ESR

Normally, a lower ESR is better. There is no magic number for what “correct” ESR is because it’s a rated value for them. The value should be less than a kΩ, and depending on the quality of the capacitor should probably be less than 100Ω. Identifying the type of capacitor and finding new examples with similar ratings online to compare to will be a helpful option here. Looking at similar capacitors from DigiKey, Mouser, etc and seeing what values the manufacturers rate them for can give you an idea of what “normal” is.

Here we take a look at the various and curious ways we can use an ESR Meter! Learn how to test and recognise bad capacitors, test and measure unknown inductors and even trace short circuit MOSFETS using an ESR meter

CHAPTERS
00:00:00 Intro
00:00:47 What Is ESR
00:05:06 Testing Capacitors
00:10:34 How Does ESR Meter Work?
00:12:00 Bad Capacitors (type 1)
00:14:19 Bad Capacitors (type 2)
00:16:56 Measuring Inductors
00:30:39 Short Circuit Finding In VRM
00:38:04 That’s Not A Knife!
00:40:04 Conclusion

Additionally a new parameter is output for capacitors with more than 5000 pF and low
quality factor. This parameter is the voltage loss (Vloss) immediately after a load pulse.
Some older paper capacitors make problems to get the right capacity. The error can be
more than 100%. Also other instruments have problems to measure the right capacity for
that capacitors. For type of capacitor a voltage loss of more than 10% is measured, so the
Tester gives you a warning hint with the Vloss.

VLOSS = Initial capacitor voltage loss due to the energy required to complete the
switchover operation

Capacitor voltage loss (Vloss)
Additionally a new parameter is output for capacitors with more than 5000 pF and low
quality factor. This parameter is the voltage loss (Vloss) immediately after a load pulse.
Some older paper capacitors make problems to get the right capacity. The error can be
more than 100%. Also other instruments have problems to measure the right capacity for
that capacitors. For type of capacitor a voltage loss of more than 10% is measured, so the
Tester gives you a warning hint with the Vloss.
VLOSS = Initial capacitor voltage loss due to the energy required to complete the
switchover operation (see Figure 4).
Voltage loss after a load pulse, Vloss 1
[ With the measurement of capacitors with big capacity values the voltage loss after the
loading is analysed. The reached load voltage is lost with electrolytic capacitors after a
short periode. This voltage loss can be caused by a parallel connected resistor. But I
assume, that this voltage loss of electrolytic capacitors is caused by a internal load
dispersion directly after the load pulse. By loading the capacitors with the 470 kohm
resistor, as it is done for little capacity values, this dispersion is already done after
switching o the current. No voltage loss is detectable for this case. But if you load the
same capacitor with a short current pulse, you can also detect the voltage loss for
capacitors with lower capacity. The same e ect with lower loss can also be noticed for
ceramic type capacitors.
I have noticed, that capacitors with more than some % voltage loss are suspect. Especially
noticable with respect to the voltage loss are older paper type capacitors, which are for
other measurement a problem too.

The TransistorTester can only
determine the voltage loss, if the measured capacity is more than 5000 pF.

I have recently purchased a great little tool to help test components with. It seems to work great and automatically identifies what component you are testing and it’s values. (Probably old news to most but I’m like a kid in a candy store with it) Anyway, with regard to caps, what is an acceptable voltage loss percentage? I’m working through this old northern electric 626 and will not replace the caps if they are testing good. I realize they may act differently in circuit and functioning but for now I’ll just pop in what’s way out of whack. Thanks!

Any voltage loss % does mean the old capacitor is drying out. Does not get better and gets worse over time. Best to replace all old capacitors at the same time. Makes a dependable radio.

Unless your tester can test capacitors at their rated voltage, it won’t find the bad capacitors in your radio. The general rule is that all the paper capacitors and almost all the electrolytics are bad. If you can’t test them with high voltage applied, just replace all of them.

Paper [& electros] – particularly the higher voltage types – will [almost] always show some Vloss though, regardless of their state. You can probably figure on a couple of % or more being pretty standard for paper & electros (if you even bother to measure the latter!).

I wouldn’t be surprised if old papers are up around 5%~10% or so simply due to materials & construction, not age or service-related deterioration. It’s also something of a pointless test in many cases, since (amongst other reasons) it doesn’t scale linearly with applied voltage – a cap that tests with a 1V drop @ the 3V supplied by a simple tester will show 30% Vloss, but the same cap might only drop 4V @ its rated 400V i.e. 1% Vloss and be perfectly within specs for its type.

Vloss is the dissipation factor readout in these meters. 9% is D=0.09. Word is those testers use a 1 kHz test signal.

Those yellow axial caps that people use sometimes have a dissipation factor of <0.01, or 1% at 1 kHz.

A random high-end Kemet cap has a 0.04% dissipation factor. That'd be D=0.0004.

In general, you should replace that style of cap straight away as they're so far past their working lifetime even if you randomly happen to find one that "works" it very quickly will stop doing so…but that is a fun tester and is pretty useful in a lot of situations!