0 Ohm ESR ?? - Testing cap in PSU

[aneng]

Hi...

I'm attempting my first ever SMPS repair and I'm testing a cap that would give me the symptoms I'm getting if it was faulty.

I have one of those cheap 'TC1' component testers that tells me the 1000uF cap is 941uF but has a zero ohm ESR (removed from the board).

Do I believe that ESR reading ? Is the cap shorted ? How do I confirm whether it's good or not if I can't trust the component tester ?

Many thanks !

Kev.

[stj]

Re: 0 Ohm ESR ?? - Testing cap in PSU

if it was shorted it wouldnt read the capacitance.
it's probably out of range - the meter wont show esr above a certain point.

[aneng]

Re: 0 Ohm ESR ?? - Testing cap in PSU

So you think that because it says zero ohms ESR, that it might actually be infinite instead and therefore the cap is bad ? Is that what you mean by 'out of range' ?

[spiros.p]

Re: 0 Ohm ESR ?? - Testing cap in PSU

same here..measure some caps from instalation power amp and no readings from esr.only 1300mf down from nominal capacitance(6800mf is now 5500mf)on extech LCR meter.

[budm]

Re: 0 Ohm ESR ?? - Testing cap in PSU

Hi...

I'm attempting my first ever SMPS repair and I'm testing a cap that would give me the symptoms I'm getting if it was faulty.

I have one of those cheap 'TC1' component testers that tells me the 1000uF cap is 941uF but has a zero ohm ESR (removed from the board).

Do I believe that ESR reading ? Is the cap shorted ? How do I confirm whether it's good or not if I can't trust the component tester ?

Many thanks !

Kev.

Try measuring other large value caps you have in stock and see what you read. Did you also verify that the cap is completely discharged?

[momaka]

Re: 0 Ohm ESR ?? - Testing cap in PSU

I also have one of these cheap cap meters / multi-testers (not "TC1", but rather an older GM328 variant), and it does the same thing when I measure caps between test pins 1 and 2. In fact, the manual/menu calls for measuring electrolytic caps between pins 1 and 3... but then I always get a slightly higher-than-normal ESR on most caps. So I have to pick either between slightly under-reported ESR between pins 1 and 2, or slightly over-reported ESR between pins 1 and 3. I've calibrated my meter many times, but this hardly changes. So I usually go with the former... and so far, that hasn't been an issue at catching bad caps.

Ideally, you shouldn't be using these cheap testers to check a cap's ESR against the one in the datasheet. IMO, these testers aren't really accurate enough for that. However, they are good enough for telling when caps are good or not.

In the case of a cap starting to show just slightly higher ESR, but still nothing too crazy - the circuit probably won't malfunction because of that. Usually it can take for the ESR to increase from 20x to 100x the nominal value before issues are anywhere close to cropping up.

That aside, those testers can be useful for telling when a cap is about to fail sometimes. Particularly, if you see the capacitance of a cap reading over 20% of the printed value on the sleeve, consider it suspect and likely to fail in the future. Caps that read grossly over 20% of their nominal stated capacitance are usually starting to fail with high leakage current and will only get worse over time until they short-circuit or open-circuit internally.

[spiros.p]

Re: 0 Ohm ESR ?? - Testing cap in PSU

ok i own one of these crap cheap meters and allways the readings is higher than normal.but my extech lcr200 reading no esr on these caps only lower value mf.i check other capacitors i get measurements from their esr.what is wrong?is the caps so bad that no esr sean on meter?

[momaka]

Re: 0 Ohm ESR ?? - Testing cap in PSU

i check other capacitors i get measurements from their esr.what is wrong?is the caps so bad that no esr sean on meter?

I don't know, but like I said, mine does that too with the ESR. Usually anything over 470 to 1000 uF and labeled low ESR will typically read 0 Ohms ESR. In fact, today I was trying to check the resistance of a 0.035 Ohm resistor and it still showed 0.00 Ohms. I've also calibrated my meter like a 100 times already. A few months ago, it started doing this thing, that after using it for a while (like after checking 10-20 components), it would say it's not calibrated. I'd then have to calibrate it (to get rid of the stupid message! ) and all would be fine again for a while. But regardless if I just calibrated it or if it says it's not calibrated, it still measures capacitors the same way... and always has ever since I bought it.

So IDK what the heck goes wrong with these... but I will never trust them 100% - ever. These meters are only good enough for checking if a cap really is bad or not - as in, grossly over normal ESR or capacitance too low or too high. And I don't even bother to look at the Vloss measurement on cap values. Seems that it's mostly "OK" (regularly measuring below 5%)... but sometimes it doesn't and I'm pretty sure the cap is OK.

[PanicMechanic]

Re: 0 Ohm ESR ?? - Testing cap in PSU

I don't know which LCR or just ESR meter you have, maybe it is showing OL (overload, out of range, or something), not 0 ohms.

But I would just get a proper LCR meter. I have a DER EE DE-5000 LCR meter. Stupid name, but amazing specs for the price. At least when I got it, maybe LCR meters have dropped in price since then.

https://www.deree.com.tw/de-5000-lcr-meter.html

[momaka]

Re: 0 Ohm ESR ?? - Testing cap in PSU

I don't know which LCR or just ESR meter you have, maybe it is showing OL (overload, out of range, or something), not 0 ohms.

It's those cheap multi-component GM328 -based testers found on eBay, AliExpress, Amazon... and really just about anywhere online. They are really more of a hobby-grade tool than a professional one, but they do work "OK" for the most part.

These don't show "OL" or out-of-range. Since they are multi-component testers, they try to identify the component automatically, and then check the specs. If the component cannot be identified (due to being bad or just not fully connected to the meter), then the meter will usually say "no, unknown, or bad part". So the ESR reading 0 Ohms on these is indeed 0 Ohms, as far as the meter is concerned. Now, that may not (and probably very likely it isn't) an accurate measurement. If anything, it's more likely the ESR is lower than what the meter can measure and/or right on the bottom end of what the meter could measure + slightly inaccurate calibration causing the meter to read lower than actual component value. In any case, I don't think anyone should expect amazing accuracy out of these cheap testers. Some might be able to do it, but some might not. I know mine cannot (or at least with its current firmware), so I just use the results it gives me as a close approximation of the real component values.

But I would just get a proper LCR meter.

Well, that all depends on every person's use. For hobby use or infrequent repairs, it may not be worthwhile to get a proper LCR meter, even if it will likely give more consistent results. The cheap GM328 testers are usually just "good enough". So you pretty much get what you pay for in that regard.

I think mine cost $13 or less back in 2013 (or was it 2014/2015? I don't remember exactly) when I got it - that's including shipping to my door. I've used it quite a bit, and it has allowed me to find many bad caps. It does have its flaws and quirks... but even with those, it's been a useful tool. So I can't really complain, given the price.

Obviously a proper LCR meter like yours would have many other benefits, particularly for testing caps and inductors/transformers. But again, for hobby use or even semi-professional use/repairs, a cheap ESR meter is often an acceptable compromise.

[kaypdss]

Hello for everyone.. i will add something that happened today while repairing a ATX Power Supply
I detected a shortcut on the -12V line to ground.
I removed the electrolictic capacitor of that line (1000uf 16V) and measure it with my capa check, it showed 980uf, but .00 ESR. So i was happy with an ideal of 0 ESR... i keep looking anothers things and cant found any other defect, so i switched the mentioned capacitor for another one previously used, 970us 0.13 ESR and the power supply started OK and no shorcut on that output.. but if i check continuity with the multimeter on that 0 ESR capacitor doesnt have a full shorcut.. but yes when it was soldered on the PS.
I can't explain but sharing the experience.. if you have an 0 ESR Capacitor.. better replace it.