Using an ESR Meter to Determine the 'Health' of Electrolytic Capacitors in Guitar Amplifiers

[@timothyb1559]

Watching Uncle Doug videos after work is like going to night school. Thanks, Uncle Doug for your library of outstanding informative videos.

[@UncleDoug]

You're quite welcome, Tim. Glad you enjoy them.

[@UncleDoug]

Thanks, Gellmann.....stay tuned for a follow-up video (or two). ESR measurement is a rather novel, interesting field of study with regard to guitar amplifiers, and I hope to come up with a lot more useful information.

[@UncleDoug]

Great news, Dave. I'm glad you acquired this wonderful new "toy". Isn't it interesting how our tastes change with age? From cap guns and bikes......to ESR meters. I found that with a little use and experience, you can make rapid, accurate assessments of electrolytic capacitor "health", and it's actually fun to do. Thanks for the great comment and best of luck with your electronic repairs.

[@johngeddes7894]

I, for one, don’t give a damn.

[@UncleDoug]

Thank you.....I agree that the subject is open to discussion. In a properly fused and grounded amp, I don't really see fire or electrocution as likely occurrences, but I would agree that in an amp used by a professional musician, where reliability is essential, fresh filter capacitors would make good sense....and if the existing electrolytics are causing noise, then they should be changed. But if the original electrolytic capacitors are functioning well, as they are in about 90% of all the.....

[@ElPasoTubeAmps]

This is a wonderful investigation and demonstration of how to first determine if a capacitor is bad before wholesale replacing all of them and often times destroying the vintage quality of this great old equipment. Thanks for the research and posting.

[@davewilson6324]

Uncle Doug... I got my ESR meter in the mail yesterday through Amazon.com. I open my new meter like a little kid on Christmas. What a treat.... this thing works great and it's very easy to use. Thank you for introducing me to this great insterment!! I really enjoy your video!!

[@lupojacobo9892]

Same here

[@UncleDoug]

amps I have encountered and owned, then I see absolutely no benefit in replacing them. This is not so much a slavish devotion to originality as it is simple common sense. The ESR meter allows us to detect hidden but impending failure in electrolytics, and thus is a valuable tool for determining which capacitors should be preserved and which should be replaced. I hope to gain a lot of additional experience and knowledge from this device and will report what I find. Thanks again......

[@UncleDoug]

Thanks, David. I was pleasantly surprised that the ESR meter reaffirmed our conviction that older electrolytics do not necessarily require replacement. More investigation is definitely indicated in this area, and further studies will be posted.

[@jorgeandrade20]

This video is now almost 10 years old, are there better meters in existence today? Could you recommend one?

[@UncleDoug]

@@jorgeandrade20 I still prefer the same Anatek Blue ESR meter featured in the video.

[@georgechambless2719]

Excellent! I've restored a few antique radios over the years and always wondered if the old capacitors were worth keeping. I have a huge box of them and am looking forward to testing them with an ESR meter. Thanks so much for these videos...I just subscribed to your channel.

[@UncleDoug]

George Chambless You're welcome, George, and thanks for subscribing. Let me know what you discover when you test the old caps. Granted, the ESR value is only one of three tests, but I think you'll be surprised by how well a bunch of the discarded caps still function.

[@nathanpratt3058]

I really like how u try to keep things original, I have always been that way and appreciate that your the same way

[@UncleDoug]

Thanks, Nathan.

[@UncleDoug]

Google +, your comment came without a reply capability so I'll answer up here. How many parallel or series electrolytic capacitors do you routinely encounter in circuits? In vintage amps, they are quite rare, since the circuit designers simply specify a single cap of the correct capacitance and voltage rating. The exception is in Fender Bassman-style circuits, where two 70uf @ 350V are used in series to achieve 35uf @ 700V.....not easily found in a single cap. Even then, the ESR meter will read the pair as if they were a single cap, and if either is truly out of range, the average reading will reflect it. You can theorize all sorts of pitfalls, but the simple truth is, in practical day-to-day usage, the ESR meter can be reliably used on circuits with all connections intact.

[@jakewells9403]

Doug i am not as lucky as you most of what i work on is tube radios and 75 % of the time i run into either shorted or open electrolytics though sometimes i get a set that works really well but has a considerable amount of hum. I went through a philco from the 30's with aerovox caps that looked to come out of the 50's the set worked ok but had considerable hum they where both 8 mfd units at 450 volts both had leakage at 100-150 volts with a power factor ( ESR ) of 15 - 25 my personally tester is a Eico 950 B thanks for the video. - Jake.

[@TheGuitologist]

This is extremely helpful. I need that meter.

[@UncleDoug]

Greetings, Brad. As others have said, since the ESR meter does not test electrolytics at full voltage, it does not provide a complete evaluation of their status, but it does provide valuable information without the need to remove the cap from the circuit. It is quite rare to find a capacitor that tests well on the ESR meter that is not "healthy" and usable.....and it allows you to quickly weed out those which are not.

[@rsattahip]

Cheaper and better to just replace all the wax, tubular or can capacitors in the amp if it's old. Those parts cost less than 50 cents each and modern replacements for the electrolytic can type are only a few dollars and there are not that many in the amp. Be sure to get the polarity right. Why buy a meter you're only going to use once when buying a few capacitors is costs much less. If the large filter (can type) capacitor is bad or failing you'll hear a hum in the speaker.

[@stephenchow5161]

you retain more value of vintage amps with the retention of original parts that dont need to be changed which can add up to hundreds of dollars

[@rsattahip]

Stephen Chow I never knew that. I knew visible modifications would lower the value of antiques as they do with cars, but not replacement parts. Thanks Tube electronics have a certain beauty to them the new stuff can't match.

[@UncleDoug]

Thanks, JZ. I really appreciate your input and support. Good day to you too.

[@carloschafin1]

Doug, this is really eye opening. I have been taught to replace old electrolytics since I began repairing guitar amps. The shop and guys I worked with, it was a just a given to replace them, same with the old paper wax ones. I've wanted to pick up an ESR meter for a long while and this closed the deal. Thanks again for another great tip.

[@UncleDoug]

I think you will be surprised just how long-lived and resilient electrolytic capacitors can be, Carlos, especially those which are very well sealed within their enclosure.

[@abubakr6939]

I opened up a 1961 fender bandmaster head, lifted the metal hood on the electrolytics, looked like new, worked great also!

[@UncleDoug]

Greetings.....I looked up the MESR unit, found a couple reviews of it, and can find no fault with it. I can't vouch for a device I have never personally seen or used, but it would probably serve the intended purpose. If you get one, please let us know how well it functions. Thanks for your nice comments.

[@Blaydrnnnr]

I posted on the video for " The worst capacitors I've ever seen and heard" and was asking you about measuring the electrolytics in circuit. Extremely helpful Doug. I ordered this meter, along with the Signstek MESR V2 as well. This was exactly the info I was looking for. Great stuff, learning alot. I'm just beginning to work on my vintage amps, ( Marshall, Hiwatts, Sound City, Fender ) and was looking for ways to measure the electrolytics in circuit to determine if a cap needs replacing or not, without de-soldering. My first project is my '85 JCM 800. Re-biasing new power tubes, changing all filters, but wondering about the others, if they NEED replacing, so testing to some degree of certainty would be cool. Thanks!!!

[@UncleDoug]

You're welcome, BR. I'm glad the video was helpful. Best of luck with your repair projects.

[@lavejim11]

Thank you for the great vids.. I just recently found your channel, and I admit I have been binge watching. Have watched all your posted videos in the past week. Your explanations are great, and I've learned a great deal. Now I want to go out and build an amp!!

[@UncleDoug]

Jim Lavespere You're welcome, Jim. Rusty and I welcome you to our channel and sincerely appreciate your kind words. By all means, start planning your first amp-building project.....it's a great hobby :)

[@j.dragon651]

I was lucky enough for one of the EEs at my last job give me the same tester. Now I know how to use it thanks to you.

[@UncleDoug]

What a nice gift, Jerome. Good luck with it.

[@j.dragon651]

@@UncleDoug my only problem is I just moved and it is packed somewhere and I haven't found it. I found everything else.

[@UncleDoug]

@@j.dragon651 Good luck with your unpacking :)

[@ncilmo]

I have been using my Blue ESR since I purchased it this summer. I love it. Thanks for doing this and all of the videos that you produce. They are much appreciated.

[@UncleDoug]

You're welcome, Dr. Kemp. I'm glad You're pleased with the Blue ESR meter. Thanks for your input :)

[@djfrank59]

I've purchased one of these puppies recently, and basically found it to be a useful troubleshooting tool! However, if I do find a cap that gives me a borderline reading (suspicious), I use my old EICO capacitor checker to back it up and test the cap at it's rated working voltage. I've found many paper caps show leakage at only 25 volts of the 450 volt rating of the cap...no sense bringing the voltage up too much higher. For the most part, I trust the ESR meter to a very good extent (a lot more than a digital cap checker) I find the ESR meter excellent with the lower voltage caps used in solid state circuits! It's been on target! The Blue is definitely worth the money and a good investment for any tech shop...Hope this input helps :)

[@UncleDoug]

Thanks for the input, Frank. I've never really seen the benefit of removing an electrolytic from a circuit just to test it at full voltage.....and then, I assume, re-install it if it passes. Once it's out, you might as well just replace it. My way of testing electrolytics at full operating voltage is simply to plug the amp into a current limiter and turn it on. Shorts, leakage, etc. become readily apparent without risk to the power transformer or other components. It's a quick, easy, and accurate. Afterwards, I discharge the caps and test them with the ESR meter to see if their capacitance is correct, i.e. beginning to fail, but not yet producing an audible hum.

[@skeeterbuck1355]

Thanks again Uncle Doug for the "shared knowledge" on the tone caps and pet you faithful "camera man" Rusty for me.

[@UncleDoug]

skeeterbuck You're welcome, SB....and Rusty says "Thanks for the ear scratching" :)

[@psalys]

Hi Uncle Doug. I couldn't find an assembled Blue ESR meter so I bought the kit. I figured, how much assembly could there be for $20 difference? Ha!! Turns out, a lot. It took me about 6 hours but it was a fun and rewarding project and it works just like in the video. Thanks for the recommendation.

[@UncleDoug]

I figured the $20 extra for assembly (on mine) was money well spent, Patrick. I'm glad your construction went well and that the unit now functions well.

[@jayingram5724]

UNCLE DOUG!!! you have always got the slickest old tube amps EVER!!! you are a WIZ at sniffing out those old gems! i would love to go flea mktng or yard sale shopping with you, sir!!! LOVE ALL YOU COOL VIDS!!

[@UncleDoug]

Thanks so much for your nice comments, Jay. To be honest, the pickin's have been pretty slim lately, both for vintage guitars and amps. Hopefully, things will improve for both of us.

[@UncleDoug]

Recent case in point: A local pawn shop is offering a used Epiphone 100th Anniversary "Les Paul" guitar for $1195......which seems a bit pricey when you consider that they sell for around $750 new in case with paperwork. Even when they do get a decent guitar or amp (which is rare), the pricing is absurdly high, making the purchase impossible.

[@jayingram5724]

good lord... that is why i just buld my own guitars... and at the rate im aging... they just about start out as antiques!!!!! and thanks to you and your online tube amp courses... im just about not in need of store bought amps either!!!

[@jflimbach]

Uncle Doug: Nice amp. I've learned a lot from watching your videos that has helped me restoring old amps. My restorations are made to play and I'm not too much concerned with keeping it cosmetically original but functional. I am of a somewhat different opinion on electrolytics, particularly in the power supply. So, to me a 40+ year old electrolytic that hasn't failed yet is a ticking time bomb. It's gonna go eventually and maybe take something else with it so I routinely replace them first thing. Also, when it does fail, it means another disassembly to fix. This isn't so bad on an old Traynor where you just pull the top off, but I'm working on a 1993 Feder Concert at the moment which is a nightmare to get into and I sometimes consider just scrapping for the parts rather than go through the agony of putting it back together. I also replace paper caps routinely especially in old radios since I haven't found any that were 40+ years old that weren't leaky. If they're the rare, high quality tone caps and I'm going to try to keep them, I first do a leakage check at the rated voltage. If they pass, they can stay otherwise I replace them with new Jupiter or Astron caps. Never had a problem with ceramic or micas, so don't bother with them unless they're causing some kind of disruption in the circuit. Different strokes, etc. Love your videos and eagerly await the next one.

[@UncleDoug]

+jflimbach I agree with virtually all that you say, JF. I replace all elderly electrolytics that cannot pass ESR testing, even if they are marginal. Those that pass with flying colors are allowed to remain. Over many years with many, many amps, I have not experienced any problems with this approach.....however, I agree that there is some risk involved. To be honest, though, I have encountered more problems with new, modern replacement capacitors (which are of varying quality) than with (generally high grade) vintage caps which pass ESR testing. There is no "100% sure" option.

[@alkoenig85]

Oh boy! Another meter! Interesting presentation, a new tool, and a reason to keep my hands off of those caps. 100%!

[@UncleDoug]

Thanks, Al :)

[@SuperJetjockey]

My combination ESR tester arrived last week, and I am absoutely thrilled with it. In the meantime, my beautiful Hickok 1600B VTVM has failed and I can't find a schematic anywhere. I have checked the tubes with a transconductance tester, and suspect that it is yet another failure of an electrolytic cap. I am going to attempt an in-ciruit test of the caps first, to see how well this is going to work for me. The unit is super clean, and there is no obvious sign of any failed components, but you know it is never easy. Thanks

[@UncleDoug]

I'm glad that you're pleased with the ESR meter, SJ. It should prove useful for your in-circuit testing of the capacitors in your Hickok VTVM. Best of luck.

[@johncunningham5435]

I agree with you Doug that it is unnecessary to recap the whole unit; like you, I prefer to keep the vintage appeal. The fact is that very few fail that need attention. I also use an ESR meter to determine what needs to be done; however in some cases the cap must be pulled and tested at rated voltage to check actual operating conditions because some will break down near their rated voltage. "Great Video"

[@UncleDoug]

Thanks, John :)

[@UncleDoug]

Yes, it was my impression that the similarities to the original were purely cosmetic and that the circuit was much simpler and less expensive to produce. I believe the "reissue" sells for only $200 or so. What you describe makes good sense, since this would be about the cheapest possible tube amp circuit to produce. An enterprising individual could probably alter the simplistic "reissue" chassis to more closely resemble the original.

[@tonyd1149]

Dear Uncle Doug, thank you for making and posting this video. Your manner and teaching ability is excellent. (I love your ESR meter). Thank you again. God Bless. td\.

[@UncleDoug]

You are very welcome, Tony :) Thanks !!!

[@johngeddes7894]

Uncle Doug-More points of interest. Always a good thing.

[@UncleDoug]

Thanks, John :)

[@IceDragon67]

Thanks for all of your awesome videos Uncle Doug! They are really informative and helpful!

[@UncleDoug]

You're welcome ID. I'm glad the videos are helpful :)

[@ferndog1461]

Thank you for walking me thru the electronic mindset. SENSEI, please consider Amazon links so your fans can help your channel. Your channel is the Vocational school for the millennials. Thank you so much!

[@UncleDoug]

You're welcome, F. I am not familiar with Amazon links, but do include PayPal and Patreon links in the video description.

[@mikeduino4596]

One option to purchasing an esr meter for 100 bucks is to build your own, as I chose to do. There are a number of plans online and if you have stuff lying around as I did it will only cost a few bucks. I used a 555 for the 100khz oscillator. Also, If you measure a cap with an ohm meter, and get a reading there is a serious problem with the cap, as caps appear to a DC current as nothing more than an open set of contacts.

[@UncleDoug]

I never thought of scratch building one, Mike, but it sounds like a great idea. Since I deal only with vintage tube amps, I just don't have any "modern" components :) Yes, you're definitely right about capacitors appearing as infinite resistance to DC ohmmeters. One of my tests for capacitors is to verify this. If any of them have a measurable resistance, I assume they have an internal short.

[@photoexpert3771]

Thanks Doug for a grrrreat Feature. You are spot on when you say keep original. I have a 1964 Leak Delta 70 amp and it sounds and functions perfectly. ALL the internal discreet components are original i.e made by Mullard and other components i.e capacitors are all British. Please can you make more of a similar nature. Cheers.

[@UncleDoug]

You're welcome, Brian, and thanks for your very nice comments. They are only original once.....and it's nice to keep them that way. A highly restored vintage amp is not much better than a re-issue :)

[@ZilogBob]

Hi again Doug. Your experience is the same as mine. Those old electrolytics were probably made by Mallory or Sprague or one of the other big US companies and they were made to last for decades. It would be surprising if any of them measured a high ESR value. The electrolytic caps which fail are the Asian ones in switching power supplies and CRT TVs, cooked to death by high ripple currents and being close to heat-generating components. Like they say, "If it ain't broke, don't fix it!".

[@UncleDoug]

Amen, Bob. It's great to hear a reasonable opinion, rather than the knee-jerk PC attitude of wholesale replacement of all vintage components.

[@mauanderuk]

I totally agree people get an old amp and just change all the caps, that is not fault finding and like you say they replace them with caps that don't perform as well. I think modern caps are much smaller but not necessarily better. Just stumbled across the channel its very good many thanks even though I am not into valves still finding them interesting.

[@UncleDoug]

Welcome to our channel and thanks for your input, M.

[@eeeeetfish]

Thanks for posting - I have mono (Quicksilver 8417s) and one is starting to distort - interestingly its fine initially but then degrades ,so something is amiss. My intention was to use my meter a fluke to compare the one working amp to its nonworking twin I think the problem may be as it works at first the bad part may be a bit hard to detect . Do you still have high regard for the AnaTec?

[@UncleDoug]

Yes, I still use the Anatek ESR meter often. With regard to your distortion problem, it's probably due to a resistor or capacitor that is malfunctioning due to heat and load. A good way to pinpoint it is to spray each resistor and capacitor in the circuit, one at a time, with a freezing spray......then listen to see if the distortion ceases.

[@larrydering1598]

As always, good information and accurate presentation. I enjoyed the video. Please continue with your topics.

[@phillipkobzeff2529]

Thankyou for taking your time and making all of your videos! Priceless. What did you do to gain all of this knowledge? You explain things so well that even I can understand the hows and whys of every topic I have watched. Can't wait to watch more. Thankyou again and I wish you the best. P.s. How's Jack?

[@UncleDoug]

You're welcome, Phillip. I was a school teacher for about 18 years. Over time, you develop effective ways to convey information. Jack is taking a nap now, resting up from all his deviltry this morning.

[@Galfonz]

one other test is a leakage tester. It tests resistance using a voltage similar to the circuit voltage.

[@UncleDoug]

I'm not sure if it tests resistance, Galfonz. It would probably be more useful to apply the DC operating voltage and then test to see how much, if any, can pass through the capacitor.

[@jeffjeff370]

and That is wy you dont need an esr meter! it is in only good use with low voltages

[@binarybox.binarybox]

@@jeffjeff370 Agreed. ESR meters are for low voltage checks to see how much AC current leakage there is at 100KHz. I have receivers to check and I will be using a Heathkit Model 3 and Model 11 which have a magic eye display. They are switchable on the test voltage so they can check up to 600 volts (on the 11, I think ) if necessary to see if and when a breakdown occurs. It's an eye opener to see a 400 volt cap start leaking at 25 volts.

[@skeeterbuck1355]

Hi Uncle Doug, Thanks for the heads up on the Anatek Blue ESR tester. I recently purchased the kit and it went together rather easily. Now I'm set for the checking the larger value capacitors. What method do you use for testing the small "tone" Capacitors like 0.01 and 0.047 etc.? Thanks!

[@UncleDoug]

skeeterbuck Greetings, SB. The Blue ESR meter is theoretically only intended for testing electrolytic capacitors, with values of 1uf or more.....but I have found that it yields very reproducible readings with non-electrolytic (non-polar) capacitors of .01uf and above. If you have a bunch of new, non-polar caps, test several of the same value and you will see that it yields consistent values for them. If you then encounter a capacitor of the same value within an amp circuit, it should yield this same value. I am still trying to determine if faulty caps in circuit will yield a different value and would thus be detectable with the ESR meter. I don't have enough data yet to make any definitive statements, but it's an interesting concept.Meanwhile, customary tests like measuring capacitance and DC leakage (mainly for coupling caps.....see Internet sources for leakage testing procedures) are routinely performed.

[@RonS387]

As a retired electronics tech that used to have a "Creative" brand ESR meter at work, I would tend to go with your ESR readings, and not the DMM capacitance readings. The DMM readings may be inaccurate due to the can capacitor still being 'in-circuit'. I see from the schematic that one terminal of the cap is tied to a second terminal on the cap with a 27K resistor, and this could affect the readings. (I realize this is an older video and there are over 300 comments, so this observation may have been mentioned previously!)

[@UncleDoug]

To me the DMM readings are simply one of several tests for capacitor "health", Ron. I also generally test electrolytics with the ESR meter and coupling caps for DC leakage with a voltmeter.

[@cgavin1]

I use an old Megga insulation tester I got on fleabay for £20. It will put 500v through a cap and show you how it charges and whether or not it leaks or returns to infinite resistance. Very useful tools for not much money. 👍

[@UncleDoug]

Thanks for sharing this tip, Wozzle :)

[@davidrourkemusic]

Hey Uncle Doug! I recently acquired a Gibson GA-50T from the 50s. You mentioned in this video that you used car wax on the control panel. Could you possibly upload a video, or point me in the right direction if you've already made a video on cleaning/rejuvenating old tube amps? Greetings from Canada.

[@UncleDoug]

Greetings, David. I have posted a whole bunch of videos showing how to refurbish old amps. One in particular would be the restoration of a blackface Princeton Reverb. Check my video list for it and many others like it.

[@davidrourkemusic]

Uncle Doug thanks uncle Doug! Much appreciated

[@UncleDoug]

You're welcome, David.

[@surgingcircuits6955]

Love the Blue ESR Meter. You can check batteries up to 50v with it, too. Note, however, if you check caps in circuit, you have to make sure the cap is not in parallel with other caps, or the reading is for all as a whole. You can have a bad cap and not find it.

[@UncleDoug]

Thanks for your input, SC.

[@surgingcircuits6955]

@@UncleDoug , revisited and I think instead of caps in parallel reading combined, it actually might give you the best cap and hide the worst ones! So, best to pull the caps or lift a lead on each to test. Cheers.

[@UncleDoug]

@@surgingcircuits6955 Since we are measuring the "series resistance" in parallel capacitors, the capacitance will add but the resistance will follow the parallel resistance formula, which means that for two identical resistors in parallel, the net parallel resistance is 1/2 the value of either resistor.

[@surgingcircuits6955]

@@UncleDoug kzbin.info/www/bejne/qqDUZKCpisqEapI

[@thomasgreenan8617]

I love this guy. Uncle Doug for President!

[@thomasgreenan8617]

And Rusty for Vice-President.

[@UncleDoug]

+Thomas Greenan Thanks so much for your "vote" of confidence, Thomas. Rusty and I stand ready to serve our country......as long as there are plenty of beer and steaks in the White House refrigerator :)

[@UncleDoug]

You're right, Carlos. Jacks travels are generally limited to his cat box, food dish, and favorite napping spot. He would be ideal for this cabinet post :)

[@raymondheath7668]

Yay! That's what my mystery transformer on this old amp chassis was, the speaker transformer!

[@UncleDoug]

If it has two wires connected to the speaker......or two wires that look like they once were connected to a speaker.......then yes, it's the output transformer.

[@SiliconSet]

A very helpful video Doug. Many thanks!

[@mechmusicman]

Uncle Doug, Thanks for all the great videos. I have one question about this video. When you measured the capacitance with your volt ohm meter "in circuit" were two of them essentially in parallel? Shouldn't they then read double as a normal reading? The third isolated through the transformer. RH

[@UncleDoug]

Greetings, RH. Yes, when you get a "double" capacitance reading with a regular (VOM) capacitance meter, it's almost always because the cap you are measuring is in parallel with another cap somewhere in the circuit. Sometimes, the parallel relationship is not evident (unless you have a schematic handy). Fortunately, with an ESR tester, surrounding components do not influence the reading.

[@bax737]

Uncle Doug, There is another factor to consider - if there are two or more parallel capacitors to measure, the ESR reading will not be accurate. If you measure the ESR across more than one parallel capacitor, and if one is high (bad) and the other(s) is/are low (good), the ESR will show a nice low series resistance. Only way to to it correctly is to remove the all but one of the parallel capacitors from the board and test separately. Thanks for the great video, and I hope I made sense.

[@curtismuma1931]

Hello U.D. i lov this video! And thank you for your past advice! Thank you. I have the same meter as you. But my only concern is, that the graf on the meter is so vague of the range of a good cap ,that i don't trust it. Also there nothing for high for high value uf caps. Do you have a spread sheet of the values, for different caps? Or any information where to find? Thank you so much! For being a master mind! Very impressed!

[@UncleDoug]

I agree, Curtis. Here is what I do: Whenever measuring used/vintage electrolytic caps, I first measure several new caps of the same capacitance and voltage rating, to get an idea of what is a proper ESR value. This method will also detect any faulty new caps that you might have. On circuits that have not been energized in many years, the ESR values may drift upward, but should not greatly exceed expected values. If you measure their values after energizing the circuit (and of course, discharging them manually) you will find that their values will drop significantly.....indicating to me that they have "reformed" due to use.

[@UncleDoug]

Also, you could record and tabulate your findings with new caps and prepare your own chart, if you wished, so you could forego the need to establish a norm prior to each circuit measurement.

[@curtismuma1931]

@@UncleDoug Great advice, i will Build my own chart. Thanks for the reply!

[@bailamosmundolatino]

hallo Mr Doug ESR70 is good. I prefer to disconnect cap and mesure it individually specially if they are in parallel twoor three like in a power supply. Equiv series resistence are in parallel too !!! That means that you will not probably see the bad capacitor in the circuit. Very good video. Best regards. BEN

[@UncleDoug]

Greetings, Ben. The Anatek Blue ESR Meter can accurately evaluate capacitors in circuit, whether in series or parallel, so you don't have to remove any leads prior to testing.

[@sixstringmarauder]

Hey uncle Doug, thanks a bunch for all you do, where do you find those schematic prints and do you or have you ever worked on any vintage pioneer stereo receivers.

[@UncleDoug]

You're welcome, David. I find and download all my schematics from the Internet. Also, you can check my Facebook page: Uncle Doug's Vintage Amps for a posting from a viewer who was creating a nice, legible library of schematics. No, I only work on vintage tube (guitar and PA) amplifiers.

[@CSSIandAssociate]

I found your website with the current limiter and then immediatly went to this one. I have been interested in this meter for some time. As of late my 50" Samsung Plasma screen went black. I think it is the T-Con Card, however since it was all the way in the back. I wanted to measure everything I could I have 3 DMM's and a 50MHZ Oscope yet not this ESR. I concure with you "if" you have this ESR you can be assured reasonably your equipment is in good shape. With that said do you have a maintence schedule on your amps? The Plasma I mentioned cost me $2,000 new. So, every so often I thought it would be good idea to go in and re-measure sort of like a check up. Your thoughts? Uncle Doug thank your for your fine work..... I added you to my subscribed list and will check often. I do not have an Amp however I do have Fender DG 10LE now I think I will build my own Amp. I you have any resources on this endeaver please share.

[@UncleDoug]

William Ward Greetings, William. The ESR meter is particularly useful to test electrolytic capacitors that are still in-circuit, i.e. attached to the circuit board. I don't do periodic maintenance on the amps, but I do use the Current Limiter every time I fire one up that has been dormant for a while, and I perform diagnostic procedures only when malfunctions arise. Thanks for subscribing and watching :)

[@victormartinez4540]

Hello Uncle Doug! One question... one terminal of the ers was conected to the can cap... the other one was Connected to the chassis (ground)? Thanks. Best.

[@UncleDoug]

I'm not sure I understand the question, Victor. Generally you attach one lead to the positive and one lead to the negative lead of an electrolytic cap.

[@Jmoog]

I was also confused by this. You can clearly see the one lead on the lug of the can cap but the other lead is showed connected to something out of the picture. What was the other lead connected to? Where would one find the "negative" lead of a can cap?

[@j.dragon651]

I found my tester in my pedal steel guitar case. Now I can watch the video again. I have it and some caps in my lap. I bet you have a cat in your lap. I am going to check a bunch of NOS, 50,s,60s,70s and some vintage used ones

[@UncleDoug]

Good luck with your tests, Jerome.

[@MiguelIFonseca]

Sometimes I test capacitors with a DMM to check if they've gone low resistance and they leak initially but then after a few seconds their resistence goes up to infinity. Are these really leaking or is it an effect of the DMM autoranging? If so, these cases might be the pathologic examples where the ESR meter beats any other test available.

[@JamesLewis]

I know your post is old, but perhaps someone else might benefit from this answer even if you've learned why.... The DMM's resistance check applies a small voltage to perform the test... the cap will show a low resistance until it charges to the test voltage.

[@irusman62]

good day UD on the electrodynamic speaker, does the electro magnet change polarity opposite to the speaker coil, or does it just stay the same polarity while the amp is on? or is the “dynamic" meaning it changes?

[@UncleDoug]

The field coil electromagnet retains its polarity while the voice coil polarity shifts with the signal.

[@Lenny8679205]

Will the ESR determine leakage in mica caps (mmf) in old tube radios?

[@UncleDoug]

Len S Probably not, Len. It's primary function is with electrolytic caps, generally 1uf and above.

[@Lenny8679205]

Uncle Doug Thanks, Doug and Rusty.

[@thermionic1234567]

I just changed the .1 coupling caps in my 6B4 amp as my ESR meter gave me grossly-different values. I think the lowest it goes down to is approximately 2 mfd. The problem I had was solved; but when I measured the caps I removed, they both tested the same. Could the bad one have recovered? I hadn’t used the amp for around two month...

[@UncleDoug]

I wonder if the fluctuating cap's in-circuit reading wasn't affected by a neighboring resistor.....possibly in parallel (?)

[@johnb5519]

Love your videos there Uncle Doug. Do you have to discharge all the caps before doing these checks?

[@UncleDoug]

Yes, I do. It's easier than waking up in the ER with a bad headache and an outrageous medical bill :)

[@mzeromusic]

Hi Uncle Doug & Rusty! First of all thanks so much for your video series... Your teaching very well fills a BIG gap in tube amp education, and I'm very grateful.... After watching your ESR meter video I went to the Anatek site to check out the Blue meter, and am planning to order one... Had a quick question: in the Anatek video they said you can't reliably test capacitors in circuit when they are connected to a power rail in parallel.... That you could have a bad capacitor that wouldn't read bad because of the other caps on the line.... Just wondering if you could pass let me know your thoughts... And one further question, would love to know your thoughts on testing non-polarized caps? I am in total agreement with you about changing parts in vintage amps... I perfer

[@UncleDoug]

You're welcome, SF, and thanks for your kind words. I only recently found out that Anatek had decided that the Blue meter was ineffective on electrolytic filter caps in parallel. Up until this point, I was under the impression that it was accurate with all caps in circuit. I have not yet performed any experiments to evaluate the situation, but intend to do so. Re non-polarized caps, I have found that the meter does give reproducible readings on caps down to .02uf. I made a capacitance vs ESR value graph using new capacitors ranging from .02uf to 1uf. Now, I can measure the capacitance of all the caps in this range, in circuit, by comparing their ESR value with my graph. It's my assumption that failed NP caps will give erroneous ESR readings, but am still gathering data to support or negate my assumption.

[@mzeromusic]

Uncle Doug Thats for the reply! I plan to order a meter in the next few days and I'll work on measuring NP caps... Once I get some data I'll post again.....

[@UncleDoug]

I performed the experiment we discussed above and will be posting a video of it very soon. I think you will find it interesting.

[@sharonlee4773]

Hi Doug,So you wouldnt replace the 2 caps that have too high a capacitance reading?

[@UncleDoug]

When dealing with customer amps, I now tend to replace all electrolytic caps, Sharon, just to avoid any problems in the future.

[@tremelo68]

Hi Doug. Any experience with the Atlas ESR70? Seems to do the same thing but with a few more features that could be helpful

[@UncleDoug]

I have not ever used the Atlas ESR meter, T68. Perhaps a viewer who has will see this post and provide some input.

[@llamatone7245]

Thanks for such a great lesson and demo! I found this ESR meter on ebay: MESR-100 AutoRanging In Circuit ESR Capacitor /Low Ohm Meter - should i steer clear of something like this and go with the Blue, like yours. I'm on a very small budet. thanks again.

[@Bbendfender]

Doug, is it a good idea to use a Variac to "bring up the voltage" slowly on an old amp that still has the original electrolytics? I just picked up a '64 Silvertone 1484 and it has not been touched. The amp sounds great. Can I trust the caps that are in it and use the amp for a gig?

[@UncleDoug]

I have used a Variac for this purpose many times, and if you have one, I would recommend using it. I also highly recommend running any newly acquired, untested amp through a light bulb current limiter for its first few start-ups. Re the 1484, I have no way of predicting whether it will function properly, but if it sounds great, without any 120Hz hum, then odds are it will be fine. Until it has proven itself to be trustworthy, you might take along a backup amp just in case. Good luck.

[@jeauxl4051]

Uncle Doug I use the leakage test on my Sencore Z-meter to provide a high impedance, high voltage source at the standby switch of an amp to reform the caps. Power off of course. Another method is to pull the tubes and put a 100K resistor in series right after the rectifier. Measure voltage across the resistor and when it drops down below about 25 volts are so, it is safe to put everything back together and power up the amp. If it doesn't, you know you have a leaky cap and will have to do individual testing to find which one.

[@UncleDoug]

An excellent suggestion, JL. Thanks for your informative input.

[@messmer777]

Question: Is it possible that the filter caps in that amp had been changed fairly recently? Because that can cap looks relatively new. I wonder if you'd measured 1953 capacitors if you'd get the same results. At any rate thanks for the great videos, I've learned so much!

[@UncleDoug]

+Sam Pajanna Sam, the amp appeared to be original and unmolested. There were no fresh solder joints. If the caps had been replaced, it was done long ago. Thanks for watching and for your input :)

[@neutrodyne]

This is an interesting video. I am a retired Technician. There is a lot of hype going on about the F&T caps and they're having a lower ESR rating compared to other brands of the same capacity. I personally can't see any advantage to using them. What are your thoughts on it? I have compared them in circuits to other good capacitors and can't see or hear any difference.

[@UncleDoug]

I can't either, Neutro. I am definitely not a proponent of expensive, "boutique" capacitors. To me, all that really matters with caps is their capacitance and voltage rating.

[@SuperJetjockey]

I just watched this again, and another thought came to mind. I hope you haven't stated it somewhere before, but what is your theory on re-forming electrolytics in a unit that has not been used in some time?

[@UncleDoug]

Actually, I have posted a video showing the benefit of slow start-up of electronic gear that has not been used in a long time....using a Variac. Please check my video list. Reasonably "healthy" electrolytic capacitors can usually be rejuvenated by this technique, while shorted or badly compromised capacitors are simply not salvageable.

[@SuperJetjockey]

I have a variac, and will find the video,

[@joeshmoe7899]

I've seen a vid on YT, an old 70's capacitor with good ESR. But, it was unstable. ESR changed with application of cold spray.

[@UncleDoug]

This sounds credible, Joe, but how often do you cold-spray your filter caps during normal usage of the amp? My concern would be greater if the electrolytic capacitor (the only type in which ESR has any significance) was unstable when normal working voltage was supplied. This is the shortcoming of ESR measurement, in my book, the caps are not stressed by normal working voltage.

[@barrywitt1661]

Uncle Doug, is there any time an Electrolytic capacitor might have an intermittent problem that would not show up with the ESR meter but only when high voltage is applied?Barry

[@UncleDoug]

Yes, it could happen, Barry. It's the one shortcoming of the ESR meter, since it does not test the capacitors in a fully charged state (i.e. detect DC leakage)......however, it can detect faults in capacitors that high voltage might not reveal. The most thorough testing method would be to measure capacitance, leakage at operating voltage, and ESR value.

[@barrywitt1661]

That's what I thought. Thanks for confirming. I have ordered the assembled Anatek ESR meter now that I know how useful it is. Oh, and buy American every body. It may cost more, but it keeps manufacturing jobs here.

[@UncleDoug]

Good decision.....and advice, Barry.

[@jimparker7254]

Wow. I wish I would have ran into this one a while back. Anyway thank you so much. I'm going to have to get one of these before I stare at my magnetone again ( early 460 ). They probably make even better ones nowadays.

[@UncleDoug]

It's a nice tool to have, Jim.

[@claudioarcadexlab6397]

Hi Uncle , good video, but two capacitors in parallel, they are always also with the esr meter, how does the instrument measure only one, without detaching the other from the circuit?

[@UncleDoug]

It doesn't separate the values for the two parallel caps, Claudio, but if one cap has an abnormally high ESR value, it will generally result in an abnormal value for the pair. Then you can pull one end of one out of circuit and determine which one is at fault.

[@claudioarcadexlab6397]

Thanks Uncle, ok, we supposed two caps in parallel, one 1.2 ohm's (ok) and other 4ohm's (bad) (r1*r2)/(r1+r2) = 0.9 ohm's, (0.6 ohm's if they were both ok) , so only 0.3 ohm's of difference, do not you think that maybe they are too few, to notice only, from the measurements, given the tolerances of the capacitors, especially the electrolytics? sorry for the question too detailed, but it is a topic that I am dealing in particular in this period, and I would like to understand if there is actually a reliable way to test the capacitors without removing them from the pcb.

[@UncleDoug]

I understand your concern, Claudio, but you should realize that 1.) Parallel electrolytic caps are very rarely found in vintage guitar amplifiers. 2.) When electrolytic caps "go bad", generally their ESR values are much higher than 4 Ohms. There is generally no evidence of malfunction until the values reach say 10 to 20 Ohms. Granted, a reading of 4 Ohms would indicate that a cap was beginning to fail and ideally should be detected, but once the cap does indeed degenerate into becoming (or verging on) an audible problem, its ESR value will become abnormal, even in parallel. 3.) If you prefer absolute awareness of individual ESR values, however, you really must pull one end of either parallel cap out of circuit, if and when you ever encounter one.

[@claudioarcadexlab6397]

Ok, perfect, now it makes sense, thank you and Merry Christmas :-)

[@charlesshaw9090]

ESR is not an indication of leakage. Also the top two 10μF caps are in parallel with each other, via the field coil winding, which is why you get the same reading for both and why it reads 25μF. It’s clear on the schematic. Always worth checking with the actual circuit before measuring.

[@UncleDoug]

Thanks for your input, Charles. I have learned quite a bit since this video was originally posted.

[@aaronfidelisrecine]

Uncle Doug, I was wondering if you could weigh in on capacitor testing. I have a 3KV DC Power supply that I am going to get up and running in the next few weeks. Is testing a high voltage capacitor by putting DC through it and reading for leakage a more / less / or equally accurate way of testing a capacitor in comparison to the ESR meter? Is it better to do both? Thank you!

[@UncleDoug]

Aaron, due to the extremely high voltage level I would probably opt for leakage testing at 3KVDC, simply because I'm not sure if the ESR meter is capable of providing accurate, meaningful readings for such high-V electrolytics. I have never seen a listing of acceptable ESR values at such high voltage ratings, so you would first have to obtain ESR values from a group of new (known to be good) caps, calculate a mean, and then compare that mean value to the measurements taken from caps that are known to be "leaky". If a significant difference is found, then the ESR meter would be usable to differentiate between good and bad caps. As far as I know, this is uncharted territory, so you would have to verify the reliability of the ESR meter prior to accepting its readings. To be honest, I suggest this with all test equipment.....verify the accuracy before relying on the measurements.

[@aaronfidelisrecine]

Uncle Doug Thanks! I am picking up my ESR meter from Alltronics in Santa Clara this Thursday :) I will let you know how it goes. I have a plethora of old tube equipment that I will be testing and getting running thanks to your suggestion of this great tool :)

[@UncleDoug]

You're welcome, Aaron. I think you'll find the ESR meter to be a very useful device. I also find that the capacitance-reading capability of my digital multimeter, as well as some common sense often come in handy. Best of luck !!!

[@brig.4398]

did you try testing them with a digital meter that shows the value? although I would have done the same thing, if the ESR meter shows ok I'd leave the cap in.

[@UncleDoug]

Yes, I measured the capacitance with a digital meter, but it was "fooled" by two of the caps being in parallel, as is typical of virtually all cap testers (except the ESR meter). The original caps are still in place and working fine.

[@JustSomeGuy1967]

The two were twice the rated value but test fine esr...are you saying the cap value can be ignored? wouldn't that change the function of the amp being twice the cap value? I'm very new to this and just trying to find good practices and I have run across this and would probably change them if they didn't test right across all tests...I have watched all of your videos and for sure you know what the heck you are doing so any advise would be appreciated !! Haven't seen a new video in awhile...everything ok?

[@UncleDoug]

Mark Jordan Everything is fine, Mark. Rusty and I have just been taking some time off. Thanks for asking. The reason the capacitors appeared to have higher-than-proper values was that they were inadvertently measured in parallel (due to their connection in the circuit) by the capacitance meter, which resulted in the addition of the two values together. The reading was not correct. The capacitor values would have agreed with their rated values if they had each been measured by the capacitance meter out of circuit. The ESR meter was not "fooled" by the parallel connection and gave accurate readings.

[@JustSomeGuy1967]

That makes perfect sense...had me pretty confused !! Thanks for taking the time and I'm looking forward to a new video...you are somewhat to blame for my new found interest in all things tube!!

[@UncleDoug]

You're welcome, Mark. This is a very interesting and challenging hobby......welcome aboard :)

[@jeffjeff370]

hello uncle doug ! so happy to see youre still making these videos today! big respect and learning a lot!! but i think the esr meter is not that reable with those high voltages. a higher voltage penatrates more easly thru isolation than the low voltage that the esr is using.just like a piece of dampd paper between a light an a 1.5v battery works as a (bad) isolater but if you touch the wall socket lead with it, its maby the last time that a persoon was standing strait up. or am i false and missing somthing here? I still have the transformers waiting in a closet to start the valco amp build, but my big garden projeckt makes me wait a long time. So sad! hahahaha keep up the good work!

[@kjmcintyrequasisnafu]

When you first power up the old amps, do you connect it to some sort of variac to allow the electrolytic caps to re-form? or is this a dumb question?

[@UncleDoug]

+kjmcintyrequasisnafu It's not a dumb question at all. Yes, if an amp has not been used in several years, it's best to bring it up to operating voltages very gently (over a 20 to 30 minute period) with a Variac. Also, I always use a current limiter with any old circuit of unknown condition, just to reduce the chance of short circuits causing damage. I demonstrate the Variac technique in another video.

[@das250250]

Love these electro magnets for speakers .. I wonder what characteristic they have as opposed to magnets if any ...

[@UncleDoug]

+graham kaveman If you're speaking of electrodynamic speakers, which use electromagnetic coils rather than permanent magnets, their functional properties are quite similar to PM speakers.

[@das250250]

Right , TY. I had a question re capacitors. Do you think there is validity regarding older gear that caps getting older and causing the tone of amps and devices to shift ?

[@UncleDoug]

I think that a significant part of "vintage tone" is the fact that the resistors and capacitors have drifted away from specified values and give a raunchier, more "organic" quality to the tone.....just the opposite of the precise cleanliness of solid state.

[@das250250]

When you say they drift do they alter significantly under normal ambient conditions ? EG As AMp heats up or room temperature changes would these changes be audible to human ear . b) I assume ripping down an old amp that sounds good and measuring the drifted values would make duplicating the warm tones reproducible ?

[@UncleDoug]

I think they have drifted over the years and then drift some more when heated up to operating temperatures. Yes, I think the overall effect is audible. It would be really tough to try to recreate all the drifted values, and impossible to predict their values when fully warmed up. Like an old soldier, a vintage circuit is the product of its lifetime and has countless stories to tell.

[@palpater]

So, I have to ask...Some caps may only fail under working voltage, I wonder if the ESR reading would identify these, with less then 9 volts being pushed from this device?

[@UncleDoug]

An excellent question, Brad. I often hear concern regarding the inability of the ESR meter to test electrolytics at full operating voltage (i.e. 450V). In practical use, this is not an issue for me, since the first step in my evaluation of a newly acquired vintage amp is to check the fuse value and then plug the amp into a current limiter (see my video) and turn it on. If there are no shorts (light bulb flashes and absorbs the current), then check amp function, tone, hum, etc. Remove chassis and address specific deficiencies noted during initial sound check. Test all caps in circuit with ESR meter to see if they are within tolerance. Check resistor values, especially those showing heat damage (esp. screen resistors). Test tubes. Any shorts in electrolytics are immediately evident with current limiter. Any leaky ones are evident (120Hz hum) during full-voltage sound check . Any out of tolerance (failing but not yet failed) are detected by the ESR meter. Thus, the ESR meter is only a part of the process, not the sole means of testing. To address your question, no device can provide complete assurance that an electrolytic won't fail. Even a new, fully tested (at 450V) electrolytic could fail next week; and, fortunately (in my experience) they almost never fail in a "shorted" condition. If they do, then the PT is protected by a carefully selected rapid-blow fuse whose value is just high enough to allow the amp to function properly. This system has worked for me for about 35 years without the loss of a single power transformer in hundreds of amps. The recent availability of the ESR meter has simply made it more comprehensive.

[@TheEDZEPPELINBAND]

GREAT VID i gotta get one of those meters.,...really a great way to go, Uncle Doug- if it works, dont break it.

[@UncleDoug]

+TheEDZEPPELINBAND Exactly, EZ. You will find the ESR meter to be a very useful device. Thanks for watching and commenting :)

[@TheEDZEPPELINBAND]

Hey Uncle Doug- i GOT a meter, and assembled it myself, first project I've ever done, and it works great- it WASNT easy, and I cant tell you how many times I wished I'd just paid the extra 20 bucks,to get an assembled one, cos it's NOT for the timid, but that has never stopped me- and guess what-? i LEARNED a whole lot, by being stubborn- about reading schematics and identifying parts, and i have pretty good soldering skills-

[@UncleDoug]

That's great news, Ed. Congratulations on a very successful project....and result. I think you'll find the ESR meter to be a very useful tool. Best of luck :)

[@jameswallace5967]

I'm going to buy this meter asap!

[@UncleDoug]

It's a good buy, James......very useful for assessing electrolytic caps in circuit (as long as they are not in parallel with other caps).

[@kevinking2468]

Very Interesting - Thanks Uncle Doug!

[@UncleDoug]

+Kevin King You're welcome, Kevin.

[@BoltOnzs]

Hi Doug. Will the Blue ESR meter measure caps less than 1uF? (ie: .01. .001, .002 etc) All of the data that I read says the range is 1uF to 10,000uF . Not very useful for guitar amplifiers except for the power rail caps. Thank you. Rob.

[@UncleDoug]

I believe that all ESR meters are only intended for use with electrolytic caps, RC, so the 1uf lower limit makes sense. I have found, however, that they give consistent measurements with non-electrolytic sub-1uf caps also, but it's uncertain whether this reading provides any meaningful information, other than that the cap is not internally shorted to any degree.

[@BoltOnzs]

Thanks for the reply Doug. I have a Chinese ESR meter that worked very well on all caps of all sizes ($25.00) but I forgot to discharge a cap and it didn't survive. It was only 8VDC too. I bought the Peak Atlas since it reads the capacitance as well so I'll let you know how it works out. Thanks. Rob.

[@UncleDoug]

You're welcome, RC. Being able to read both ESR and capacitance with one device would indeed be an asset.

[@BoltOnzs]

Doug, I've had the Peak Atlas for a week or so and while it does read capacitance and has an auto drain function (up to 50 volts) it will not read non-electrolytic caps like the Chinese MK-328 ESR meter it works extremely well. I ordered another MK-328 and I highly recommend spending $24.00 for the Chinese MK-328 as it does many things that the high end models wont such as reading non electrolytics, transistors, inductance, capacitance and resistance . A simple search on ebay for MK-328 ESR meter will bring up many results. If I use the Peak Atlas for electrolytics and the MK-328 for everything else I'll be fine with no danger of cooking the meter again. Cheers! Rob.

[@jonsanford0]

In the old days it was common to caps like that to be 20% 80% tolerance

[@HeilmanHackatronics]

Great video on old tech.

[@UncleDoug]

Thanks, Matt. Being an old tech myself, it came naturally :))

[@2cool4u24]

You've gotta be careful you don't become the draining resistor. When I was once drained due to a lack of sleep I accidentally had my hand on a non insulated alligator clip while trying to drain a large can cap. My arm hurt for a good hour. Luckily the circuit didn't complete through to the other hand. Always use one hand. BTW. I have the same esr meter. I didn't know you can use it in circuit. Thanks.

[@UncleDoug]

Thanks for the helpful info, 2C :)

[@MuscleDad420]

Hey Doug, bought a 1000uf Sprague Blue Atom ecap recently that I believe to be bogus. Reason being is that the font is different from the others I placed in the same amp. Second reason is the cap returns 0.0 on my Blue Anatek ESR meter. Would you say that is indicative of too-high a value for the meter to display, or a defective cap? Cheers.

[@UncleDoug]

MuscleDad420 Greetings, MD. The only time I ever see a 0.0 reading on my ESR meter is during the initial zeroing procedure. As I recall, a too-high-to-read measurement is usually ----.- I have heard of "counterfeit" capacitors, and this one sounds very suspicious. I usually compare similar caps to each other before installation, and if any stand out from the rest, then they are considered faulty. If the other SBA caps tested out OK, then this one should not be used. If it came, by itself, from a vendor.....I would not buy from them again.

[@MuscleDad420]

Uncle Doug Yes, and my Anatek zeroes correctly. The other SBA's, 3 500uf units in all, tested in the same region relative to each other. The problem I'm experiencing right now in the amp (a solid state Califone amp made by Rheem in the 60's -- yes, the a/c company) is the the signal chokes out momentarily during transient peaks. Experience tells me a bad filter cap is often the culprit here. Any ideas? Think I'll start by ordering a replacement. Considering Mouser charges $15 or so for a 1000uf SBA and this one cost $2 plus + $6 shipping it's highly likely I got fooled by a bogus Chinese copy. Cheers.

[@UncleDoug]

Although I have not experienced the "signal choking" phenomenon you describe, MD, your theory makes sense. Peak output stresses the power supply and would make any weaknesses, i.e. a defective filter cap, evident. It's certainly an easy theory to test....by replacement of the 'suspicious' capacitor and observation of the result. For future reference, please let us know how this turns out.

[@MuscleDad420]

Uncle Doug Absolutely. Already ordered a Nichicon replacement at a reasonable price. What I should have done from the get-go rather than rolling the dice on a $2 Sprague Blue Atom on eBay. The price should have raised alarms. :) Will definitely keep you and your viewers in the loop, especially since there don't seem to be ANY schematics out there for this particular amp. Cheers Doug, love your videos and always look forward to them.

[@UncleDoug]

Thanks, MD, and best of luck with the repair :)

[@NR-bt7yz]

Is that 3 capacitors inside of one can? Does that have a special name? What's the rational for putting them inside 1 container? Do they still make that style?

[@UncleDoug]

Yes, there are three separate capacitors within the single can. I have always just called them "can capacitors".....which seems rather basic, but appropriate. Yes, they are still available but rather expensive, in the $35 range per can.

[@NR-bt7yz]

@@UncleDoug Very interesting, I didn't know that. I discovered they are called "multi section capacitors".

[@UncleDoug]

Yes, indeed. It's good that your curiosity leads you to do research, NR.

[@mechanoid5739]

Out if interest, can you still buy those canned triple capacitors? For authenticity they would look better than three modern cap substitutes.

[@UncleDoug]

Yes, not only can you buy from a wide selection of existing can caps, you can also get them custom made to your own specifications. They are a bit "pricey" however.....but not overly so.

[@mechanoid5739]

@@UncleDoug Thanks for the reply Doug, I did wonder. Love your channel. My brother has been playing in various bands since the 1960's and still does! (He is 72 next month!) He still has his old VOX PA but it hasn't worked for a while. I feel the need to do something about it since watching your wonderful tuition. :)

[@UncleDoug]

@@mechanoid5739 You're welcome, M57. Good luck with your project.

[@sting1111]

I am not sure there is a way to test filter caps at operating voltages. Is it possible they are leaky only at high voltages and pass the ESR test?

[@UncleDoug]

I guess it's possible to get an acceptable ESR value on a leaky cap, but I can't say that I have ever seen it personally. For them to leak at virtually any voltage level, their internal resistance must be reduced to some extent.

[@emergencynurse02]

Thank You! I have an old Traynor I want to test his way...

[@UncleDoug]

You're welcome, GH. I hope it checks out OK for you.

[@williamolsen20]

I think the reissues of these amps have solid state rectifiers. I also think it only has one power tube, and one preamp tube. I had one it was not very nice from what I remeber.

[@UncleDoug]

You could well be right, William. Older tends to be better :)

[@iamdarkyoshi]

I got a tester on ebay for 30 bucis, it does capacitance, esr, as well as transitors, mosfets, inductors, resistors, diodes, zener diodes, dueldiodes, and quite a bit more. It also has a nice graphical screen.

[@UncleDoug]

That sounds like a versatile instrument at a very reasonable price, Luke. Congratulations on a great acquisition :)

[@iamdarkyoshi]

Uncle Doug yup. I got it the other day actually. I wish I would have gotten one earlier, it works so well. It uses an atmega 328 series chip, same as the arduino uno. It also has a port to program the latest firmware. I will complain that it does not have a way to calibrate (that I am aware of)

[@UncleDoug]

It really sounds like a good instrument, Luke. The lack of calibration capability is a little troublesome. Perhaps you could make a graph with instrument readings on the X axis and known-correct values on the Y axis, then either calculate a correction factor or use the graph to correct the readings.....if necessary. On the other hand, you may find it to be completely accurate.

[@iamdarkyoshi]

I would have to say it is pretty acurate, it has no wires. There is a componant socket on the board, and the chip is right next to it. This helps with wire induced noise and resistance.

[@Kalkaekie]

Very interesting and helpful video !! Thanks !!

[@UncleDoug]

You're welcome, Kal.

[@bastardbus]

I own and religiously use a HeathKit I-28 Vacuum Tube cap tester. It will measure any cap values and leakage up to 600V. I have seen much claim how wonderful these new ESR meters and pondered buying one but I am curious will the ESR meter test any size capacitor and will it test caps under full voltage load? Is there any benefit to the ESR meter over the old tube style cap testers?

[@UncleDoug]

Greetings, BB. I use the ESR meter for both electrolytics and non-polar caps ranging from .01uF up to 100uF at 475VDC. You should check with Anatek to see what they claim its range to be. I know it's generally recommended only for electrolytics, but I have found it to work with non-polars as well. The advantage is that it tests the capacitors in circuit without concern for error induced by nearby components (i.e. other caps in parallel). No lifting one lead or removing the cap from the circuit. You can check all the caps on a circuit board or in a chassis in a matter of a minute or two. It does not fully charge the capacitor during testing, which some people find worrisome, but I have yet to encounter a capacitor that tests well with the ESR meter and yet has an internal short....or the tendency to develop one. Bad caps generally produce readings that are obviously unacceptable.....there is no "splitting of hairs", and if a cap tests well, it's (so far) OK. The ESR meter is not my only means of assessing caps, but a part of the process. I also measure capacitance with my DMM, use a Variac slow-start with circuits that have sat for years, and always use a Current Limiter when energizing a circuit for the first few times.

[@bastardbus]

Uncle Doug I have been doing some research on the subject and have been told that ESR will give false readings on caps under 1uf. Having used an actual cap tester extensively I have found the majority of old paper caps do not internally short but have leakage under load. Majority of the time the cap will test within spec but leak voltage at 25, 50 or 100 volts when the cap is rated for 400V or 600V. Obviously the cap is bad and on it's way out and guessing would not be caught by the ESR meter. I would be very curious to compare some good and bad caps of varying degree with a cap tester and an ESR meter. I posted this question to the ARF forum and came up with some very informative answers from regarding the subject. Here is the link to the thread antiqueradios.com/forums/viewtopic.php?f=8&t=264574 BTW great videos and information you do! I really enjoy them.

[@UncleDoug]

Greetings, BB. I'm glad you enjoy the videos :) I followed your link and read the comments. I am aware of the perceived shortcomings of the ESR meter and, as I said, do not prescribe it as the one and only way to test electrolytic capacitors....however, in daily use, I still find it to be a very helpful tool when working with vintage electronic gear, and occasionally demonstrate its utility in my videos. I have also documented its ability to accurately measure the capacitance of non-electrolytic caps, in circuit, from .01 to 1.0uf. As with any tool, the ESR meter has applications and limitations, but to those of us with hands-on experience with the device, it offers a quick and effortless means to check the status of capacitors in a way that no other methods can duplicate. Thank you for your thoughtful inquiry and comments. Viewers like you make this process worthwhile :)

[@brig.4398]

Bastard Bus what I did is make up a chart and taped to the back of my ESR meter, I measured some new caps an wrote down the readings. So I know what to expect when I testing caps with my meter.

[@jeauxl4051]

Mister "Bus", ESR is not a measurement that is tested under voltage so the reading the meter gives is accurate. And there is four main properties that determine the quality of an electrolytic capacitor - Value, Leakage, ESR and Dialectric Constant. Dialectric Constant, which is the tendency for a capacitor to act as a battery, is not really a concern in guitar amp use. With your ability to check the other three properties by getting the ESR meter, you won't have any doubt whether a cap is good. I have a Sencore Z-meter that checks all four parameters and I'm like Doug, I don't change caps just because they are old if they check good now that I have a good meter.

[@cat-lw6kq]

I thought those capacitors go bad just sitting on the shelf if they aren't in use. I have an old signal tracer from 1949 and I'm just going to replace all the caps to restore it. I'[m not going to bother to test them.

[@UncleDoug]

Everyone has their own opinion regarding electrolytic capacitors, Cat. Do what you think is best.

[@cat-lw6kq]

Watching your videos, learning some things. I wonder if that amp had been in storage for a long time would that make a difference? I have some old oscilloscopes, one from the 1970s and they work great, I've never replaced any parts in them. I think you're right about that old capacitor being better quality.

[@UncleDoug]

If you have a Variac, Cat, you can slowly bring up an old circuit to full operating voltage, and allow the electrolytic caps to "re-form" and essentially heal themselves. Radio repair people do this all the time. If a cap fails to re-form, then you can replace it.

[@cat-lw6kq]

we used to have one. closed our shop some years ago. thx for the videos.

[@TRONMAGNUM2099]

I like to test high voltage caps with an insulation meter. Sometimes caps pass at low voltage but short at high.

[@UncleDoug]

Thanks for your input, TM.

[@MrRadioGypsy]

Yeah, I will replace caps if either the ESR is out of spec, or if they are out of uf tolerance. The latter is usually a sign of drying out, and would just rather replace them than having to take it all apart for a second time . . .

[@rillloudmother]

Those guys by the beach in Clearwater wanted a lot more than $100 to use their E-Meters...

[@thermionic1234567]

Just saw this old video which I realized I’d never seen. Hope I’ll see Rusty in it. What a wonderful dog! Is your mourning period over? You need a new dog!

[@UncleDoug]

Thanks so much, Jeffrey. We still miss him, but much of the pain of his loss has subsided. I want another pup, but my wife resists it.

[@thermionic1234567]

Uncle Doug Mine too! Maybe if you get her a small, fluffy, white dog with a French name, preferably ending in “doo” or “poo?” She probably wouldn’t be able to resist...

[@UncleDoug]

I don't know, Jeff. Her last two dogs were full-size Collies, so I'm not sure if a little pup (which I honestly prefer) would do.