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looking to buy a in circuit ESR tester

Discussion in 'Amp Tech Center' started by avspecialist, Oct 18, 2020.

  1. avspecialist

    avspecialist Tele-Meister

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    Im looking for some advice to purchase an electrolytic ESR meter. I see the blue one used by Uncle Doug is on amazon fully assembled for $116.95. It looks good and simple enough to use. I was wondering if there were any better choices for checking the electrolytic caps in circuit, thanks in advance, Bob
     
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  2. Phrygian77

    Phrygian77 Friend of Leo's Gold Supporter

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    I have one these cheapies. It seems to work fine.

    IMG_20200919_114429.jpg

    IMG_20200919_114504.jpg

    IMG_20200919_115623.jpg
     
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  3. BobbyZ

    BobbyZ Doctor of Teleocity

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    I don't have much faith in a tester that runs on a 9 volt battery when testing 450 volt caps. Just buy the cheapest one you can, if you want one.
    Closest thing I had to that was the capacitance setting on a multimeter. Unbelievable how filter caps spilling their guts all over still test pretty good for capacitance.
    Back in "the day" the best test was substitution, I believe it still is. Never once put an old electrolytic back in an amp.
     
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  4. Jon Snell

    Jon Snell Tele-Holic

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    Checking 'in circuit' will add errors caused by other components and I would not use that system.
    I use a DE-5000. I can set the desired test frequency of 100HZ up to 20kHZ. 100HZ is no good for a 220p capacitor and 20kHZ is no good for a smoothing capacitor designed to work at mains frequency. Screenshot 2020-10-18 at 18.47.30.png Screenshot 2020-10-18 at 18.47.49.png Screenshot 2020-10-18 at 18.48.07.png Screenshot 2020-10-18 at 18.48.21.png This will enable an accurate evaluation but not with other components across the device being tested.
    The device on test in the picture is a 33u capacitor and shows up as 34.53u so pretty close to manufacturers tollerance.
     
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  5. Phrygian77

    Phrygian77 Friend of Leo's Gold Supporter

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    The ESR test doesn't need to run "at voltage". It is an AC test after all. In the case of filter caps rated at 500VDC, that is a DC rating, not AC.

    The cap at the testing frequency should still have the lowest impedance in the circuit, unless something is wrong with the circuit. Were talking a couple of ohms vs hundreds to thousands of ohms, so does it throw the test off slightly, yes. No, you're not going to get an accurate ESR reading in circuit. However, it does let you quickly determine if a cap has a higher than normal ESR in circuit.
     
  6. Phrygian77

    Phrygian77 Friend of Leo's Gold Supporter

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    That was the reason I showed a picture of a cap tested out of circuit vs the cap in circuit.
     
  7. avspecialist

    avspecialist Tele-Meister

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    thanks for the info Phrygian77, I looked at that one on Amazon $60.00. i’m leaning in that direction over the blue one, I’m not overly concerned with the price, I’m just looking for reasonable accuracy. I think it will make a great addition to my home bench.
     
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  8. avspecialist

    avspecialist Tele-Meister

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    After going back and forth on ESR meters I decided to get this one, because it had a lot of good features, I hope I didn't make a mistake. I bought it on Amazon $ 129.00

    DER ESR Meter.jpg
     
  9. Jon Snell

    Jon Snell Tele-Holic

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    You won't be dissapointed.
    Hows your Chinese reading ... luckily there is a manual online in English.
     
  10. avspecialist

    avspecialist Tele-Meister

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    thanks for the link, I only know how to pick from column A and B on the menu!!!! :>)
     
  11. Phrygian77

    Phrygian77 Friend of Leo's Gold Supporter

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    I like the longer shielded leads. A see people complain about the regular short leads on most of them. Well, it's testing at RF frequencies! Use your head! Lol
     
  12. radiocaster

    radiocaster Poster Extraordinaire

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    I have quite the opposite experience, caps look fine, test at half capacitance (for ex, 10 microfarads instead of the printed 20) for caps about 25 years old

    On the other hand, most of those tested fine for ESR.

    Not saying don't get an ESR tester, it's an extra tool which can be useful.
     
  13. avspecialist

    avspecialist Tele-Meister

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    I have the meter, downloaded the English manual, now Ill get to testing tonight.




    DE-5000 ESR meter.JPG
     
  14. BobbyZ

    BobbyZ Doctor of Teleocity

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    Only 25 years old?
    I never work on amps that new. :)
     
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  15. LightningPhil

    LightningPhil Tele-Meister

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    On some the frequency is selectable which is quite handy. Generally tops out about 100 kHz which counts as the bottom end of RF. A radio that pops to mind using a lower frequency is the Nicola cave rescue devices. They’re about 50 kHz and designed to send voice and text messages through several km of rock! Submarines use even lower frequency systems or at least have done. Cool stuff.

    Ideally not using leads and clipping the items to be tested directly into test slots on the meter is best. A 4 point measurement using a set of cables designed for this is the next step does in accuracy. And a 2 wire, 2 point measurement is more effected by leads.

    Leads are floppy which allows the distance between them to vary, which acts as a random value small capacitance in parallel with the item under test. Any loop created by the leads increases inductance. So moving leads together can eliminate most inductance at the cost of increasing capacitance. Fortunately the capacitance and inductance issues are in the low 10’s of pF and nH/uH range for a usual 1 m long set of 2 wire test leads.

    But then there’s contact resistance and the resistance of the leads. This will stuff up any low resistance/impedance measurement with a 2 wire 2 point measurement. Generally I assume the leads could have a fraction to a couple of ohms of resistance - as could a point contact to old component terminals if lightly corroded (even invisibly).

    To summarise the babble above, 4 point measurement is essential for low resistance/impedance measurements. Ideally don’t use leads, but if you do, use ones that came with the meter.
     
  16. LightningPhil

    LightningPhil Tele-Meister

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    It seems we’re mainly concerning ourselves with electrolytic scraps here. An insulation tester is pretty handy at telling whether one is leaky or not. Do bare in mind that they will charge up a capacitor under test. So it’s a good idea to put the cap into a small vice, test it and then discharge one way or another with a resistor. And then wait a short while, measure the voltage across the terminals, be amused that it’s not zero, discharge again and then quickly wrap some wire around the terminals to keep it shorted.

    Dielectric recovery is a real thing. It occurs when charge has leaked into the dielectric and then reached some sort of equilibrium. Then when the voltage on the plates changes, the charge in the dielectric has to re equalise. This can take a while in some caps and I’ve seen this in all types of caps. It’s particularly problematic with ageing industrial phase correction or pulse power capacitor banks (substation scale, weighing many tonnes). Where operating voltage is in the high thousands, dielectric recovery can be in the hundreds to low thousands. Quite lethal and makes for good sparks when switches close.
     
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  17. Jon Snell

    Jon Snell Tele-Holic

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    Using my DE5000 with the aditional lead box, when testing less than 15pF at 100kHZ there is a few pF variation depending upon the dressing of the leads testing the capacitor, this of course can be nulled out at the simple press of a button.
    Bo concerns there and especially if testing in the uF scale, not even noticeable as an error.
    There is a handy matching within setting allowing to state a +-1% of preferred value if needed for batch samling.
    Nice machine.

    Needless to say, components cannot be measured accurately in circuit unless they are not connected to other components.
     
    Last edited: Oct 30, 2020
  18. avspecialist

    avspecialist Tele-Meister

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    Hi Jon and Lightning Phil: I received my De5000 meter yesterday and I did some preliminary testing of new capacitors to see how the meter worked. I'm still learning about it. I bought it to test an amp I accidently touched my probe from the fuse holder to pin3 on one of my power tubes. Now the amp has some issues I'm trying to track down, see:
    Shorted Pin 3 to Fuse holder, now problems

    Thanks for jumping in and helping, Bob
     
  19. Jon Snell

    Jon Snell Tele-Holic

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    The learning curve on the meter is very steep but you will soon get used to it.
    Remove one leg of the component you with to test, from the rest of the circuit. That will give an accurate reading.
    (Don't forget the ESR setting is not designed to display in the Auto mode, pressLCR Auto button twice to get the ESR value).
     
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  20. avspecialist

    avspecialist Tele-Meister

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    45FB6684-4546-4B51-ABF9-107BA2AE1FC3.jpeg Hi Jon: i started my first testing today. first cap left under doghouse: Sprague Adam rated at 20uf @500V tested out of circuit at 100k frequency measured 2.02 ohms and 0.525uH, middle out of circuit 2.04 ohms and .527uH, right measured out of circuit 1.89 ohms and .512uH. I tried in circuit the 2 80uf at 450. left measured 0.40 ohms and .008uH. and the right measured .46 ohms and .001uH.

    I’m not sure how good or bad these caps are based on the measurements, they about 4 years old
     
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