Power transistor question...

"Jeff Liebermann"
"Phil Allison"
That link shows ESR curves with frequency of a couple of * CERAMIC *
capacitors of unusually high values.

Oops, y'er right. Sorry(tm).

Oddly, while the ESR of the ceramic caps are much lower than
electrolytics, the curve shapes seem to be similar.

Googling, I find:
http://www.low-esr.com/esrfreqperfcurves.asp
Note the dip in ESR and loss tangent at around 100KHz on various
graphs.

** I see no such trend for the electros.

The ESR of most electros is almost constant down to about 500Hz, then rises
to a few times its high frequency value at 50Hz. I believe mobility of the
ions in the electrolyte is the cause.

Electros uniquely have very low Q factors - which means their impedance *
stays low * over a very wide frequency range.

A typical 470uF electro has an impedance under 0.1 ohms from 4kHz to 1MHz as
does the 330uF example in the graphs.

High Q capacitors ( film and ceramic) all have sharp impedance dips at self
resonance.


..... Phil
 
"Phil Allison" <phil_a@tpg.com.au> wrote in message
news:94j1ebFms1U1@mid.individual.net...
"Meat Plow"

http://www.youtube.com/watch?v=zEA5MfllPdg

Not a bad little meter for the $$$$. Anyone who does work on consumer
electronics ought to have one or something similar. Removes a lot of
guess work.


** I disagree.

An LCR meter is more useful for design and production than in servicing.

Many low cost DMMs include capacitance ranges that can measure from a few
pF up to 200 or 2000uF.

A dedicated ESR meter handles electros just fine while in circuit - and
lets you test all kinds of cells too, which an LCR meter often cannot.

Any DMM can read the resistance of an inductor or transformer winding.

The only function left is to measure inductors for value.


.... Phil
Wanted to thank *everyone* for the info and encouragement I have received in
this discussion. Bottom line for me, at least for now, is simply don't test
in-circuit (pop one lead and then test after discharging). Have also found
a ton of material on youtube and the net that convinces me to get a
dedicated ESR meter (or possibly build one.) Anyway, thanks all for a very
enlightening discussion.

Take it easy...

Dave
 
"Dave"
Wanted to thank *everyone* for the info and encouragement I have received
in this discussion. Bottom line for me, at least for now, is simply don't
test in-circuit (pop one lead and then test after discharging). Have also
found a ton of material on youtube and the net that convinces me to get a
dedicated ESR meter (or possibly build one.) Anyway, thanks all for a
very enlightening discussion.

** This is the one I would buy - if I did not already have two of Bob's
earlier designs.

http://www.anatekcorp.com/blueesr.htm

BTW

Bob is an old mate of mine.



..... Phil
 
Dave wrote:

"Phil Allison" <phil_a@tpg.com.au> wrote in message
news:94j1ebFms1U1@mid.individual.net...

"Meat Plow"


http://www.youtube.com/watch?v=zEA5MfllPdg

Not a bad little meter for the $$$$. Anyone who does work on consumer
electronics ought to have one or something similar. Removes a lot of
guess work.


** I disagree.

An LCR meter is more useful for design and production than in servicing.

Many low cost DMMs include capacitance ranges that can measure from a few
pF up to 200 or 2000uF.

A dedicated ESR meter handles electros just fine while in circuit - and
lets you test all kinds of cells too, which an LCR meter often cannot.

Any DMM can read the resistance of an inductor or transformer winding.

The only function left is to measure inductors for value.


.... Phil



Wanted to thank *everyone* for the info and encouragement I have received in
this discussion. Bottom line for me, at least for now, is simply don't test
in-circuit (pop one lead and then test after discharging). Have also found
a ton of material on youtube and the net that convinces me to get a
dedicated ESR meter (or possibly build one.) Anyway, thanks all for a very
enlightening discussion.

Take it easy...

Dave


I use a cheap B&K LCR, it does in circuit beautifully.

Jamie
 
On Tue, 31 May 2011 12:17:38 +1000, Phil Allison wrote:

"Meat Plow"

http://www.youtube.com/watch?v=zEA5MfllPdg

Not a bad little meter for the $$$$. Anyone who does work on consumer
electronics ought to have one or something similar. Removes a lot of
guess work.


** I disagree.

An LCR meter is more useful for design and production than in servicing.

Many low cost DMMs include capacitance ranges that can measure from a
few pF up to 200 or 2000uF.

A dedicated ESR meter handles electros just fine while in circuit - and
lets you test all kinds of cells too, which an LCR meter often cannot.

Any DMM can read the resistance of an inductor or transformer winding.

The only function left is to measure inductors for value.


.... Phil
I'd like to see the meter described test at a higher frequency but other
than that I can't find much else wrong. I've been relying on an old Tenma
cap meter for years. It's gets you in the ball park. And there were
reliable repairs before LCR and ESR meters. I know, been at it from high
school back in 1970. These days I tend to shy away from anything I need
an ESR meter for. Plenty of vintage stuff out there that people like to
keep going.



--
Live Fast Die Young, Leave A Pretty Corpse
 
"Meat Plow"
I'd like to see the meter described test at a higher frequency but other
than that I can't find much else wrong. I've been relying on an old Tenma
cap meter for years. It's gets you in the ball park. And there were
reliable repairs before LCR and ESR meters. I know, been at it from high
school back in 1970. These days I tend to shy away from anything I need
an ESR meter for. Plenty of vintage stuff out there that people like to
keep going.

** ESR meters are MOST useful with older equipment, particularly valve
amplifiers.

All those electros are old and have been running in a hot environment.


...... Phil
 
"Jamie" <jamie_ka1lpa_not_valid_after_ka1lpa_@charter.net> wrote in message
news:QVdFp.9148$rq2.7889@newsfe12.iad...
Dave wrote:

"Phil Allison" <phil_a@tpg.com.au> wrote in message
news:94j1ebFms1U1@mid.individual.net...

"Meat Plow"


http://www.youtube.com/watch?v=zEA5MfllPdg

Not a bad little meter for the $$$$. Anyone who does work on consumer
electronics ought to have one or something similar. Removes a lot of
guess work.


** I disagree.

An LCR meter is more useful for design and production than in servicing.

Many low cost DMMs include capacitance ranges that can measure from a few
pF up to 200 or 2000uF.

A dedicated ESR meter handles electros just fine while in circuit - and
lets you test all kinds of cells too, which an LCR meter often cannot.

Any DMM can read the resistance of an inductor or transformer winding.

The only function left is to measure inductors for value.


.... Phil



Wanted to thank *everyone* for the info and encouragement I have received
in this discussion. Bottom line for me, at least for now, is simply
don't test in-circuit (pop one lead and then test after discharging).
Have also found a ton of material on youtube and the net that convinces
me to get a dedicated ESR meter (or possibly build one.) Anyway, thanks
all for a very enlightening discussion.

Take it easy...

Dave


I use a cheap B&K LCR, it does in circuit beautifully.

Jamie
Hey Jamie, thanks for the note. So, how do you perform an in-circuit ESR
test on a suspect cap? Do you bother to discharge it, or do you just let
the circuitry around the cap do that? And how reliable are the numbers you
come up with? I tried to do an in-circuit test today on a cap and thought I
had gotten lucky with my first shot. A 10uF @ 100V cap gave me an ESR
reading of 42.15 in-circuit, but when I popped it out and tested it again it
dropped to 0.12. big difference! Still trying to figure out what I might
have been doing wrong...

Have since discovered a different cap that may actually be the problem. A
..22uF @ 50V cap with an ESR reading of 25+ ohms. Am thinking this component
may be where the vertical hold sync pulse gets lost, as it feeds an
oscillator/mixer transistor which feeds the output transistor of the
vertical hold circuitry. All of this two days after I discovered I had an
ESR meter and didn't know it. <shaking head>

Dave
 
"Dave"
"Jamie
= Maynard A. Philbrook
= Lunatic, code scribbler & radio ham: KA1LPA

I use a cheap B&K LCR, it does in circuit beautifully.
** Blatant lie.

Hey Jamie, thanks for the note. So, how do you perform an in-circuit ESR
test on a suspect cap?
** Jaime is a congenital bullshit artist.

Just IGNORE him.


I tried to do an in-circuit test today on a cap and thought I had gotten
lucky with my first shot. A 10uF @ 100V cap gave me an ESR reading of
42.15 in-circuit, but when I popped it out and tested it again it dropped
to 0.12. big difference! Still trying to figure out what I might have
been doing wrong...

** All that means is there is some resistance in parallel with the 10uF cap.

Any parallel resistance is computed to a misleading ESR number by an LCR
meter.

That's the problem.

With a dedicated ESR meter that measures the impedance of an electro at
100kHz, the effect of parallel resistors or diode junctions that may exist
is ignored.



..... Phil
 

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