Capacitors leaking on LG 50PC3D

It was certified by all my warranty work requirements. Teac/Tascam, Panasonic, Sansui, Yamaha, Sony etc...

Why would an 'audio generator' need to have a resolution up to 1 Mhz?

That's nice but I use a signal/function generator to generate signals out of the audio realm.

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My Leader LFG-1300S goes to 2MHz. My broken Wavetek Model 120 also goes to 2Mhz. My broken HP 3312A function generator would go to 13Mhz if it would kindly allow itself to be fixed. The square waves start to have rounded corners near the higher frequencies, but at 100Khz, it's a real nice square wave.

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Thanks for the clarification. I suspected something like that, but didn't consider the cable's self-inductance would be significant at 100kHz.

In other words... If the driving frequency is high enough that the capacitive reactance is essentially zero, then the net impedance is essentially the ESR. Right?

"William Sommerwerck"

** Errr - yep.

But it ain't that simple.

One has to examine the actual impedance curves for typical electros to see what the game is - the curve is like no other kind of cap.

Think of Q factors of circa 0.05 and ESRs that way exceed the calculated impedance at 100kHz.

..... Phil

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Nice tip thanks Phil. The 100uF electro's I have came out with ~0.15 ohms of ESR, using your method. I've never seen an impedance curve for an electro cap. Do you have a link or know which manufacturer's website I might check?

As a 'silly' rule of thumb it seems that most caps I run across have a minimum impedance of ~0.1 ohms. (Ignoring the 'resonant' dips that you sometimes see in the impedance plot.)

George H.

snipped-for-privacy@yahoo.com Inscribed thus:

Since Phil is comparing impedance values and not component values, I guess Phil is right !

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Nice tip thanks Phil. The 100uF electro's I have came out with ~0.15 ohms of ESR, using your method. I've never seen an impedance curve for an electro cap. Do you have a link or know which manufacturer's website I might check?

** Found this PDF on the net - seems to have lots good info on the humble electro.

See page 15, figs 13 and 14.

One can easily see the dramatic effect temperature has on the impedance minima or ESR - electros work better when they are HOT !!

Also, the minimum impedance value ( same as the ESR ) occurs around 50 -

100kHz and is quite broad - the higher the ESR and the lower the temp the broader.

At 20C the 47uF, 350 volt electro in fig 14 exhibits a deep impedance minima ( essentially 0.4 ohms resistive ) from 10kHz to 2 MHz.

.... Phil

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That's great! Thanks Phil, I found some graphs by Vishay, but they weren't nearly as nice. (No temperature dependence and frequencies only to 100kHz) Of course at high temperatures the electro's leak more.

I used your techinque to look at a 1000uF cap. I used a DSO with a bit of signal averaging. ('scope triggered from a sync output from the generator) I got something like 0.016 ohms at 100kHz. Our SRS RCL meter measured 0.014 ohms at 10kHz for the same cap. and then 'lost it's mind' at 100kHz. (reported a negative capacitance.)

George H.

On 1/27/2011 7:06 AM George Herold spake thus:

Perhaps you've stumbled onto the "anti-capacitor". Maybe you could patent it ...

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ing

gn

Hmm, Well I was thinking about this. Perhaps the RCL meter looks at the phase shift to get the sign. The minus sign would indicate that at 100kHz the 1000uF cap has passed through it's minimum impedance point and is now rising up the other side and looking more inductive to the driver.

(Just a guess.) George H.