Coupling caps may be a different story.
It might be interesting to try the same experiment using the original, "old style" caps...to get an idea of what the "old guys" were talking about when they said the newer caps were "better". Also, if you think of the outer foil being an "antenna", size and resonant frequency may play a part.
its a good idea to replace all the old wax paper caps. a quick check with a dc dvm. many of them are putting out a dc voltage because they are corroded to the point of becoming batteries. obviously that is fatal. back about 20 years ago a fellow employee asked me to look over a 1930 ac table radio. we live where its dry. someone had replaced the electrolytic caps but the wax paper caps were original. I warmed the radio up completely and tested for any leakage problems etc. they all worked fine so I just let it go on working.
Nice old Tek 485. I bought one for $45 on eBay last year. Channel 2 vertical attenuation board had a bad switch. Found a full board around January NOS a guy had for sale. Cost $50 but for a little over a $100 I have a great old 350Mhz scope that works prefect. A few weeks after I found the 485 I got a perfectly working Tek 2430A for $50 with 10x probes. Was my lucky year. Made best offers on both and got them. I’ve run modern caps both ways and never notice any major changes. I usually mark them but sometimes just slap in a replacement in a radio or guitar amp. Test equipment I always make sure to check. Some caps you can’t see a difference.
Oh dear, you're debunking some deeply held myths here. The greybeards are going to blow a fuse or two. Next you'll be claiming that they don't need $10,000.00 speaker cables. :)
My two penneth is that this comes under the heading of "Good Practice". You can knock nails in straight or slightly crooked, they still hold. In many cases the outer foil may be irrelevant but then what if it's not and in some cases it does actually matter? My view is if you are able and willing to determine the outer foil then you might as well do it and mount the caps according to that. I have fitted thousands of caps in circuits and rarely bothered with the outer foil but then some of my radios hum. I don't know if they hum because of my bad practice or because they just happen to hum due to design issues. Tony's experience with his radio here may be typical but I was surprised at the results.
Won't matter a LICK with modern caps unless you just have bad lead dress. Can't tell you how many dudes have sent me that Mr. Carlson video link and I've had to tell them only really REALLY persnickety people will care about the foil orientation in 99.9% of all situations. You will not detect a difference in modern caps because the sizes of the caps are so tiny, they aren't much more conducive to RF than the bare leads or traces leading up to them.
Very informative, well done. I got a lot out of this. This was easy to listen to and steeped with sound electrical engineering principles, thought and discussion.
Nice video Tony. I would have been rather surprised if the results had been any different. I do still mark the outside foil end of capacitors when I buy and stock them so I don't need to do it as I use them. I do not pay much attention to their orientation when installing them for audio work, BC band radios, or power supplies. However I did a test very similar to yours but in a communications grade receiver that operates in the 25 to 30 MHz range. I can assure you I found very different results when testing at that elevated frequency, as much as 10 dB in some receiver chassis designs.. I still restore BC radios, although less often then 20 years ago, and if working on a model that includes one of more shortwave bands I make sure to install the cap with the outside foil to the low impedance part of the circuit.
The one time I had trouble with "outside foil" was in the RF front end of a AA6. The new cap totally messed up tuning a clear signal. Detuning the set helped a little but was not wanted. I replaced the new cap with an old but good cap with the marked lead and all the trouble disappeared. Pulling that and reinstalling the new cap in the opposite direction gave far better results than the first time. I didn't trust it to hand it to a customer so I relocated the cap to another physical location but now watch out for this issue. It may only be an issue with AA6 designs with their RF amplified front ends. Never had an issue in audio stages though. It may be a frequency thing. Higher frequencies can get into more things in a radio than audio. Haven't had occasion to try it with a tube hi-fi preamp. It has been noted that it seems to be impedance-related, solid state circuits not giving a fig.
Depends on the solid-state device - BJTs don't care much, but JFETs/MOSFETs are likely to be sensitive due to their considerably higher input impedance, much like tubes.
Ya thats what I come to conclusion two! It depends on sensitivity of the circuit, its frequency, of many other variables! In some circuit it may not do any difference, and in other make a noticeable difference or even creat oscillations! In any case this is a great learning video good job on explaining some of the conclusions. In the future it could be interesting to see what difference it dose in a really sensitive circuit?
Thank you for taking the time to post this video and all the time and thought you put into it. If the outer foil side was so important the manufacturer would mark it on them. The biggest thing about it that is so often over looked is the fact that we are talking about capacitors, not shielded cables. The job of coupling caps and bypass caps is to block DC voltage but act like a wire (or short circuit) to pass AC signals. With that in mind the only difference would be in the efficiency rating of the capacitors to pass the AC signal which is very high in todays capacitors. When Mr. Carlson demonstrates it he is acting and testing a cap as if it was a coaxial cable which has caused a lot of confusion to those who have not been properly schooled in electronics.
Good point made !! Good video as always!! I think the outside foil thing is more relevant in high quality audio amps and or high stability high accuracy rf oscillator circuits but I do observe the fact that in old design practice the outside foil goes to ground or lowest impedance part of the circuit, but that's my opinion only. great video though enjoyed it much!!
Paul Carlson is stomping around punching walls after watching this! Seriously, this was very interesting. I thought for sure you would see at least a little decrease in the noise. I think you are correct in about everything you speculated here.
It's somewhat erroneous anyhow because your body is acting like a fractal antenna, and your fingers are capacitively coupling whatever RF noise your body picks up directly into the body of the capacitor. Under a tube radio chassis, made out of steel, most of the noise you are going to get is junk coming down the power line from badly designed switch mode supplies. I think that lead dress matters more then which way a non polarized cap is installed, such as you want to route AC wiring, such as for the tube filaments, away from the audio amplifier stages as much as possible. I actually fixed an AC/DC radio where they failed to do this with the volume control wiring, it had a low level 60 CPS hum present until I re-routed the heater wiring, it ran parallel to the top end of the volume control.
What I have picked up on this subject is that (especially) in high impedence (Tube) gear you want to connect the outside foil to the point with lowest resistance, often the anode or cathode, to minimise the chance of noise and hum being introduced in the circuit. And this makes perfectly sense to me. Might have been interesting if you could also have done the test filtered to only look at the line frequency (I believe it's 60 Hz where you are, where I am it is 50 Hz)
Yeah the argument about 'they did it that way partially to prevent accidental shock if the capacitor was accidentally cut and you touched it' doesn't make sense. There's dozens of places you could poke your finger in the chassis and get shocked. Now it would be a different story if the exposed cut touched something else in the chassis, but the paper tube casing on those old caps is relatively tough to begin with (unless they explode!) I mean sure it could prevent shock in this scenario but doesn't sound like something the factories would be concerned with.
and im here from an audio channel where they're also wrapping the capacitors in copper foil 😂 to shield the shield. not any copper foil mind you, no this is the 100% purity single crystal .....bog standard adhesive copper tape.😂 someones making a lot of money off these people. best one is where the guy very delicatly wraps an entire cap, leads and all, in copper foil, like an oldschool candy (making the most of that very expensive cap by shorting it completely😂) but it was done with so much care and attention.
I think this falls into a "do it this way and you'll minimize your problems". Sort of like insulating component leads that go past other connections to insure they don't short.
Mr. Carlson spends an awful lot of time talking about this. He demonstrates it quite clearly every time. He also designed a device to show you which end is which on modern caps. (edit: I see you are aware of this and mentioned it in the video)
You made the same point I've always made about this ridiculous controversy. I have never run into a real world situation where orienting a modern capacitor according to these "tests" results in better measurable (much less audible) performance in the actual circuit. Orientation would only have potential impact in audio coupling applications, but even here, most of the radiated energy getting into the cap would still be shunted to ground one way or another through the coupling action of the capacitor itself. It really is a non issue.
@@timka880057 Indeed, when I got home from Vietnam, I went on sick call for the damn ring in my ears. Doc said I had "tinnitus, or what I like to call Vietnamitus" still have it, only now it is accompanied by hearing loss. Sure glad I went on sick call that day, it streamlined my disability so the VA furnishes me with hearing aides and needed supplies.
I just replaced mylar capacitors in my nikko trm-650 amplifier with poly-caps, cause when i did that on the tone control board, cause not much of the lower frequencies seemed to get through (plus some resistor value change to the resistors going to ground for the base control) i noticed that the sound was much cleaner, less harsh sounding. on those new poly-caps, i tried to find the outer foil with my digital, usb oscilloscope, but that was less than easy. finding a "quiet" room where the noise from all the electrical appliances isnt drowning out what you induce touching the capacitor is quite a task. And maybe the digital oscilloscope i used wasn't quite up to the task either. Just holding up the capacitor connected to the oscilloscope raised the noise floor like crazy, heh.Anyways, i think i found the outside foil and it kinda makes me feel better. The amplifier never was noisy; it's dead quiet even with the volume way up, but like You said, it either doesn't matter or finding the outside foil will make the amplifier even better. I think it's worth the extra effort ^_^ Thank You for the video and for giving us something to think about ^_^
I have been tinkering with these digital scopes, you know the cheap build kits. I have two kits one small the other larger, both I purchased with case. I find the larger of the two easier to read and use, the pocket model works, well it does now after I screwed with it for a year only to discover the rotary encoder they included didn't work, and was giving me all sorts of problem. Then one day I found a youtube video of a fellow who built his own from an Arduino, it's just a tiny little guy, fits in an Altoids box and uses a 0.96 screen but you know what, for finding outside foil it's the real deal! I also built a box to allow me to use the downloadable soundcard oscilloscope software, that to works fairly good but you have to contend with the noise from the computer driving it all. To cut the noise, I picked up a USB sound card that I channel it through, and that makes it work much better. The scope box includes two 7805 regulators to keep the voltage of the circuit tested safe for input through the USB and soundcard as well as some diodes and a couple resistors. It all fits in a small build box that I picked up off Ebay.
Very interesting. I have been fortunate to not run into problems relating to capacitor orientation. I can agree that there might be cases where it does matter. In fact, there are some circuit designs where wire dress matters, a lot. You can wind up with motor boating and other funky problems. I would expect that you could have issues in those circuits related to capacitor orientation. I am wondering if I should pay more attention to this. Not really sure though. I will keep this in mind if I run into an odd problem in the future.
I have also done the tests on "finger noise coupling" with often small difference in the cap orientation (at least on new Poly caps) It could matter in very high gain circuits, with e.g. heater AC leads running close to the cap, or a high level output lead running close to it causing feedback. Again, as you said, not a good component layout. I usually do not take the time finding the outer foil..
I have wondered about the newer capacitors, Cornell Dubilier has some really small axial film polypropylene caps, rates 100- 630 volts dc or higher, I haven't tried them yet, I usually use ones from Antique Electronic supply, the yellow exterior film, like you've shown here. What do you think about these smaller ones for tube gear? And do you think it would matter which end to solder into the circuit??
This right is up there with JohnAudioTech's video on damping factor. Great job! My guess is that the surface area of the outside foil has more to do with it than anything else. A 2" long 7/8" diameter cap is 5 1/2 sq. in. A 3/4" long 3/8" diameter cap is 7/8 sq.in. That's about 1/6 the area. The wavelength of the noise may matter (it does on antennas). This caused me to do a thought experiment. If a magnetic field passes through a cap, does it cause noise that cancels out like a balanced line? I'm flummoxed.
That's the thing - for the same voltage rating, modern dielectrics like polyester and polypropylene are much thinner than the oiled/waxed paper of vintage caps. Since capacitance is directly related to the distance between the plates, the thinner the dielectric the higher the capacitance per unit area, and thus modern caps are much smaller for the same capacitance.
You measure this noise over small bandwidth of AM receiver ( mixer +LO), which in this case hum noise (60 or 50 Hz) is far below 900khz , But if you have wideband amplifier from DC to 100MHz ( like oscilloscope) you could see it ,
When I re-cap a radio, I do them one at a time and try the radio. If a new noise shows up I reverse the cap. Sometimes the noise goes away and sometimes it does not. But new caps are way better than the old paper wax type.
I been working on tube radios for about five years,been collecting equipment for that long ,but I tried to check out out side foil with my tiny oscilloscope eso 188 model that when I found out its limitations until I can come up with a better scope someday ,do you need to find out the outside foil for every appication.,I most repair 60,s era radios.to learn on so far no problems ,but as now I don't have away to detect outside coils unless my fluke can?
In my experience of some 40 years I have never seen any difference as to which way the cap is installed in your standard radio restorations. More important is the lead dress. Mr Carlson started this some time back and of course some believe it as gospel truth. Not in my experience. Modern caps won't test on a scope using his method unless they are of a certain value and voltage rating. Some are wound internally and the outer foil does not have a connection to either lead. In short don't worry about it.
First in most cases the capacitors are mounted in a metal frame which should provide significant shielding from outside signal sources. (Although the electrical noise environment today with prevalent switch mode power supplies and PWM controls is arguably much worse than the past). I think the main concern about the outside foil is the proximity between components. Under that assumption, the outside foil side is probably much less important compared to just paying attention to where wires and components are located in the circuit. Most spurious signal sources will be coming from the wires inside of the circuit, some of which such as filament wires will be significant source of hum noise. Being careful about how the wiring is arranged in the chassis is probably the most important aspect.
I am pretty much confined to my recliner, following an accident when I was a cop back in 1993. I have a PC beside me that I have set up as a media server for the house, and a laptop that my good wife of 50 years gave me last Christmas on my lap most of t he day. I also have all sorts of Arduinos and ESP32's set up for different purposes and, of course many of them run off switch mode power supplies.I do work on old radios, if they are small enough to sit on my lap. What I have found is that my lap is a bad place to try and test any sort of radio as the electrical noise around my chair is so great that nothing, other then my old police scanner can receive any active signals in the area.
I recall watching a video a few years back where a fellow used a couple of rolls of household foil and household waxpaper to roll his own capacitors, then stuck the whole roll inside a PCB Pipe with terminals on each end. He came up with capacitors that could kill if abused, at least this was his claim.
Hey nice video! You mentioned and briefly showed a small device you got on eBay that can do this check. I searched eBay but could not find anything. Could you post a link to what you found? Thanks again.
I have been working on equipment like you are showing here for 60 years. do I worry about which way a capacitor goes in. mostly no. sometimes it does matter a little so its ok to put them in the correct way if it makes you feel better about it.
Ah! The feel better factor. Also gives the next techie and excuse to moan about the previous techie by saying, "the last tech put half of the capacitors in the wrong way round". Then overcharge the customer by telling him that both the old and new capacitors had to be tested for orientation and that took hours. Agree in most cases makes no or little difference, unless you put your device next to a strong source of RF.
Perhaps if the measurement was performed with a FFT spectrum analyzer the results would be different. In this experiment the total of the output power was measured.
They were actually a fairly inexpensive set I got from Amazon, I think. I don't remember the cost, but they were under $40. They are pretty good quality, but no name, just generic.
They look really similar to the BK Precision set that I have for my 880 LCR meter. www.techedu.com/Kelvin-Test-Leads/BK-TLDK1/ The ones I have are the TL8KC1 though.
Tony , I think you should have serious talk with your wife to take your lab to bigger room , we as viewer have some rights to follow all these wire easily. Mr Carlson lab is bigger too.
I think it might be a better experiment to pick a topology such as a bjt common emitter amplifier circuit, where the cap under test limits the upper end frequency response by shunting the base signal to ground. Then employ a nearby noise source (a narrowband signal ) in the frequency band the capacitor is supposed to reject, and see if the cap orientation changes the high frequency noise rejection? That would better discern the difference this might make in a worst case application?
Ok, you put the outside foil all in one direction or the other. What would happen if you put the capacitors in randomly? I put them in my radios and they play great.
Your tests and explanations are very instructive, but they also prove many so called specialists and particularly audiophiles ones still have something to talk about, as the "new" capacitors can proof or not "orientation" sensitive. And you perfectly point the problem: keeping the orientation of the original design is always good, as it cannot "at least" make the things work worst. Anyway, the rules you give are a good remainder for new designs, as some weirdest components for audiophiles could still use "vintage" technologies, like paper foils and wax, or some equivalent. I've seen Russian very strange metallic caps with glass isolators, very sought after "mustard" caps (guitar amps) and NOS components used to "sound" like vintage material... At this point, you always find fools! Last but not least, resistors have also their own thing about noise, and not solely as some power ones may sometimes get inductive in HF domains, but also as the materials (metal oxydes) used nowadays differ from the early carbon stuff. Modern resistors are also less temperature sensitive... Here you probably also find some good source for an informative video (and entertainment!) and what I call "scratching powder" for any audiophile.
Mr.Carlson did explain why they don’t mark them any more. It’s do to with the PCB board, and how they can design them. They can add ground plain under the components. Ether way you look at it, it does matter especially AT RF Frequency! But from what I’ve seen even at low frequency it can still get coupled at that point it’s about the capacitance. You mentioned RestoreOldRadios. He has several videos showing different methods finding the outer foil, one of many methods was injecting the signal into the capacitor, and using a signal tracer to determine the outer foil. If you noticed the capacitance can drop the signal making it hard to hear! Now looking at this bring me even more knowledge! This is a great experiment, and shows it’s still true even though the measurements didn’t show it. The only reason it didn’t measure is exactly do to the type of capacitor old .vs new! If you really think about it a capacitor is also an inductor, and the size of it determines its effects with RF coupling! Which is weird things began to happen because at one frequency it will couple very well, and others not show much, and is dependent on size. This leaves me to believe that the older paper foil caps pick up RF a lot better do to there size. And since the modern tubular caps are much smaller they would require a much higher signal in order to conduct enough signal to make it noticeable. I still think when you flipped them it still effected the circuit just not measure able. Also how the are made as well how they coat the dielectric with a thin metal film spray. I feel that would largely effect the inductance as well. So not just purely in its size it’s self, but also the methods and how they are made! Great video! Dropping a sub!
In the experiments where there was a noticeable difference in measured values of noise, can a extra shield like a box arround the capacitor(s) or closed metal chassis with ground connected (Farraday cage), eliminate the difference in noise ? I guess that some developers of electronic gear are aware of this effect, but ignore it and use decent shielding to eliminate it. I also think, that not every circuit is the same, and that i can mathers in some circuits like audiogear, signal measurements etc, but in other circuits like a simple light dimmer, it doesn't mather at all.
I'm wondering here if the fact of the chassis to be a faraday cage may influence the test, attenuating eventual noise that may come from outside the chassis. Maybe a test with an exposed PCB may show different results, don't it?
My thoughts exactly Thiago. Although in a valve radio you'd think heater wires might induce 60 cycle hum, the problem interference may be high freqency parasitics or RF? Also the reversed caps in the radio were mainly coupling caps. A healthy coupling cap blocks hundreds of volts DC but for the low voltage AC signal the difference in induction and the loss between driven stages is relatively small. Unlike in a tone control circuit where a capacitor connects the AC signal to ground potential, shedding a significant percentage of signal. Weak interference mixes with a weak signal, then gets amplified. The tone capacitor in electric guitar wiring is said to be (occasionally) very orientation sensitive. Supposedly tone quality and responsiveness can be deadened appreciably. Many guitar electrics cavities are un-shielded. The pickups put out a tiny AC voltage. From this weak signal the tone cap cuts certain frequencies by running the pickup signal through a simple RC filter (a voltage divider), then to ground. The tone caps are always in circuit regardless of the tone pot setting. If the tone cap is picking up tiny amounts of interference or parasitics, the weakened AC signal is easily compromised. For shielded guitars it may not matter how the caps are oriented, Or the effect really is so small it's not a problem? Another brilliant and thought provoking video Tony, thanks again.
Hi Tony, What probes do you have hooked up to your Keithley 197? It seems to be a really nice shielded cable, but we can't see where it goes.. Cheers Mark
I get a lot of comments about those. I got them on eBay several years ago. They were actually a low cost no-name set (made of fine china, of course). I never expected them to be that good, but they turned out to be very good quality. I haven't seen them listed lately and I wish I had purchased a spare set.
@@xraytonyb Hi Tony, Thanks for the quick answer. Would be nice to see a quick demo, perhaps on your next random video. Or perhaps you did that in an older video? I don’t recall seeing them before. I’m really enjoying all your videos, and lately I’ve started going back to some of your earlier stuff. Cheers Mark
Hi. I am just a person with electronics as a hobby and i am not an electronic engineer, but i have this idea that in the old days when every apparatus was so big, and all was point to point connected, all the components where very unstable to interference from the outside like noise and magnetic fields. Every component has some electric field around it wich can be altered by a strange object near it. making the outside foil shielding would make sense to me in those machines. With the modern equipment like smd or some larger print material , all the conponents are so small and directly soldered to the print material, that to my openion it doesnt make any difference anymore how its components are installed. there are no long leads anymore between the components, and some components i wonder if you still can determ what the outside foil side is on a capacitor for on board mounting like smd modules. but thats my idea of the modern technologie .
Actually yes. Every device with current have a electrical field and a magnetic field. Modern stuff like smartphones not have a lot of issues because they operate with 5v most of time and they are digital and digital stuff have a lot of mechanism in the logical behavior of boolean algebra to stop errors by external noise. Also have most of time a metal shield. Analog electronics are more susceptible to noise and interference. One of the why most modern equipment works in the digital realm.
The foil on the outside acts like shielding. if that goes to the lower impedance side of the circuit (usually ground). They knew that decades ago. Less chance of interstage crosstalk, interstage oscillations, and hum. Mr Carlson's Lab channel would be the best source of choice. The man isn't just an engineer, but he is an engineer that, as a job, reverse engineers equipment. The man obviously knows more than 20 technicians put together. I would venture to say he is a genius. He designs his own test equipment etc. While his hobby is tube equipment, he can fix anything you throw at him. The nicest thing about him is he is a great teacher. While I like you Tony, I believe Paul Carlson could teach us all a thing or two.
I’m a bit skeptical about the outer foil argument for orientation but i think your test is not valid if the automatic gain control is not turned off since that will try to keep the signal amplitude constant.
Great video, Tony. On a side note, I can't understand why Black beauty caps are so sought after. Talk about severe leakage! I wonder if people care more about polarity rather than a poorly biased grid for audio coupling applications or RF bypassing....Your reactance, audience!
What's the big fuss about the outside foil? I think Mr. Carlson started this whole thing. In practically all his videos he brings out his "outside foil tester" and tries to sell the schematic on patreon. It's free publicity for him. Glasslinger , a genius if you ask me, laughs at him and his outside foil on one of his videos. Glasslinger doesn't bother himself with the outside foil when he fixes old radios so why should we?
Excellent points. I'd also like to point out that most modern caps do not have outside foil at all. They are made of stacked layers like a sandwich not a roll.
I would say, as less the parasitic capacitance to the environment and as more the capacitance of the capacitor itself, as less you will get a difference by swapping it around. And the capacitance of those old style paper caps in relation to the parasitic capacitance is already large. Capacitor eg. 22 nano farad and parasitic capacitance a few Pico farad. If the circuit gets in bad behaviour if you swap the cap. It's most likely a design flaw of the circuit itself.
