Are Your Capacitors Installed Backwards? Build this and find out 

In my 79 years of attending classes, primary, military, and advanced education, I've never had an instructor who presented as well as yourself. Thank you for sharing you time and knowledge.

Holy crap, your lab is like a submarine sonar room. I love it.

Wow! I never thought about how the physical construction of a cap would interact with nearby fields. 40 years in electronics engineering and I learned something new from this video! Thank you Mr. Carlson.

I must say, I took electronics in 1980. We started with tube theory and then semiconductors, and your knowledge is light years ahead of any instructors i ever had!!! I'm almost 60 now, and am still learning stuff from you! keep it up!

This is mindblowingly professional. I'm nowhere near doing any of this but I really appreciate the way it's presented and the thoroughness of your videos! Your work is impeccable!

Hi Mr. Carlson! The U.S. Navy trained me almost fifty years ago (avionics). During that time, and with all of the contact that I have had with engineers and technicians since, nobody else ever pointed out potential polarity issues with non-electrolytic caps!! I stumbled across this video quite by accident, but am so happy (and grateful) that I did! In retirement, the only electronics that I deal with are electric guitars and amplifiers, but you just switched on a bright light...shining on some of the 'mystery noise' issues so common with amplified guitars and basses! Thanks!! As a considerably less 'elegant' alternative to your new bit of test gear, I simply used a DPDT switch, a metal box (shielding, of course), some clear labeling, and physically switch back and forth between 'Normal' to 'Reverse!' I could have added LEDs, a couple of resistors, a battery, and changed to a 4PDT switch, but figured that the O-scope display was plenty! Works fine, was way less expensive, has fewer potential points of failure (like none!), and only took twenty minutes to build! I decided that, at 65, the 'KISS' principle would serve me better! :-) Thanks again....brilliant video!

Holy Cow!! 52 years as an electrical/systems/test/hobbyist engineer (analog and digital) with a BSEE and MSCS and I NEVER KNEW THIS. An outstanding explanation that explains why a troublesome noise issue is occasionally fixed by simply replacing what appears to be a perfectly good capacitor. If the band marking is only randomly the outer layer (and it's obvious in retrospect that it happens because the marking is being done last on caps that are dumped onto various conveyor belts during manufacturing - Duh!!) I'm astounded that sensitive circuits work as well as they do. I doubt that one engineer in a hundred knows this. Thanks for the great explanation, great design process and an outstanding little test tool.

Wow, has it been 9 years already? I remember when this video came out and eventually developed into an amazing final project with LED amplitude readout. Since supporting Mr Carlson's Lab on Patreon for all these years, I built this tester years ago and it's tested all of my capacitors for RF and Audio circuits and it's more than proven its weight in gold!! No more hum in my speakers!

I was viewing your video for the second time, and continue to amazed how valuable this video is to so many people. I have enjoyed their comments about what they did in their jobs, and what they have learned.

I have to thank RU-vid auto play for bringing my attention to your channel. As you opened the subject I had a slightly skeptical hat on, but as you continued I began to wonder if there was anything else so basic I had ignored for years? Brilliant video -outstanding,

I love to hear these old tube radios work as they did when they were new. I am always looking for them to rebuild and play again. I have spent hours watching these very informative lessons you produce. Patrion, yes ! Thank you for your help Sir.

I find it hard to understand why over 150 people could have marked this video with a thumbs down. I for one found this educational and important. thank you for sharing.

I had no idea this was even an issue. After watching this video, it makes perfect sense. Thanks for education!

Thanks for this great video. I'm retired from 50 years in the service industry. Always installed these caps with the band considered the outside foil. Wish I knew this years ago.

Thank you Mr. Carlson. Using your jig is so much easier than testing the thousands of caps I've done over the years by hooking each up to the Hantek. This is a great service to the electronics community!

Impressive and very informative video. As a seasoned electronics designer, this subject never occurred to me when using foil type caps in hi-Z circuits. Congratulations on yet another great video. Thanks and keep up the good work.

I have seen this before, but for some reason I was able to concentrate more this time. I always remember the instrument you created for sensing dysfunctional components or parts of a live circuit. You make electronics so pleasant to learn/refresh, even to previous electronic engineers who have spent many years off the bench, like me ! Thanks :)

HEY! The PCB layout, component map, and schematic are now available on my Patreon page. All the information you need to build your very own. Check out the community section to see other Patrons versions as well. Here is the link: www.patreon.com/MrCarlsonsLab P.S. if you like my videos, there are more on Patreon as well.

Great video! More than 35 years in electronics and I did not know this. Cheers.

In the beginning, when I was a teenager, I used the phono-ceramic input of my amplifier and watched the volume of the snorer in the speakers ... and it worked well! Greetings from Brazil, South America.

Learn something new everyday. I had thought that the line still meant the same thing as in the old days, Another great Vid, Dave W4GSM

It's one of the "top secrets of making a noise free tube amplifier". People sometimes doesn't belive when I do some maintenance on their amplifiers and they get it without any noise, humming, etc hahaha.

My dad worked at Western Electric and Bell Labs, retired in '69. He taught me about the foil. This is a great refresher, and shows the reason it is important. Nice job.

this is awesome. easily one of the best electronics tutorials i have ever seen on youtube.

Over 40 years in electronics and I didn't realise that the markings were useless. There you go... always something to be learned. Love your material !!

This makes a huge difference in sound on my soundsystem. Thank you for the explanation.

Hello there Mr Carlson. I hope you read this comment. I've been a Subscriber for a few years and want to let you know how much I appreciate all you do. You are up there with the best on RU-vid in my opinion and I wish you many more years of increasing success. Thank you for your expert presentations and commitment to excellence. Just wanted you to know..

I been in TV repair business for 35 years and I really enjoy how brilliant you are. I think the foil identifying device you engineered is great. I need to build one but for now I have to use a scope and a signal source. I restored a McIntosh 275 tube amplifier and all of the dy film capacitors we're oriented correctly but I was surprised to find that on eight of the capacitors the band was not marked on the shield and six were. I also found out I didn't have to replace them because they were not the unreliable paper types. One of the electrolytic blew its black tar out and made a mess so it got all new electrolytics. One of the 6550 did not have any emissions. It got all new caps anyway and I tested for foil side and made sure it went to the low impedance side. Now the amp plays beautiful but I was really surprised about the band. I even tested a wax paper I had laying around and it was even written FOIL SIDE with the band and it still was wrong. I wish I could send you those

Once again, an excellent vid and presentation. One valuable bit of test gear and very many thanks for sharing this... 10/10

This seems so obvious. I never knew of or thought about this. Blew my mind. Awesome video

Decades ago I learned all these stuff, even the technology of tube amps. You are absolutely right! Thank's alot for your explanations

Thank you for posting this I am a newbie to tube radio restoration and grateful for any tips I can get. It seems from the comments I have got on this one from the start when the old hands didn't know about it. Best regards Ron H Lancashire UK.

Great video. I could listen to you all day. Thanks for sharing your knowledge.

Thank you! This was super useful to me, both in educating me of the need to have the capacitors the right way around and in inspiring me to think and create test jigs. Thanks for sharing!

Amazing amount of information in

As a 'semi retired' EE, I really enjoy your videos. You are the kind of guy I'd like to sit down with and enjoy a few craft beers and talk nerd junque. Thanks and Regards

WOW... never heard about this before. Learned this new information from here today. Thank you very much. I really need to buy an oscilloscope..!

THANK YOU for all these amazing videos! Hopefully the few negative folks on here don't discourage you from continuing doing these. What you're doing is awesome, inspiring, and re-igniting my love of electronics and the love that others have too. PLEASE keep up the good work. ! I just loved the Thordarson T20W40 amp video!

Yet another reason this is by far the best channel on RU-vid.

I preached on this subject of outside foil for decades and was called a heretic. "Outside foil to ground" Thank you for this good video! 👍

Great stuff, explained well. I've been looking for this information for years.

I don't know anything about circuitry but i'm learning so much from watching your videos, this is amazing

Where was Mr. Carlson when I was in college. To be so young, and have so much knowledge, and able to explain everything in a way that anyone can capture his meanings. As an Engineer (retired NASA), watching his video's are not only informative, but enjoyable. I'm 74 years old, and when first starting my career, everything was tube technology. I had to learn with the changing of times as we moved into germanium, to silicon, and some SMT (luckily, I retired before it got to heavy). The transition wasn't easy for me, the professor's I had moved at a very fast pace, and you either got it, or with help from other students in the class, did the best you could. The actual knowledge came from the field where you used what little you had learned, and hands on taught you. I hope Mr. Carlson stays on line, I really enjoy the video's and his skills.

What an informative video. Like some others I was unaware of the polarity issue, I always thought only Electro caps were polarised. Thank you so much. Cheers from Down Under

Cool circuit! I worked at Westinghouse, Kodak and a leading university and did a lot of r&d and had to build a lot of simple test circuits and test beds like this! I’m going to build it but just use a dpdt switch to swap polarity and watch the scope! Let the toggle point to the grounded lead. I always thought the caps were marked correctly!!! Thanks for the heads up!

VERY helpful and VERY educational . . . thanks!

Excellent info and video. 30+ year tech and always noticed the band but never realized the significance. Thank you...Learned something new to file in synaptic storage :-)

Your Channel is amazing. I am a electronic hobbyist since mid eighties and radio amateur. But thanks to your channel I'm in progress to get even better in doing my work. Big thumbs up. Thank You for sharing your knowledge!

Hi. I'm really impressed that you were using a vintage Tektronix 547 "for real", and that it's not just for display. And your video was really helpful. Even though I'm quite experienced with capacitors, noise, hum and impedance, it was very interesting to "see" the differences of the polarity. I'm experimenting a lot with coupling caps, but I have never had the polarity (of non-polarized caps) in my mind. Happy to see your next videos. Kind regards, Max (Austria)

Clever Paul! I like it. I have a little rig using a DPDT switch in an Altoids tin that I use for this -it works and ends the unwanted capacitor juggling. Low part count, no IC's to zap. Sans LEDs -the switch lever points to the Lo-Z lead (foil out lead) . Circuit and concept is basically same as yours, just more caveman.

I Love your detailed almost scientific explanations !!! Keep up the good work !!

What everybody else said!! I also built CNY02253's double-pole, double-throw passive version but without the Altoid's tin! Your solution is useful, professional, AND a great project. Thank You!

Yet another obvious thing I didn't appreciate, never knew about, never read anywhere and was never told. I've been building circuits for around 40 years now and I'm now wondering what circuits I can/could go back to and tweak. This could even have been the source of oscillation in some circuits where I'd swapped out a capacitor to cure and now I see I could possibly have left the value the same but reversed the component!! Ya live and learn, what other obvious stuff don't I know??!! Jeez - Thanks for the insight, Cheers Mr Carlson from the UK :o)

Outstanding explanation. Learned something new and extremely useful. I'd like to try a 556 configured as a D-type flip-flop (manually push button triggered instead) along with the CD74HC4066 since I'm using through-hole PDIP components to reduce the parts count and circuit footprint. What a great project, thank you! You've gained a new subscriber :), cheers!

Thank you Mr Carlson for this golden nugget! This draws parallel to the 'pseudo balanced trick' played in recording studios to reduce hum by cutting shield on the input side of balanced audio cables

Mr. Carlson, I've been a EE for 30 years and never thought about what you covered in this video. Excellent coverage, will start paying orientation attention during all future amp builds. Thanks for the excellent tip. Craig

Awesome information & presentation. I knew the importance of electrolytic polarity. I never knew in my 40 years of electronics since the USAF of this and now appreciate learning of the difference in non electrolytic capacitors circuit orientation. You would logically think a capacitor manufacturer would understand this and come up with a standard and manufacturing process to identify the band end. It seems they may not know what you do and that would not be too surprising. You are a special person!

Great channel. Learning lots. As a guitar tube amp guy, I wondered what other people are doing to test for polarity of supposedly non-polarized caps and found Acid Fuzz Pedal's channel's video on their capacitor polarity checker. Using just a fuzz pedal and a guitar amplifier, he just touched the capacitor leads to the signal tipe and ground sleeve of the the instrument cable and you can clearly hear that one direction is much quieter than the other direction. This seems to be the same noise test as Mr. Carlson is addressing, but I'm wondering if it's as reliable/good as Mr. Carlson's tester. (I see some discussion in the comments about why a simpler tester using a switch might not be reliable, but I didn't follow. I'll have to watch this video again and read through the comments.). Really like this channel.

Thanks so much for your terrific work and great explanation of the operation of all the components. As a self taught electronics fan, your videos are a true treasure chest of information....now back to my world domination machine...

All I can say is "WOW" ........I'm going to try to build one of these and it makes perfect sense to me the way you have explained and demonstrated it. Thank you again.

Thank you very much for the video, I noticed that something was happening on one of the channels of my Headphone vacuum tube amp because I had hum from somewhere, then I did the inverting of the cap that goes to the plate and not any more problems.

Why didn’t I know this? I learned something today 👍

Your channel became my favourite one. Subscribed and supported via Patreon. After 16 years of "experience" I have a feeling that from now I can learn some really useful stuffs from you. You are Legend Sir. Thank you.

I've been doing stuff with solder and wires for over 50 years, I never ever considered this. I tried it and you are right....it works and I cannot be sure yet, but you may have solved a hum problem I've been having. Thank you very much.

So, a particular equipment model may have different signal to noise figures depending on what day / who assembled it etc. Very interesting indeed. Thank you. (P.S. I would pay just to sit in that lab!).

So, do you ever take apprentices? I can sweep a mean floor and make great coffee. :) I watch everything you do very closely and learn a lot. I feel fortunate that, as a newbie, I'm learning things at the same time as old timers are. Doesn't get better than that. Thank you.

Great info, well explained, and the production quality is top notch. Thank you for what you do! Would love to see more on the diagnostic process. I'm looking for the ones you already have, I'm sure there are several at least..

this is the ultimate bit of knowledge, and it makes the audio circuit work 100% with all hum gone

"Thank You", thank you very much😎 May I have a link to your capacitor test circuit🤔 Let me know, I look forward to hearing from you

This is Mr electric, he can be believed , plain and simple.

Sweet! Once again, a great education. One thing I wanted to mention, is that I have a lot of foil tape which is about 3 inches in diameter. I have used it for shielding on other projects. This is nice if you have plastic project boxes, and since the tape can be used to "Noise Seal" the inside of the box, you should never have a problem. Never tried to solder to it though... But for shielding from outside influence, might work a treat for something like this.

I'm convinced that with each passing video Mr Carlson is actually getting younger

I have known for years why we need to know which capacitor lead goes to the outside foil, but I am shocked to learn that we cannot trust the factory marking!

For people without a scope, one could also use a very simple circuit that uses a small but sensitive audio amplifier with a diode on the O/P connected to an analogue meter. This should clearly show which way round the capacitor needs to be by how large or small deflection is. It might even be possible to replace the meter and diode with a loudspeaker and hear the difference. Even a domestic or HiFi amplifier that has as mag input at about 2/3mV should work well as the input is sensitive and has RIAA EQ (ie bass boost) Be careful with levels, you don't wont to damage your loudspeakers!! or just buy a scope!! and make Mr C's tester.

You're a real genius! I'm learning so many things looking to your video lessons. that's what a teacher has to be... thank you! 🤗 🤗

This is fantastic! A concept I wasn't aware of, and a gadget build that I would find useful. Sweet!

Wow, you sound like my dear departed Dad, he was an electronics guy, I'm a metal worker like his Dad. I use very old Miller tig welders that use two .002 uf mica capacitors in parallel in the H.F. spark gap oscillator circuit. These welders last longer than some humans, but those caps don't! tar leaks out of them. I was given a box of modern alternatives to use, so far two types from Sangamo have worked well. Another wound or layered type he said would work but they are not marked for polarity. I wounder if it will matter, now that I've watched your vid. My guess is it would work either way, but send out H.F. interference more if wired in backwards. Can you advise and educate me further in this application? Thanks. Very neat vid by the way, reminds me of Dad, and I'm 59 so that's back aways.

I like this technique, I finally tried it out in replacing some paper capacitors with film capacitors in an old GR megohmmeter. But I find it easier to get a clear indication of which way is best with a good analog ac voltmeter with a 1 mV range.

If only i had a neighbour like you Paul. Its awakening my hobby of diy electronics

thanx sir. what a great video. for years I thought these caps dont have polarity or any particular direction and I was wondering why and its very obvious now . very recently I worked on an amplifier circuit and it was picking up some noise regardless of all the efforts to pin point the problem and after watching this video I made those corrections and it became absolutely quite. wonderful!

You are very gifted sir, and I always learn from your videos, but I must ask, why not just use a simple dpdt switch.

Can you upload a document with the diagram and the parts you used? It's hard to figure out from the video. (5 mV is the minimum accuracy)

Very nice test box to determine correct polarity of the capacitor so they can be installed correctly. Another successful demonstration and thanks.

Great video, pleasant, concise, and complete! Always a pleasure learning from you.

I mean, your talking about the issue of interference sheilding, but it is not a polarity issue like in DC electronics, therefore marking the line on the one side is not to be confused with the line that would be on one side of an electrolytic capacitor.

at 73 i always thought the line denoted outside foil.you showed i was wrong. i'm not building anything as i am satisfied with the earlier experiment showing the where the outside foil is by introducing a signal with your body. i hope my electrolytics are correctly marked :>) barry

Hello, i just subscribed. Thank you for doing this. I'm 30 and didn't had a chance to get such education so i'm learning now. It really means a lot that i have a chance to learn from yout videos. Kind regards from Slovenia.

I've been binge watching your videos for three days now. I think my brain is bigger already. I also start my Masters Degree in electrical and electronic engineering later this year!

is there a tester you can use that does not require a scope for checking these ?

Mr. Carlson you should make and sell your creations I believe you could be very wealthy No body makes equipment with the quality that you design. I would buy one of those. BK Precision move over. Carlson Designed Electronics I like the sound of that...

A fascinating demonstration of questionable capacitors; especially dealing with RF fields that can be a real nightmare to service. This is an excellent video for demonstrating such issues.

Great video. I am an retired Electronic Engineer, working at General Time on quartz watches, then currency counters and finally prescription pill counters. This was a great video. Thanks again for doing this.

I have a cheap 2 channel, 100mhz digital rigol scope (DS1102E I think it is) and even using a coax cable I can't reproduce the high/low noise effect by touching the cap. I have it set to 5mv per division. I'm not sure what I'm doing wrong. Anyone have any suggestions? The caps I'm testing are 650V orange dips, if that matters.

Hi vicegrip33, You have all your youtube settings on private, so there is no way I can respond to you. Your reply tab will not allow a response as well. You need to edit your youtube and G+ settings. I don't think the capacitor orientation would matter much. What would work for you is... Two large capacitors out of a broadcasting application. They can deal with High RF current. They look like these www.mwpersons.com/Used-Capacitors.html

Hard to believe there are 'thumbs down' (dislikes) for your videos. You speak clearly and precisely. take your time explaining what you are demonstrating - and are knowledgeable. So what's with the thumbs down(s) ???

I was repairing an audiocompressor kit build few months ago and when going through a calibration step all of a sudden this oscillation appeared when a pot was set halfway it was inaudible but I could see it on the scope then I recalled this video and voila! Flipping the orientation of a foil cap sorted it, thank you

Mr Carlson, would you mind releasing the PCB layout?

60 years in electronics and I never knew that.

Amazing device created. I appreciate the thoroughness. Thank you.

Well, DAUW! Who would ever have thunk this? Obviously Mr Carlson.... I started studying electronics 57 yrs ago, specialising in digital (ones/zeros/edges) and have also been a HAM for 40+ yrs. I don't think this has ever bit my butt, but who knows? 'Mr Carlson' will pop onto my mind every time I deal with capacitance, real or imaginary, again! Thank you Sir for this very instructive vid..... 73 OM