How to transcribe loss factor in Z ???

[diyiggy]

Hi,

Noob question I have, about loss factor understanding please.

How to translate the loss factor of a lytic cap in term of R value ???

For instance, a lytic cap with a loss factor of 0.6 % at 1K Hz: what does it give in serie reistance please if I had for instance to swap it with a teflon or a styren with 0.0001 loss factor and ad a resistor to cope with the old ESR of the lytic cap ????

Or is it simply impossible to do ?

 

[MarcelvdG]

The effective series resistance is roughly (or maybe even exactly) the loss factor times the reactance, so for a loss factor tan(delta) that would be tan(delta)/(2 pi f C).

In many cases the ESR is undesired, so there would be no need to add resistance. The are exceptions, for example output decoupling of old voltage regulator ICs, they would become less stable without ESR.

 

[Lojzek]

What is the point in exchanging a npe capacitor with a higher quality film cap and then ruin it with a series resistor to make it look again as npe? Instead, exchange a npe with another new npe.

0.6% means the ESR of the cap equals 0.6% of the capacitive reactance at specifed frequency of the cap you are considering. Look up for the right triangle loss tangent explanation to learn more. You can also search for capacitive reactance formula.

 

[diyiggy]

I'm going to do the math according your answers to understand more.

The question is strange indeed, but it is about old speakers refurbishing when the filters were made full lytics and the ESR a part of the design for the best designers when they used to calculate the serie resistance of those filters for medium and treble section... often second order max 40 or 50 years ago.... ad sometimes not so long ago !

I was theorically asking myself if the worst ennemy is the high ESR of lytics or the behavior of resistors (even the best double wounded or bulk ones from todays)...

Many thanks for these answers guys, exactly what I was looking for

 

[diyiggy]

.... I measured the capacitance of some of the filter NPE...some drifted towards higher values up to 15% sometimes... my tool is basic and I don't know if one need to check the capacitance of a npe with impules at a given frequency ? (1 K Hz being the most used both for film an lytics ?
My basic 20 euros tool is setuped with a 10 pF 1% military film cap....

Well I assume a good reason to go towards soundcard and a good soft to measure serie filter caps capacitance.... as I can not believe that a capacitance of a 40 years old npe can increase

Lol, I was not aware that caps measurement in speakers was so tricky... also I assume esr of a film cap given at 10 kHz by the manufactur is not saying much for a mid crossover at 200 Hz for instance ?!

I would hope that sites like Troelgravsens or Humblehomemadehifi or Jon L for the most famous give their measurement chart when it coles to caps checking...if any.

 

[Lojzek]

There is no mistery to be discovered. NPE can be of higher values when new than specified.
You do not need any obscure sites to tell you what a capacitor can do. Learn to measure impedance, it will tell you all you need to know.

 

[diyiggy]

For me it's a mystery a npe rated at 5% is 15% higher after 40 years than its marked body initial value... if 15% instead 5%, the value should have lowered after 40 years use no ? Was it 25 % instead 5%??? (these caps are in serie with the drivers, not mearasured the others yet, still have to reove these last from the board.)

I assume it's because of the drifting in frequency due to dry electrolyt ?