JJ capacitors high ESR?

[Axtman]

I ordered some new JJ capacitors from a reliable distributor. Before I installed them I checked them on my ESR meter (actually both meters) and they had high ESR! Has anyone had experience with these capacitors?

I also ordered some F&T capacitors and they tested just fine with low ESR.

[m1989jmp]

How high was ESR on JJ's? Also what was it on F&T's, I'm curious?

I never really tried them as they're only about 10-15% cheaper than F&T here in Europe and F&T has a long history making (only) caps.

[Axtman]

The JJ capacitors are 20uf / 500v with an ESR of 5.0 ohms.

The F&T capacitors are 220uf / 300v with an ESR of 0.15 ohms.

[The Dude]

More UF usually = lower ESR so that doesn't seem horribly unreasonable to me.

[Mick Bailey]

I just took a reading of a new JJ 500v 32uf+32uf. One section reads 7.0 Ohms and the other 7.8. Much higher than I was expecting. By contrast a few good Mallory 20uf 500v 'pulls' all read 0.6 Ohms.

A 22uf/35v cheapo Chinese axial reads 4.1 ohms.

Never had a problem with the JJs though and I don't know if the ESR drops after the capacitor has been run at operational voltage.

[alexradium]

ESR meters are ok for low voltage capacitors,you should evaluate them at working voltage,with a proper capacitor checker or simply hooking one to a HV power supply with a resistor in series to monitor charge current and compare it with datasheet.
5 ohms is a lot,it should be under 2 for that size,my F&T are around 1,5,but in preamp stages its not that critical cause current is very low,it can be a problem if you intend to use them in the power stage of a 20 watt deluxe.

[1ampman]

I've used a lot of JJ 500V can caps for tube stereo gear and never had a problem. Also I don't measure caps & don't have an ESR meter. Interesting find & not sure it makes any difference. The only caps I don't like are Illinoise

[m1989jmp]

The JJ capacitors are 20uf / 500v with an ESR of 5.0 ohms.

The F&T capacitors are 220uf / 300v with an ESR of 0.15 ohms.

That's waaaay off according to some ESR charts.

Yesterday I measured a cheapo 1uF 16V e-cap, ESR = 0.7 ohms.

F&T is around for 60+ years in the cap business, there is no reason to use JJ caps.

I know on some webshops the price is almost 3:1, but F&T can caps can be purchased for a bit more than JJ's if you know where to search.

Of course, maybe you just got a bad one...

[Mick Bailey]

High ESR really becomes an issue with pulsed applications where the cap is subjected to high current draw and needs to recharge quickly for the next pulse. This is why SMPS caps are often specifically rated for low ESR. Tube amps can get away with relatively high ESR and not be a problem. I disagree with Alexradium; I use an ESR meter all the time on high voltage caps and wouldn't be without it. It's a really good indicator a of a failing cap - sometimes even before there are any symptoms. A cap that has (say) an ESR of 30 ohms where the other identical caps read maybe 4 ohms is never a good cap, but there may be no obvious deterioration noticed by the customer. Fender Hotrod and Deville series amps are always a good contender for one or more caps going high before they eventually give trouble. Obviously a shorted cap will read low ESR, and a leaking cap won't necessarily give a high reading. But I can say that like tube testers, and ESR meter will tel you a component is bad but not necessarily that its good.

[MarkusBass]

I just took a reading of a new JJ 500v 32uf+32uf. One section reads 7.0 Ohms and the other 7.8. Much higher than I was expecting. By contrast a few good Mallory 20uf 500v 'pulls' all read 0.6 Ohms.
A 22uf/35v cheapo Chinese axial reads 4.1 ohms.
Never had a problem with the JJs though and I don't know if the ESR drops after the capacitor has been run at operational voltage.

I think that there is nothing wrong with JJ capacitors. Rather, the measurement method is slightly incorrect. First, the datasheet says: "after 5 minutes application of rated voltage". But apart from this, none of you has specified the frequency of the signal used for the measurement. Usually, every DSR/capacitance meter has variable frequency for the measurement. Of course, different frequencies should be used for different capacitances. It's hard to imagine that you would expect correct results measuring 100pF with 100Hz signal. Also, it is difficult to imagine that someone expects good results for 22uF capacitor with 100kHz signal. It means that every meter has a possibility to adjust the signal frequency to the capacitance of the measured capacitor. The meter that I have allows for adjusting the frequency from 100Hz to 100kHz (in x10 steps). And I measured several JJ capacitors that I have (30uf/500V) and without applying rated voltage for 5 minutes I get 0.062 Ohm at 100Hz. And the capacitance is 28.9uF. Of course, if I switch the measurement frequency to e.g. 100kHz, I get 4.3 Ohms but also 3.5uF capacitance which obviously is incorrect. It means that capacitors in range 10-100uF cannot be measured with 10kHz, or 100kHz signal.
I compared the results with F&T capacitors (22uF) and I get 0.07 Ohm.
So there is nothing wrong with the capacitors but rather the meter is not set up correctly. Please, check whether you can alter the measurement frequency with your meter. If not, you have to change the meter.
BTW, I use EXTECH LCR200, which I assume is an american product and it's very precise when used properly.

Mark

[nsubulysses]

It might be good to buy JJ capacitors just to keep them in business so they can keep making the tubes you need. Other than that I usually choose United Chemi-con, Nichicon. And F&T occasionally if I want to be "traditional"

[Enzo]

And if we didn't have an ESR meter, we would have installed those JJ caps, the circuit would have worked anyway, and we would never have know there was a "problem".

[mozz]

And if we didn't have an ESR meter, we would have installed those JJ caps, the circuit would have worked anyway, and we would never have know there was a "problem".

But you have the $300 wire stripper?

[Enzo]

Nah, $100 stripper.

I am very skilled with the cheap little stamped flat ones too, but the pro strippers are so much more efficient and work so well, they add to my work quality and efficiency. I didn't buy the expensive stripper and find out I would HAVE to use it on everything I stripped.


Give a guy a thermal sensor, and next thing you know he is checking the temperatures of the tubes, the transformers, the resistors, the caps, the god knows what. And asking if they are OK???

[nevetslab]

If you have access to a network analyzer, or even a spectrum analyzer, you can set that up to sweep the relative impedance of the capacitor(s) over a wide frequency range. With Electrolytic's, they will decrease in capacitive reactance linearly until they begin to approach the ESR limits, and then you'll see the impedance take an upwards turn as they become inductive. There's a good discussion in the Nichicon Tech Notes for Aluminum Electrolytic capacitors,http://music-electronics-forum.com/i...attach/pdf.gif which I've attached. See Section 1.6[ATTACH]45746[