How To Test And Measure The Working Rated Voltage Of A Capacitor. Find Fake Capacitors
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- Опубліковано 11 вер 2023
- Some time ago I had a problem with some replacement capacitors I was using to repair a Peavey PA Amplifier. They were not working correctly and I suspected they were fake capacitors. So how do we test for example if a 100V capacitor rally is rated at 100V? Well let's find out...
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Thank you
Richard
Very interesting to see a controlled way of testing working voltage. Always thought it was like testing fuses. You could find the rating, but it didn’t matter as the test would kill it.
The first test is exactly how you reform old electrolytic capacitors. You don't blow the component up because you're always monitoring the current. Current is always what kills everything in electronics. Current is what kills everything period. The whole it's the current that kills ya deal.
Now there's a project for you. I'm sure that between you and Det, you could design a circuit that would increment a variable voltage until a predetermined current is detected, stop and display the result. Simple!😄
Cheers, EJ
Very Nice Richard, thank you, have always only tested the capacitance but never thought much of the nameplate voltage value as being "testable".... Again, another thing I was able to learn! Thank you very much.
Glad you liked it
What an excellent demonstration showing the importance of testing at (working) voltage which many of the contemporary capacitor testers simply don't do. And what's more the needed devices are readily on-hand to anyone with a half-way decent electronics workbench.
What a brilliant little test! Thanks for sharing 👍
If we take the maximum working voltage as that at which leakage starts to occur, then if we push the cap above that slightly, then disconnect, the leakage will still be occurring and will drain the voltage down, to a point at which the leakage stops, at that point I suggest it is at its true maximum working/breakdown voltage, ie the leak behaves like a resistor and zener diode. with the final example shown in the vid the capacitor reached 100v but only with a substantial 30ma of current, without the 30ma the voltage within just a few seconds sagged back to 90, I'd suggest from that the true safe maximum working voltage would be 90v-10%, or 80v for trouble free operation.
I have never seen this method before but I like it, and is something I will remember to do whenever I buy a new bag of caps to restock my draw. Thank you for this informative video.
CORRECTED EDITED & FORMATTED TEXT:
Pay attention to the difference and formatting
If we take the maximum working voltage as that at which leakage starts
to occur - then push the cap above that slightly - then disconnect --
the leakage will still be occurring and will drain the voltage down to
a point at which the leakage stops.
At that point I suggest it is at its true maximum working/breakdown
voltage - i.e. the leak behaves like a resistor and zener diode.
With the final example shown in the video the capacitor reached 100v
but only with a substantial 30ma of current.
Without the 30ma current - the voltage sagged back to 90v within just
a few seconds - I would suggest from that finding - the true safe
maximum working voltage would be 90v-10% or 80v for trouble free
operation.
I have never seen this method used before - however - I like it - and
it is something I will remember to do whenever I buy a new bag of caps
to restock my supply. Thank you for this informative video.
Very nice way to measure leakage of old caps. Now i can measure capacitance esr and leakage. It’s possible to a cap having good esr, good capacitance and still have leakage.
Hello, am from Uganda, Africa, am an electrical technician and am so greatful to you man.
U have tought me more than what i learnt in electrical school.
Can u please do a video on igbt welding machines
Very handy.....many thanks, Richard.
I have loved your way for testing the capacitor with the risistance .🎉🎉🎉🎉
Actually, credit where it is due, that tweak was by Carlos @retroupgrade
Very useful info. Thanks! 😀
This is basically doing a capacitor leakage test. They used to make instruments for this back in the day, Mr Carlsen's lab has quite a few videos on such things.
So useful, so simple.... so genious ! 👍
Thanks. Excellent video
Heya that's a nice way to test them thanks for the lesson
Great idea, why did I never think of that?! It would be interesting to see the results with an electrolytic connected the wrong way round.
yeah it would be interesting , we will try that on the electronics channel next time , wonder if it breaks down earlier or same voltage in reverse
They pop open with great force and display their innards; some would say EXPLODE with a flash-bang. Use a high voltage, high current PS and arrange a safety shield, ventilation and eye protection. It gets messy with oily fine debris plastered everywhere. ( I was quite dangerous 50+ years ago, LOL )
Interesting test for sure.
Thank you, this was very useful, the world of capacitors, or maybe it's the underworld.........
You can use a similar setup for capacitor reforming. The process is to slowly step up and ensure current stays low. I personally use a (cheap) adjustable mains transformer (after an isolation transformer) and a little board with a bridge rectifier, (known good) smoothing capacitor, power resistors and an additional diode before the "payload" capacitor. I don't do current sensing on my setup like you, just using a normal amp meter.
Very nice Rich and Carlos... I like using the variac with the bridge rectifier . Obviously the AC output voltage on the variac will be different than the DC rectifier output . Just something to consider when taking measurements ..
Yes, with the variac method you have to measure the DC voltage across the capacitor as you can only read AC on the variac. If you want to get a precise reading of the break down voltage of the capacitor, take a second multimeter and also read across the resistor. And who doesn't have at least two multimeters these days 😉
@@LearnElectronicsRepairMy Fluke doesn't havea uA measuring range. My Lidl cheapy DMM does, so occasionally I use that one, provided that the voltage on the project is comfortably low.
maybe also add a second dmm to measure current. great info as usual. thank you.
Capacitors are wonderfully complex little beasts. This article shows the importance of good design. Once the type of cap has been chosen and as long as the footprint is manageable the rule of thumb is spec at least double the expected voltage or better still 10x. This is easier to do with semiconductors of course but getting better than you need is rarely a bad idea. Now I will not only use 50v for a 12v supply but confirm they really are good at that voltage.
Two layers of aluminium foil with a dielectric in the middle and rolled up like a Swiss roll is wonderfully complex?
Wonderfully simple more like.
And don't get me started on air cored variable capacitors.
@@deang5622The technology might be relatively simple ( formulations of the electrolyte are anything but simple) , but the behaviour can turn out to be complex.
Agree, it's the way he did it to.
in the 80s we used to do a lot of set top boxes mainly PACE mainly frome blown up caps
even braned ones from well known makers used as replacementswere bad so we had a death box to test them before fitting. .this was the start of the bad caps era
Good manufacturers were never impacted by capacitor plague. That was caused by industrial espionage and bad electrolyte formulations. Good companies never bought dodgy electrolyte. They already knew how to make it right.
@1pcfred um Sony Samsung Canon pace to name a few makes that had short lived electrolytic caps that damaged board tracks and smelt of fish
@@robtitheridge9708Yeah there was a (brief) period when even the Japanese caps were failing in large numbers. It didn't help the industry one bit, coming as it did when the Chinese onslaught was getting into gear. If that expensive Sony was failing after a couple of years as well, there was little incentive to spend more.
Hello, thanks for your content, just found out about it. I was wondering how we can go about repairing any piece of electronics we have? For example a device with a battery no longer charging
Must admit I've just tested batches of suspect caps in the past by blasting them with voltage plus 20% direct from a power supply. I can live with blowing a few up! Oddly enough I've found that "fake" ones (by this measure) are fairly rare.
Lets have little fun and do the same tests with Tantalum capacitors.🤯
OK why not. We will do this on the next live stream. Sunday 24th Sept 17:00 London UK time.
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Flames
What about old capacitors that may need a bit of re-forming - wonder if the aliexpress ones you got were old and needed a gentle reform before operating at their working voltage - I think there is current flow during reforming of the oxide layer so this measurement method to determine rated working voltage quickly may not reliably find the actual working voltage; It would show a fair leakage current but I would expect this to go to pretty much zero - may take a fair amount of time though (hours?) as reforming should be well current limited.
Nice, I'll have to remember this, also, could this method reform caps out of circuit for vintage equipment if 1 doesn't have a variac??
Seen Fake Batteries too...
Nice RIchard, so you bought the very same capacitors again at ALI and found some good ones? I guess if they are cheap enough you could sharpie mark them at a lower working voltage and use them elsewhere (or just dump them in a lower voltage drawer for use in your case.)
I use this to check amp PSU caps but recently decided to check esr afterwards and yes I didn’t discharge cap and destroyed my esr meter 😩 .. we all do stupid things sometimes guys!
Do not test above the voltage rating because when you go until the voltage does not go up anymore, the current goes up a lot and this damages the oxide layer and you kill the cap.
I build two testers for checking this, not for fakes, I only order from companies like Farnell, mouser etc, but caps fail for 3 things and max/min values are in the datasdheets 1) a high DF (tan delta, ESR) this is the ESR at 100/120 Hz (not at 100 kHz) 2) DC leakage 3) Capacitance at 100 Hz. If the capacitance dropped to much, most times the DF is to high. Leakage is more or less a stand alone thing. C and DF kan be good but it still leaks to much. Leakage is something that is for most a problem for caps over 100V. The factory forms the oxide layer often at a higher WV, osometimes even twice the working voltage.
Cap-meters without DF/ESR/Q are not measuring the complex impedance and are not good to test used caps because the faults often cause a incorrect capacitance reading. DMMs are only good for new caps, bad caps often read good until they are more than bad (a popped cap was long before the popping already bad)
Does this work for tantalum capacitors? Ceramic capacitors? I have many take-off capacitors that don't designate or code their voltage rating. If this is a valid non-destructive way to evaluate those as well I would like to implement it where appropriate. I saw on another video that this procedure you use is also recommended for "reforming" capacitors before use. Thanks for your helpful comments. I'm getting back into repair and am now equipped with an LCR meter and other equipment I never had before.
You seem to make videos about very specific use case, and it would be very helpful if you could make videos to learn the general skill of finding device fault for repair. Thanks again for your consideration!
Give me a specific example of what you would find helpful
@@LearnElectronicsRepair I see what you did there...
Sir could u please make a video on how to test capacitor in circuit
A good old fashioned swing meter is better for checking caps and inductors.
If current doesn't matter, there are boost modules that go to 600V - I have one somewhere, and I think it was 5V to 600V -.
👍👍👌👌
I have a computer motherboard with one blown capacitor 16v 1,000 uf. If this cap blew, could it have damaged any other components next to it?
If you don't need a lot a lot of current, could you perhaps build something using a simple voltage multiplier from some capacitors and diodes to test higher voltage capacitors (e.g. 450V for PSUs with active PFC)?
The only problem I can see with the asked question is, you need to be able to "vary" that output voltage which could be a bit of a pickle, you could theoretically use each step of a Cockcroft Walton multiplier and test that way...... But....... Doing it wrong could hurt you, the capacitor or maybe both.... And, 450 volts with a rapid discharge is a couple of Joules....... So, be very careful....... If, you do something like that........
@@GapRecordingsNamibiaYes, I learned that the hard way with a 1000uF cap charged with 330V passing current between two fingers of one hand. It was like I was hit hard with a whip. No permanent damage to my nerves fortunately😮💨.
@@GapRecordingsNamibia ... but shirley? Can you not do exactly what has been done here but with a box with a LCD that slowly raises the voltage until the current starts up and then shuts off and displays the achieved voltage? The cap could be enclosed in a perspex box in case it does something fun? There are commercial testers already out there like the Supco MFD10 Digital Capacitor Tester - sans shield of course.
That is the same setup you use to reform a capacitor. You step up the voltage slowly until the current drops to zero then keep stepping the voltage up. Once you hit the working voltage you hold it there and let the oxide layer form. As far as your second method goes the other capacitors broke down at microamps. So I'm not so sure your second method is entirely valid. Being as that screen tester supplies milliamps. You could add a resistor to it and measure like you did in the first test though.
I did mention this in the video, though I am not convinced 30mA for a short period of time would kill the capacitor. In the way I used it, to test if the capacitor could at least handle it's rated voltage plus a few percent more rather than trying to find the actual breakdown voltage I think it was a useful enough test and also safe for the capacitor. Your idea of adding a resistor isn't really going to help with the backlight tester, as it can supply over 320V and would just continue to increase the voltage until either it was supplying 30mA or the voltage topped out yes?
@@LearnElectronicsRepair when you calculated the breakdown on your first test you were measuring microamps. Which your screen tester can't show. To really see what's going on you have to add the resistor shunt like you had in your first test. Just seeing the screen tester meter counting up voltage isn't enough. You could still be leaking those same microamps and it can keep going. Because it can supply milliamps of current. So leaking some microamps won't phase it any. It's the this is fine meme.
@@1pcfred That's a fair comment and I don't know the answer so let's try it on the next live stream. Together with someone else's comment that you can't (or shouldn't) do this test with Tantalum capacitors. The live streams are on the sister channel in collaboration with Carlos and Detlef, next one is Sunday 24th Sept, 5pm UK time. Be sure to come and join us www.youtube.com/@theelectronicschannel
@@LearnElectronicsRepair tantalum capacitors = tantrum capacitors. I wouldn't recommend using tantrum caps for anything. I've seen too many blow up. I've seen them sweat little silver beads right before they pop. I think they do the sweat thing if you reverse bias them? But after a bit it'll still explode. So don't watch it too closely.
Hi Richard. Happy New Year 2024! I certainly learned a lot. Thank you very much! Regards from Australia, Jerry.
The schematic drawn on paper is wrong , multimeter should be connected in parallel with resistor not with capacitor .
Where did u find a literate bigfoot?😁
I would have expected a 25V rating to work at about 1.5times to give margin, not give up at 27V.
BATTERY 1.5 50
I detest hse morons.
But a note here.
This is GREAT, but be careful with Tantilum caps!
Is this a non-destructive test?
Yes, providing you don’t increase the voltage in big steps and once you find the break down voltage you don’t continue increasing beyond it.
Yes, you saw in the video I had 625uA running through the first capacitor when I exceeded the breakdown voltage. On the second one I didn't calculate it but it was much less, probably around 200uA
@@LearnElectronicsRepair Why not include some of your FAKE or FAULTY capacitors in the demonstration?
A safety caution and a little bit of nit picking 🙂
7:20 When using Ohm's law, it's not V = I x R , but U = I x R .
Most of us know this, but for beginners in Electronics, that can be confusing when using V instead of U as unit voor Voltage.
Regarding the measuring of the working rated voltage, your methods are fine, but only if you did previous a ESR measuring.
Bad capacitors can show there real capacity when using a DMM, and sometimes even a higher capacity then normal, but they can leak like crazy and you won't reach there normal rated working voltage, because they start leaking much sooner before they reached there normal rated working voltage.
So without a ESR reading, you coult then assume that the working rated voltage is much lower then printed on the capacitor, while the capacitor is just bad.
Only when a ESR measuring show normal values, you can proceed with the voltage test like you showed.
And last, a big safety caution when using big capacitors or batteries connected to a powersource. It's always better to disconnect the leads from the capacitor or battery, before switching of your bench power supply or the LED backgroundtester, because when you leave the leads to the capacitor connected during the switch off, you are backfeeding the capacitor into your power supply. If your power source contains a linear voltage regulator, and the manufacturer placed a diode in bypass over the in and output of the voltage regulator, you are good, but if not, you can destroy this voltage regulator due the reverse current flow that a capacitor or battery creates.
And a big capacitor with 100V and that amount of capacity, can blow many things up.
I was taught v=I × R where did u get the u from?
People use V, U or E for voltage. U is often used in countries with Germanic languages (Scandinavian countries, Germany, Holland, Belgium,...).
@@kriswillems5661 Agreed, the english language is V not U. The use of the letters in the equation will depend on your country of origen....
Sorry, not true. The use of the letters in the equation will depend on your country of origen. In the english culture or derivative languages V is the correct term, in Germanic or Scandinavian language origens, U or E have been designated... Although I have very rarely seen E and mostly U...
A safety caution and a little bit of nit picking 🙂
7:20 When using Ohm's law, it's not V = I x R , but U = I x R .
What others said. Ohms law is V=IR, or if it isn't then all those books and electronics magazines I read in the 70s and 80s, the full time C&G course in Electronics repair I took and a lot of other people over the years were talking rubbish.
Regarding the measuring of the working rated voltage, your methods are fine, but only if you did previous a ESR measuring.
Bad capacitors can show there real capacity when using a DMM, and sometimes even a higher capacity then normal, but they can leak like crazy and you won't reach there normal rated working voltage, because they start leaking much sooner before they reached there normal rated working voltage.
So without a ESR reading, you coult then assume that the working rated voltage is much lower then printed on the capacitor, while the capacitor is just bad.
Only when a ESR measuring show normal values, you can proceed with the voltage test like you showed.
I've made videos about bad ESR and also shown capacitors that read perfectly good ESR and twice their rated which are very leaky. But really I don't see your point. Either way, bad ESR or bad voltage test, the capacitor is still bad. Prove it either way you like, it's still going in the bin.
And last, a big safety caution when using big capacitors or batteries connected to a powersource. It's always better to disconnect the leads from the capacitor or battery, before switching of your bench power supply or the LED backgroundtester, because when you leave the leads to the capacitor connected during the switch off, you are backfeeding the capacitor into your power supply. If your power source contains a linear voltage regulator, and the manufacturer placed a diode in bypass over the in and output of the voltage regulator, you are good, but if not, you can destroy this voltage regulator due the reverse current flow that a capacitor or battery creates.
And a big capacitor with 100V and that amount of capacity, can blow many things up.
Agreed, though it depends like you say on the design of the bench PSU.
You can't measure the rated voltage of a capacitor, it is what ever the manufacturer says it is. You are measuring the breakdown voltage. A capacitor that is rated by the manufacturer to 100 V but breaks down at 10 V is still rated 100 V even if it is faulty. Rated voltage is what the manufacturer claim it can whitstand regardless of what it actually whitstands.
Just like you can't measure the nominal resistance of a resistor, only the actually resistance.
It's a stress test, not unlike the calculus paradigm where you keep taking half steps towards a wall but never quite reach the wall. For a correlation to resistors, you would track the resistance change to power. If you were sold a 2W resistor but it goes out of resistance tolerance spec at 1/2W, then you have determined that the resistor is not worthy of the specification. I think that is the point being made by the video.
It's Chinese so the capacity figure printed on the case is 10x the real capacity. Because greater capacity in a capacitor is better, right?
1:16 That capacitor has a marking on it that tells you it's a bad capacitor. ''ic'' stands for ''This Capacitor Is A Bag Of Shite And You Should Replace It.'' People who have a very poor grasp of the English language will say that ''ic'' stands for Illinois Capacitor. 😜