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Caps in amps

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Anonymous
August 20, 2004 7:29:12 AM

Archived from groups: rec.audio.pro (More info?)

Someone (Scott?) suggested in another thread to replace the caps in 30 year
old amps. I have one, so I went googling for info on my Phase Linear 700
Series II, about 30 years old but still sounding fine.

Is what this guy says correct? As long as it sounds good it's OK?

This is from a Phase Linear site:

Q: I've heard that all electrolytic capacitors in the power amplifiers
should be replaced with new ones. Is this correct?

A: First and foremost, as with other modern amps, all Phase Linear power
amps are direct coupled and have NO electrolytic caps in the signal path.
There are elctrolytic caps in the power supply, feedback network and
bootstrap circuit, and protection circuit

* Power supply: power supply filter cap failures are rare but they do
occur. When they fail, they generally fail suddenly and there is no way to
to accurately predict when one will fail. High value electrolytic caps are
much more expensive than they used to be.
* Feedback network: all drive boards from the PL14A onward have a 100uF
cap to ground (C 6 on the PL14) in the feedback network. The purpose of
this cap is to roll off gain at subsonic frequencies. When working
correctly, gain should be down about 0.5-1 dB at 20 Hz. The only time I see
these fail is if the amp has failed and latched up (excessive DC offset).
Failures due to any other cause are nil.
* Bootstrap circuit: bootstrapping is a type of positive feedback. The
purpose of the bootstrap cap (C 11 on the PL14) is to provide symetrical
drive voltage to the positive output bank. Failure will cause asymetrical
clipping on the positive side. I think I've replaced one in the past 28
years!
* Protection circuit: this circuit only turns on when the amp is driven
into a short circuit or very low impedance. Under normal operation it is
completely out of the signal path. See C 15 and 16 on the PL 14. I've never
replaced a single one. Series 2 and 3 drive boards don't have these caps.

At this point in the life of these amps, electrolytic cap failures are
rare. However,electrolytic caps will eventually fail due to age. My advice
is to save your money and only replace them as needed. This advice may
change in another 10 or 20 years. I'll keep you posted!

http://hometown.aol.com/phasetek/faqgeneral.html

More about : caps amps

Anonymous
August 20, 2004 1:01:16 PM

Archived from groups: rec.audio.pro (More info?)

In article <Xns954AEF0617271gulfjoehotmailcom@207.69.154.203> gulfjoe@hotmail.com writes:

> At this point in the life of these amps, electrolytic cap failures are
> rare. However,electrolytic caps will eventually fail due to age. My advice
> is to save your money and only replace them as needed. This advice may
> change in another 10 or 20 years. I'll keep you posted!

I think that the author is confusing "failure" with "not the same as
it was when it was new." While aluminum electrolytics (typically
what's used as fliters in power supplies) usually need more
encouragement than age to fail in the short-circuit mode - which would
cause some other damage or at least shutdown or strain - they do
become less capacitor as the electrolyte ages.

These capacitors generally have tolerances as wide as -50%/+100% but
when a 5,000 uF filter capacitor becomes a 2,000 uF filter capacitor,
both the ripple output and transient handling capacity is less than
what the designer intended. It may still be good enough for government
work, but it's always the one with the time or money who decides
whether capacitors in an apparently working amplifier should be
replaced.

--
I'm really Mike Rivers (mrivers@d-and-d.com)
However, until the spam goes away or Hell freezes over,
lots of IP addresses are blocked from this system. If
you e-mail me and it bounces, use your secret decoder ring
and reach me here: double-m-eleven-double-zero at yahoo
Anonymous
August 20, 2004 2:00:46 PM

Archived from groups: rec.audio.pro (More info?)

Carey Carlan <gulfjoe@hotmail.com> wrote:
>Someone (Scott?) suggested in another thread to replace the caps in 30 year
>old amps. I have one, so I went googling for info on my Phase Linear 700
>Series II, about 30 years old but still sounding fine.
>
>Is what this guy says correct? As long as it sounds good it's OK?

For the most part, yeah. But measure the low end response... when it
starts dropping on the bottom end, you have a problem.

I would be a little surprised if a Phase Linear today still met the original
response specs without recapping. But if it does, don't worry about it.
--scott

--
"C'est un Nagra. C'est suisse, et tres, tres precis."
Related resources
Anonymous
August 20, 2004 5:43:39 PM

Archived from groups: rec.audio.pro (More info?)

"Carey Carlan"

> Someone (Scott?) suggested in another thread to replace the caps in 30
year
> old amps. I have one, so I went googling for info on my Phase Linear 700
> Series II, about 30 years old but still sounding fine.
>

** Series II models are about 23 years old.


> Is what this guy says correct? As long as it sounds good it's OK?
>
> This is from a Phase Linear site:
>
> Q: I've heard that all electrolytic capacitors in the power amplifiers
> should be replaced with new ones. Is this correct?
>
> A: First and foremost, as with other modern amps, all Phase Linear power
> amps are direct coupled and have NO electrolytic caps in the signal path.
> There are elctrolytic caps in the power supply, feedback network and
> bootstrap circuit, and protection circuit


** This is just plain stupid - caps used in the feedback networks and
bootstrap ARE in the signal path.

There are 100uF, 16 volt caps in the feedback that you should replace -
these are prone to drying out and losing all capacitance. Also replace the
bootstrap caps, 47 uF 100 volt for good measure.

( snip load of stuff about the WRONG model)

Also - if your PL700 mk 2 amp has two 2.4 kohms 5 watt cement resistors on
the PCB - replace them immediately with new 4.7 kohm 5 watt rated ones.

These resistors are *famous* for going open and sending both outputs to
full DC !!!




.............. Phil
Anonymous
August 21, 2004 3:17:06 AM

Archived from groups: rec.audio.pro (More info?)

"Mike Rivers"
gulfjoe@hotmail.com writes:
>
> > At this point in the life of these amps, electrolytic cap failures are
> > rare. However,electrolytic caps will eventually fail due to age. My
advice
> > is to save your money and only replace them as needed. This advice may
> > change in another 10 or 20 years. I'll keep you posted!
>
> I think that the author is confusing "failure" with "not the same as
> it was when it was new." While aluminum electrolytics (typically
> what's used as fliters in power supplies) usually need more
> encouragement than age to fail in the short-circuit mode - which would
> cause some other damage or at least shutdown or strain - they do
> become less capacitor as the electrolyte ages.
>

** I wonder where the NG Parrot got that one from ?

Same place Arny did ??




......... Phil
Anonymous
August 21, 2004 3:17:07 AM

Archived from groups: rec.audio.pro (More info?)

"Phil Allison" <philallison@tpg.com.au> wrote in message
news:2ombukFc60ehU1@uni-berlin.de
> "Mike Rivers"
> gulfjoe@hotmail.com writes:
>>
>>> At this point in the life of these amps, electrolytic cap failures
>>> are rare. However,electrolytic caps will eventually fail due to
>>> age. My advice is to save your money and only replace them as
>>> needed. This advice may change in another 10 or 20 years. I'll keep
>>> you posted!
>>
>> I think that the author is confusing "failure" with "not the same as
>> it was when it was new." While aluminum electrolytics (typically
>> what's used as fliters in power supplies) usually need more
>> encouragement than age to fail in the short-circuit mode - which
>> would cause some other damage or at least shutdown or strain - they
>> do become less capacitor as the electrolyte ages.
>>
>
> ** I wonder where the NG Parrot got that one from ?
>
> Same place Arny did ??

"Less capacitor" does not necessarily mean, or not mean, "higher ESR" It
could relate to any parameter that a capacitor has, that makes us think that
it is a capacitor. Or just one of them. Pick one!

Therefore it's very hard to say that the statement definitely right or
wrong.

One could give Mike the benefit of the doubt...
Anonymous
August 21, 2004 3:17:08 AM

Archived from groups: rec.audio.pro (More info?)

In article <BfWdnQNbP9TvYLjcRVn-gQ@comcast.com> arnyk@hotpop.com writes:

> One could give Mike the benefit of the doubt...

This is ** Phil ** who's talking. That would never happen.

--
I'm really Mike Rivers (mrivers@d-and-d.com)
However, until the spam goes away or Hell freezes over,
lots of IP addresses are blocked from this system. If
you e-mail me and it bounces, use your secret decoder ring
and reach me here: double-m-eleven-double-zero at yahoo
Anonymous
August 21, 2004 3:35:13 AM

Archived from groups: rec.audio.pro (More info?)

"Arny Krueger"
> "Phil Allison"
> > "Mike Rivers"


> >>
> >> I think that the author is confusing "failure" with "not the same as
> >> it was when it was new." While aluminum electrolytics (typically
> >> what's used as fliters in power supplies) usually need more
> >> encouragement than age to fail in the short-circuit mode - which
> >> would cause some other damage or at least shutdown or strain - they
> >> do become less capacitor as the electrolyte ages.
> >>
> >
> > ** I wonder where the NG Parrot got that one from ?
> >
> > Same place Arny did ??
>
> "Less capacitor" does not necessarily mean, or not mean, "higher ESR" It
> could relate to any parameter that a capacitor has, that makes us think
that
> it is a capacitor. Or just one of them. Pick one!
>
> Therefore it's very hard to say that the statement definitely right or
> wrong.
>
> One could give Mike the benefit of the doubt...



** Read the Parrot's subsequent para - that removes any doubt.




............ Phil
Anonymous
August 21, 2004 3:35:14 AM

Archived from groups: rec.audio.pro (More info?)

"Phil Allison" <philallison@tpg.com.au> wrote in message
news:2omd0iFc28peU1@uni-berlin.de
> "Arny Krueger"
>> "Phil Allison"
>>> "Mike Rivers"
>
>
>>>>
>>>> I think that the author is confusing "failure" with "not the same
>>>> as it was when it was new." While aluminum electrolytics (typically
>>>> what's used as fliters in power supplies) usually need more
>>>> encouragement than age to fail in the short-circuit mode - which
>>>> would cause some other damage or at least shutdown or strain - they
>>>> do become less capacitor as the electrolyte ages.
>>>>
>>>
>>> ** I wonder where the NG Parrot got that one from ?
>>>
>>> Same place Arny did ??
>>
>> "Less capacitor" does not necessarily mean, or not mean, "higher
>> ESR" It could relate to any parameter that a capacitor has, that
>> makes us think that it is a capacitor. Or just one of them. Pick one!
>>
>> Therefore it's very hard to say that the statement definitely right
>> or wrong.
>>
>> One could give Mike the benefit of the doubt...


> ** Read the Parrot's subsequent para - that removes any doubt.

He said:

These capacitors generally have tolerances as wide as -50%/+100% but
when a 5,000 uF filter capacitor becomes a 2,000 uF filter capacitor,
both the ripple output and transient handling capacity is less than
what the designer intended.

At this point he's talking about tolerances, not necessarily parts life.

In fact, it is clear that when capacitors age and degrade, ESR increase is a
clear and indisputable indicator that the capacitor is degrading. However,
without further measurements, we don't know what else is happening at the
same time. The fact that the ESR is increasing is often sufficient cause to
say that the capacitor has failed. We need not go any further to justify
replacing the part.
Anonymous
August 21, 2004 3:51:10 AM

Archived from groups: rec.audio.pro (More info?)

"Arny Krueger"
> "Phil Allison"
>>> "Mike Rivers"

> >
> >>>>
> >>>> I think that the author is confusing "failure" with "not the same
> >>>> as it was when it was new." While aluminum electrolytics (typically
> >>>> what's used as fliters in power supplies) usually need more
> >>>> encouragement than age to fail in the short-circuit mode - which
> >>>> would cause some other damage or at least shutdown or strain - they
> >>>> do become less capacitor as the electrolyte ages.
> >>>>
> >>>
> >>> ** I wonder where the NG Parrot got that one from ?
> >>>
> >>> Same place Arny did ??
> >>
> >> "Less capacitor" does not necessarily mean, or not mean, "higher
> >> ESR" It could relate to any parameter that a capacitor has, that
> >> makes us think that it is a capacitor. Or just one of them. Pick one!
> >>
> >> Therefore it's very hard to say that the statement definitely right
> >> or wrong.
> >>
> >> One could give Mike the benefit of the doubt...
>
>
> > ** Read the Parrot's subsequent para - that removes any doubt.
>
> He said:
>
> These capacitors generally have tolerances as wide as -50%/+100% but
> when a 5,000 uF filter capacitor becomes a 2,000 uF filter capacitor,
> both the ripple output and transient handling capacity is less than
> what the designer intended.
>
> At this point he's talking about tolerances, not necessarily parts life.


** No he is NOT you posturing ass.

The two paras taken together have only one meaning - "less capacitor " =
a loss of uFs.


> In fact, it is clear that when capacitors age and degrade, ESR increase is
a
> clear and indisputable indicator that the capacitor is degrading.


** Something I told you recently.

Remember the definition I gave for a cap's end of life ????



.............. Phil
Anonymous
August 21, 2004 3:51:11 AM

Archived from groups: rec.audio.pro (More info?)

"Phil Allison" <philallison@tpg.com.au> wrote in message
news:2omdufFc9mldU1@uni-berlin.de

>
>> In fact, it is clear that when capacitors age and degrade, ESR
>> increase is a clear and indisputable indicator that the capacitor is
>> degrading.

> ** Something I told you recently.

I believe this is the case.

> Remember the definition I gave for a cap's end of life ????

Absolutely. I verified it carefully with a number of relevant white papers
from electrolytic manufacturers.

Very good!
Anonymous
August 21, 2004 3:51:11 AM

Archived from groups: rec.audio.pro (More info?)

In article <2omdufFc9mldU1@uni-berlin.de> philallison@tpg.com.au writes:

> Remember the definition I gave for a cap's end of life ????

Who died and made you king of capacitors? Haven't you ever seen a
capacitor that's out of tolerance on the low side? I have. I might
even be able to find one around here that I can send you so you can
measure it yourself. And while you're at it, measure the ESR and see
if it's dead.



--
I'm really Mike Rivers (mrivers@d-and-d.com)
However, until the spam goes away or Hell freezes over,
lots of IP addresses are blocked from this system. If
you e-mail me and it bounces, use your secret decoder ring
and reach me here: double-m-eleven-double-zero at yahoo
August 21, 2004 3:51:12 AM

Archived from groups: rec.audio.pro (More info?)

Mike Rivers wrote:

> Who died and made you king of capacitors?


Well, we used to call them condensers in the old days. I don't know of any
RAP regulars more dense than Phil. Maybe, he stuck his finger in the back
of a tube amp or an old TV set without bleeding the filter caps, & the
resulting shock condensed him.
Anonymous
August 21, 2004 3:59:51 AM

Archived from groups: rec.audio.pro (More info?)

mrivers@d-and-d.com (Mike Rivers) wrote in news:znr1092999640k@trad:

> I think that the author is confusing "failure" with "not the same as
> it was when it was new." While aluminum electrolytics (typically
> what's used as fliters in power supplies) usually need more
> encouragement than age to fail in the short-circuit mode - which would
> cause some other damage or at least shutdown or strain - they do
> become less capacitor as the electrolyte ages.

What is the audible effect of aging capacitors? Should I start to hear low
level 60 Hz hum?
Anonymous
August 21, 2004 3:59:52 AM

Archived from groups: rec.audio.pro (More info?)

Carey Carlan <gulfjoe@hotmail.com> wrote:
>mrivers@d-and-d.com (Mike Rivers) wrote in news:znr1092999640k@trad:
>
>> I think that the author is confusing "failure" with "not the same as
>> it was when it was new." While aluminum electrolytics (typically
>> what's used as fliters in power supplies) usually need more
>> encouragement than age to fail in the short-circuit mode - which would
>> cause some other damage or at least shutdown or strain - they do
>> become less capacitor as the electrolyte ages.
>
>What is the audible effect of aging capacitors? Should I start to hear low
>level 60 Hz hum?

Depends on what the cap is doing. But hearing 60 Hz hum, and hearing
reduced low end response, are two good signs of a problem. Bad smells
and popping breakers also indicate big issues.
--scott

--
"C'est un Nagra. C'est suisse, et tres, tres precis."
Anonymous
August 21, 2004 4:04:09 AM

Archived from groups: rec.audio.pro (More info?)

"Phil Allison" <philallison@tpg.com.au> wrote in
news:2olabcFc2cr5U1@uni-berlin.de:

> ** Series II models are about 23 years old.

I checked. 1978. We split the difference.

> There are 100uF, 16 volt caps in the feedback that you should
> replace -
> these are prone to drying out and losing all capacitance. Also
> replace the bootstrap caps, 47 uF 100 volt for good measure.

What will I hear as these caps fade?

> Also - if your PL700 mk 2 amp has two 2.4 kohms 5 watt cement
> resistors on
> the PCB - replace them immediately with new 4.7 kohm 5 watt rated
> ones.
>
> These resistors are *famous* for going open and sending both outputs
> to
> full DC !!!

Why from 2.4K to 4.7K?
Anonymous
August 21, 2004 4:16:04 AM

Archived from groups: rec.audio.pro (More info?)

kludge@panix.com (Scott Dorsey) wrote in
news:cg506e$jlk$1@panix2.panix.com:

> For the most part, yeah. But measure the low end response... when it
> starts dropping on the bottom end, you have a problem.
>
> I would be a little surprised if a Phase Linear today still met the
> original response specs without recapping. But if it does, don't
> worry about it. --scott

I assume most of the ill effects are from aging. Does usage have anything
to do with it? This amp is not used daily and is very seldom pushed to its
limits.
Anonymous
August 21, 2004 5:40:39 AM

Archived from groups: rec.audio.pro (More info?)

"Mike Rivers" <mrivers@d-and-d.com> wrote in message
news:znr1093020650k@trad
> In article <2omdufFc9mldU1@uni-berlin.de> philallison@tpg.com.au
> writes:
>
>> Remember the definition I gave for a cap's end of life ????
>
> Who died and made you king of capacitors?

Ahem, I studied this at length and found that ESR is THE standard
measurement for evaluating the life of capacitors, these days. Given that
ESR testers go back to the vacuum tube days, it looks like this is nothing
new!

>Haven't you ever seen a
> capacitor that's out of tolerance on the low side? I have.

I have too, and in another post I provided evidence from one of Phil's own
posts that he has seem this, too.

Since ESR is so widely used as *the* criteria for end-of-life I thought
that somewhere I'd find a chart of capacitance versus ESR, but no dice. On
balance, capacitance seems like a poor parameter to track, because initial
capacitance can vary so much.

> I might even be able to find one around here that I can send you so you
> can
> measure it yourself. And while you're at it, measure the ESR and see if
> it's dead.

It's possible that virtually every cap that has loss significant amounts of
capacitance, also has ESR problems.
Anonymous
August 21, 2004 5:41:37 AM

Archived from groups: rec.audio.pro (More info?)

"Carey Carlan" <gulfjoe@hotmail.com> wrote in message
news:Xns954BCB89133BBgulfjoehotmailcom@207.69.154.202
> mrivers@d-and-d.com (Mike Rivers) wrote in news:znr1092999640k@trad:
>
>> I think that the author is confusing "failure" with "not the same as
>> it was when it was new." While aluminum electrolytics (typically
>> what's used as fliters in power supplies) usually need more
>> encouragement than age to fail in the short-circuit mode - which
>> would cause some other damage or at least shutdown or strain - they
>> do become less capacitor as the electrolyte ages.
>
> What is the audible effect of aging capacitors? Should I start to
> hear low level 60 Hz hum?

Very possible. Also 120, 50 or 100 Hz hum depending where the capacitor is.

Two ways to get there- ESR increase and loss of capacitance.
Anonymous
August 21, 2004 10:11:22 AM

Archived from groups: rec.audio.pro (More info?)

In article <Xns954BCB89133BBgulfjoehotmailcom@207.69.154.202> gulfjoe@hotmail.com writes:

> What is the audible effect of aging capacitors? Should I start to hear low
> level 60 Hz hum?

If it's a power supply filter that isn't filtering like it should,
yes. Actually, you'll most likely hear 120 Hz hum because just about
every power supply uses a full wave rectifier.



--
I'm really Mike Rivers (mrivers@d-and-d.com)
However, until the spam goes away or Hell freezes over,
lots of IP addresses are blocked from this system. If
you e-mail me and it bounces, use your secret decoder ring
and reach me here: double-m-eleven-double-zero at yahoo
Anonymous
August 21, 2004 11:56:11 AM

Archived from groups: rec.audio.pro (More info?)

Carey Carlan wrote:

> kludge@panix.com (Scott Dorsey) wrote in
> news:cg506e$jlk$1@panix2.panix.com:
>
> > For the most part, yeah. But measure the low end response... when it
> > starts dropping on the bottom end, you have a problem.
> >
> > I would be a little surprised if a Phase Linear today still met the
> > original response specs without recapping. But if it does, don't
> > worry about it. --scott
>
> I assume most of the ill effects are from aging. Does usage have anything
> to do with it?

For psu caps certainly. Running psu caps at high ripple currents causes them to
run hot which in time 'ages' them.

All capacitors are specced for X thousand hours life at a specified ripple
current ( related to load current ) and ambient temperature. X depends on the
quality of the component.

Reduce the ripple current, or ambient temperature and the life is increased.

> This amp is not used daily and is very seldom pushed to its
> limits.

Less of an issue perhaps in that case.


Graham
Anonymous
August 21, 2004 1:58:03 PM

Archived from groups: rec.audio.pro (More info?)

Arny Krueger <arnyk@hotpop.com> wrote:
>
>Since ESR is so widely used as *the* criteria for end-of-life I thought
>that somewhere I'd find a chart of capacitance versus ESR, but no dice. On
>balance, capacitance seems like a poor parameter to track, because initial
>capacitance can vary so much.

Both the Heathkit and the little kit ESR meter that Dick Smith sells come
with charts that list minimal acceptable ESR for a given capacitance and
voltage value. But it's really just a ballpark value, since capacitors
all started out with very different ESR when they were new (compare a 1950's
Mallory with a modern Panasonic FC, for instance). Can you really use
the same standard on all of them? If your standard is too tight, you will
be swapping those old 1950s Mallorys out even though they meet original
specs. If your standard is too loose, you may miss some Panasonic FCs that
are on their way to failing.

>It's possible that virtually every cap that has loss significant amounts of
>capacitance, also has ESR problems.

Yes, they go hand in hand. But ESR is a lot easier to measure in-circuit.
--scott
--
"C'est un Nagra. C'est suisse, et tres, tres precis."
Anonymous
August 21, 2004 2:08:54 PM

Archived from groups: rec.audio.pro (More info?)

In article <p5ednUH06ZnXfbvcRVn-ow@comcast.com> arnyk@hotpop.com writes:

> Ahem, I studied this at length and found that ESR is THE standard
> measurement for evaluating the life of capacitors, these days. Given that
> ESR testers go back to the vacuum tube days, it looks like this is nothing
> new!

Can you point me to a good piece of reading matter on the subject,
particularly relating ESR to failure modes? I thought I had a general
idea of what ESR is and that it's desirable that a capacitor be
designed and built so that it is as low as possible. From the bit of
reading I've done, my sense is that this is a calculated value rather
than one that's directly measured, and that what's measured is
actually leakage (as well, of course, as capacitance) when evaluating
the design and health of a capacitor.

I wouldn't be surprised if one reason, perhaps the primary reason, for
rising ESR over the life of a capacitor is deterioration of the
electrolyte or deterioration of the plates, either of which could
cause a reduction in capacitance. While ESR might be a good production
line QA tool, if you wanted to know if a capacitor was still
functional in situ, wouldn't it make more sense to measure the leakage
(if its function is isolation) and capacitance (if its function is to
create a frequency-dependent circuit)?

I don't have to know why a power supply filter capacitor marked
5,000 uF is, 27 years later, only 2,000 uF, but if it is, I can
predict that there will be more ripple coming out of the power supply
than the designer originally intended to live with. Therefore, the
capacitor should be replaced.

Similarly, if a 100 uF coupling capacitor is now 5 uF, I can expect
that unless the value was much greater than required by the design,
low frequency response will be affected and the capacitor should be
replaced.

If, with or without a change in capacitance, the ESR has risen so that
it acts like a resistor in series with the capacitor, I could also
predict a change in frequency response. If the actual leakage has
increased so that DC can flow through the capacitor, I could expect a
bias problem if it was a coupling capacitor or a fuse blowing if it
was a power supply filter.

With all of those good diagnostic tools available, why worry about
ESR? What else is there that a capacitor should do that would be
predicted by an ESR measurement and not be apparent by some other
bench diagnostic means?

I'm talking low frequencies here, of course, and I recognize that even
in audio circuits, performance outside the audio band is important, so
I won't say I have the complete picture here, I just don't know what
else I'm missing that I might care about.

> Since ESR is so widely used as *the* criteria for end-of-life I thought
> that somewhere I'd find a chart of capacitance versus ESR, but no dice.

I wouldn't expect them to be directly related, other than perhaps for
a specific capacitor construction and value.

> On
> balance, capacitance seems like a poor parameter to track, because initial
> capacitance can vary so much.

That's why designers pay attention to tolerances put on the capacitors
by their manufacturers. It's also why electrolytic capacitors, which
generally have pretty wild tolerance, aren't used for precision
frequency determining components. So it's reasonable to design based
on the low end of the tolerance and say that when the capacitor no
longer meets that tolerance (for whatever reason), it's time to
replace it.

> It's possible that virtually every cap that has loss significant amounts of
> capacitance, also has ESR problems.

If ESR manifests itself in the functional world as I think it does,
the same thing that causes loss of capacitance is likely to cause a
change in ESR. However, there may be applications for capacitors where
ESR is not all that important as long as capacitance doesn't change
along with it.

Bottom line - I think I can tell whether a capacitor is doing what
it's supposed to do in the circuit in which it's installed without
knowing anything about ESR. If I was designing a circuit, I might want
to know about the ESR of the capacitor I intend to use becuase there
may be advantages to choosing a capacitor with a low-ESR design.
(Since this seems to be an advertised feature, I assume it increases
cost, if for no other reason than to cover the cost of documentation
and advertising.) Or it may be that for the function I intend for that
capacitor, ESR (particularly over the product's expected lifetime) may
not matter a bit, so I can make my marketing department happier by
choosing a cheaper component.

Let's not confuse theory of capacitor design with practical circuit
design or bench troubleshooting.


--
I'm really Mike Rivers (mrivers@d-and-d.com)
However, until the spam goes away or Hell freezes over,
lots of IP addresses are blocked from this system. If
you e-mail me and it bounces, use your secret decoder ring
and reach me here: double-m-eleven-double-zero at yahoo
Anonymous
August 21, 2004 2:43:56 PM

Archived from groups: rec.audio.pro (More info?)

"Carey Carlan"
> "Phil Allison" <
>
> > ** Series II models are about 23 years old.
>
> I checked. 1978. We split the difference.
>

** Then it is one of the very first series 2s.



> > There are 100uF, 16 volt caps in the feedback that you should
> > replace -
> these are prone to drying out and losing all capacitance. Also
> > replace the bootstrap caps, 47 uF 100 volt for good measure.
>
> What will I hear as these caps fade?
>

** Loss of lows, distortion, loss of volume.

Replace them now - don't wait for symptoms.



> > Also - if your PL700 mk 2 amp has two 2.4 kohms 5 watt cement
> > resistors on
> > the PCB - replace them immediately with new 4.7 kohm 5 watt rated
> > ones.
> >
> > These resistors are *famous* for going open and sending both outputs
> > to
> > full DC !!!
>
> Why from 2.4K to 4.7K?



** The lower value runs very hot and overheats the associated zener
diodes too - which can fail and send both channels DC. 4.7 kohms works
just fine.




.............. Phil
Anonymous
August 21, 2004 2:43:57 PM

Archived from groups: rec.audio.pro (More info?)

Phil Allison <philallison@tpg.com.au> wrote:
>>
>> What will I hear as these caps fade?
>>
>
> ** Loss of lows, distortion, loss of volume.
>
> Replace them now - don't wait for symptoms.

Wait a minute there, Phil. Aren't you the same guy who posted this?

Phil Allison <philallison@tpg.com.au> wrote:
> Kludge wrote:
> > On typical pro audio gear, you may see a piece of equipment recapped three
> or four times over a 30-year lifespan.
>
> ** Not on the planet most people inhabit. Must be some idiot Yank idea to
> re-cap everything - the guitar amp loonies are always on about it as some
> sort of panacea.

I see a discrepancy here.
--scott

--
"C'est un Nagra. C'est suisse, et tres, tres precis."
Anonymous
August 21, 2004 2:43:57 PM

Archived from groups: rec.audio.pro (More info?)

"Phil Allison" <philallison@tpg.com.au> wrote in message
news:2onk6dFcpi62U1@uni-berlin.de
> "Carey Carlan"

>> "Phil Allison" <
>
>>> There are 100uF, 16 volt caps in the feedback that you should
>>> replace -

>> these are prone to drying out and losing all capacitance. Also
>>> replace the bootstrap caps, 47 uF 100 volt for good measure.

>> What will I hear as these caps fade?

> ** Loss of lows, distortion, loss of volume.

Let's go down Phil's list of symptoms and assign probable causes:

Loss of lows - the cause must be partial loss of capacitance, as complete
loss of capacitance would turn the amp into a unity gain amp.

Distortion - could be leakage or increase of ESR, if nonlinear.

Loss of volume - if it is truely just a loss of volume (flat frequency
response), this is the only symptom that corresponds to a complete loss of
capacitance, See former comments about unity gain.
Anonymous
August 21, 2004 2:47:13 PM

Archived from groups: rec.audio.pro (More info?)

"Mike Rivers"
>
>Phil Allison
>
> > Remember the definition I gave for a cap's end of life ????
>
> Who died and made you king of capacitors?


** I gave the definition that all electro cap makers use - dickhead.


> Haven't you ever seen a
> capacitor that's out of tolerance on the low side?


** The ESR always goes high prior to loss of uFs.




............... Phil
Anonymous
August 21, 2004 2:47:14 PM

Archived from groups: rec.audio.pro (More info?)

In article <2onkciFci068U1@uni-berlin.de> philallison@tpg.com.au writes:

> ** I gave the definition that all electro cap makers use - dickhead.

I've never seen a capacitor maker define the end of a capacitor's
life. Why would they?

> ** The ESR always goes high prior to loss of uFs.

Maybe that matters most, maybe something else matters most. You really
can't generalize these things unless you insist on being right all the
time.

--
I'm really Mike Rivers (mrivers@d-and-d.com)
However, until the spam goes away or Hell freezes over,
lots of IP addresses are blocked from this system. If
you e-mail me and it bounces, use your secret decoder ring
and reach me here: double-m-eleven-double-zero at yahoo
Anonymous
August 21, 2004 2:47:15 PM

Archived from groups: rec.audio.pro (More info?)

"Mike Rivers" <mrivers@d-and-d.com> wrote in message
news:znr1093052391k@trad
> In article <2onkciFci068U1@uni-berlin.de> philallison@tpg.com.au
> writes:
>
>> ** I gave the definition that all electro cap makers use -
>> dickhead.
>
> I've never seen a capacitor maker define the end of a capacitor's
> life. Why would they?

Because the life of electrolytic capacitors is a big issue. You need some
kind of a reliable measure of life to talk about it in a reasonable way.

ESR increase accelerates the failure of the cap. The ESR goes up because of
heating due energy being dissipated in the cap. The higher ESR causes more
energy to be dissipated in the cap, further raising the temperature of the
cap.
Anonymous
August 21, 2004 2:50:39 PM

Archived from groups: rec.audio.pro (More info?)

In article <znr1093085094k@trad>, Mike Rivers <mrivers@d-and-d.com> wrote:
>Can you point me to a good piece of reading matter on the subject,
>particularly relating ESR to failure modes? I thought I had a general
>idea of what ESR is and that it's desirable that a capacitor be
>designed and built so that it is as low as possible. From the bit of
>reading I've done, my sense is that this is a calculated value rather
>than one that's directly measured, and that what's measured is
>actually leakage (as well, of course, as capacitance) when evaluating
>the design and health of a capacitor.

Right. And in increase in ESR and change in value are both symptoms of
capacitor failure. The nice thing about ESR is that it changes pretty
dramatically before the value changes, and you can measure it in-circuit
very easily.

Leakage testing is also important because some types of capacitors fail
into leaks, but again leakage is hard to measure in-circuit in most
applications so it's less likely to be used for diagnostic testing.

A good introduction to this is the manual that came with the Heathkit
capacitor tester. I will see if I can dredge mine up out o the files.

>I wouldn't be surprised if one reason, perhaps the primary reason, for
>rising ESR over the life of a capacitor is deterioration of the
>electrolyte or deterioration of the plates, either of which could
>cause a reduction in capacitance. While ESR might be a good production
>line QA tool, if you wanted to know if a capacitor was still
>functional in situ, wouldn't it make more sense to measure the leakage
>(if its function is isolation) and capacitance (if its function is to
>create a frequency-dependent circuit)?

You have to take the device out of circuit to do that, unless the leakage
is greater than the parallel resistance from the accompanying circuit. The
nice thing about ESR testing is that it can easily be done in-circuit on
the fly, which makes it a great thing for repair technicians.

>I don't have to know why a power supply filter capacitor marked
>5,000 uF is, 27 years later, only 2,000 uF, but if it is, I can
>predict that there will be more ripple coming out of the power supply
>than the designer originally intended to live with. Therefore, the
>capacitor should be replaced.

Right. That capacitor will also display higher ESR and depending on what
sort it is, it might also have higher leakage. If it is bulged and cracked
with stuff coming out the side, this is another symptom of possible failure.

>Similarly, if a 100 uF coupling capacitor is now 5 uF, I can expect
>that unless the value was much greater than required by the design,
>low frequency response will be affected and the capacitor should be
>replaced.

Right.

>If, with or without a change in capacitance, the ESR has risen so that
>it acts like a resistor in series with the capacitor, I could also
>predict a change in frequency response. If the actual leakage has
>increased so that DC can flow through the capacitor, I could expect a
>bias problem if it was a coupling capacitor or a fuse blowing if it
>was a power supply filter.

Right.

>With all of those good diagnostic tools available, why worry about
>ESR? What else is there that a capacitor should do that would be
>predicted by an ESR measurement and not be apparent by some other
>bench diagnostic means?

By running a short pulse through the capacitor and measuring the
instantaneous series resistance, you don't have to take it out of
circuit because the accompanying shunt resistance of the circuit is
going to be much lower than the often sub-ohm resistance that you
are measuring. This makes it very convenient to check capacitors
without disconnecting them.

>If ESR manifests itself in the functional world as I think it does,
>the same thing that causes loss of capacitance is likely to cause a
>change in ESR. However, there may be applications for capacitors where
>ESR is not all that important as long as capacitance doesn't change
>along with it.

Right. But they do all change together, and all three of these parameters
are all symptoms of an internal failure.

>Bottom line - I think I can tell whether a capacitor is doing what
>it's supposed to do in the circuit in which it's installed without
>knowing anything about ESR. If I was designing a circuit, I might want
>to know about the ESR of the capacitor I intend to use becuase there
>may be advantages to choosing a capacitor with a low-ESR design.
>(Since this seems to be an advertised feature, I assume it increases
>cost, if for no other reason than to cover the cost of documentation
>and advertising.) Or it may be that for the function I intend for that
>capacitor, ESR (particularly over the product's expected lifetime) may
>not matter a bit, so I can make my marketing department happier by
>choosing a cheaper component.

Right. But ESR has become a de-facto bench measurement for capacitors
because it's easy to make.
--scott
--
"C'est un Nagra. C'est suisse, et tres, tres precis."
Anonymous
August 21, 2004 2:51:29 PM

Archived from groups: rec.audio.pro (More info?)

"Carey Carlan"


> What is the audible effect of aging capacitors? Should I start to hear
low
> level 60 Hz hum?


** There is no audible effect due to simply aging.

Caps that have failed due to loss of electrolyte with age may produce a
whole host of different symptoms.

If they are in the PSU then expect hum and even gross signal distortion .




.............. Phil
Anonymous
August 21, 2004 3:12:33 PM

Archived from groups: rec.audio.pro (More info?)

"Scott Dorsey"
> Phil Allison <

> >> What will I hear as these caps fade?
> >>
> >
> > ** Loss of lows, distortion, loss of volume.
> >
> > Replace them now - don't wait for symptoms.
>
> Wait a minute there, Phil. Aren't you the same guy who posted this?
>
> Phil Allison <philallison@tpg.com.au> wrote:
> > Kludge wrote:
> > > On typical pro audio gear, you may see a piece of equipment recapped
three
> > or four times over a 30-year lifespan.
> >
> > ** Not on the planet most people inhabit. Must be some idiot Yank idea
to
> > re-cap everything - the guitar amp loonies are always on about it as
some
> > sort of panacea.
>
> I see a discrepancy here.


** Where ??

The OP has a specific amp that is now 27 years old.

My advice was specific to that amp and specific caps on the PCB which have
shown to have short lives.




................ Phil
Anonymous
August 21, 2004 3:15:33 PM

Archived from groups: rec.audio.pro (More info?)

Scott Dorsey wrote:
>
>
> Both the Heathkit and the little kit ESR meter that Dick Smith sells

Searching around a bit, I also found the B&K <http://bkprecision.com/www/np_searchmodel7.asp?lf=ESR+M...;

Too bad this isn't a standard DVM function yet.




> charts that list minimal acceptable ESR for a given capacitance and
> voltage value. But it's really just a ballpark value, since capacitors
> all started out with very different ESR when they were new (compare a 1950's
> Mallory with a modern Panasonic FC, for instance). Can you really use
> the same standard on all of them? If your standard is too tight, you will
> be swapping those old 1950s Mallorys out even though they meet original
> specs. If your standard is too loose, you may miss some Panasonic FCs that
> are on their way to failing.

So is there a nice retro ESR table online somewhere?
Anonymous
August 21, 2004 3:42:49 PM

Archived from groups: rec.audio.pro (More info?)

In article <Hbqdnco7xtG2vrrcRVn-gA@comcast.com> arnyk@hotpop.com writes:

> the life of electrolytic capacitors is a big issue. You need some
> kind of a reliable measure of life to talk about it in a reasonable way.

This is probably still true with some equipment, but I'll bet there
are many more electrolytics used in equipment that will be in the
landfill long before the capacitors fail than there are electrolytics
in satellite electronics.

Let's remember where we are here.

> ESR increase accelerates the failure of the cap. The ESR goes up because of
> heating due energy being dissipated in the cap. The higher ESR causes more
> energy to be dissipated in the cap, further raising the temperature of the
> cap.

Thank you. That's a good reason why it's a concern. However this
suggests that ESR (the parameter) is an issue with THE CAPACITOR and
not with the circuit in which the capacitor is used. If this is true,
our phriend Phil is arguing what's a valid point but irrelevant to the
original discussion. As usual.


--
I'm really Mike Rivers (mrivers@d-and-d.com)
However, until the spam goes away or Hell freezes over,
lots of IP addresses are blocked from this system. If
you e-mail me and it bounces, use your secret decoder ring
and reach me here: double-m-eleven-double-zero at yahoo
Anonymous
August 21, 2004 5:40:09 PM

Archived from groups: rec.audio.pro (More info?)

In article <cg7nfv$i4v$1@panix1.panix.com> kludge@panix.com writes:

> >wouldn't it make more sense to measure the leakage
> >(if its function is isolation) and capacitance (if its function is to
> >create a frequency-dependent circuit)?
>
> You have to take the device out of circuit to do that, unless the leakage
> is greater than the parallel resistance from the accompanying circuit.

Well, you don't have to know exactly what the leakage is in order to
surmise that it's too much - like if there's DC where there shouldn't
be. Same with the capacitance value - if low frequency response is
falling off and a capacitor is the only thing in the way, then the
capactiance has likely dropped.

> The
> nice thing about ESR testing is that it can easily be done in-circuit on
> the fly, which makes it a great thing for repair technicians.

But you have to know what it's supposed to be. It's not marked on the
body of the capacitor like the capacitance and (often) the tolerance.
As far as leakage, "not enough to affect the circuit that's supposed
to not be getting any DC" is usually good enough. Generally if I can't
easily lift one end of a capacitor that behaves suspiciously in its
natural habitat, I won't be trying to fix it.

> By running a short pulse through the capacitor and measuring the
> instantaneous series resistance, you don't have to take it out of
> circuit because the accompanying shunt resistance of the circuit is
> going to be much lower than the often sub-ohm resistance that you
> are measuring. This makes it very convenient to check capacitors
> without disconnecting them.

But how do you know that they're bad? Is "normal" ESR a pretty
standard value for a known type of capacitor so the meter can have a "
"good/?/bad" scale that can be relied on? I've never used an ESR meter
and I'm not sure I've ever even seen one.

> Right. But ESR has become a de-facto bench measurement for capacitors
> because it's easy to make.

And I suppose that's a useful measurement if you know the expected
value (which I don't).

--
I'm really Mike Rivers (mrivers@d-and-d.com)
However, until the spam goes away or Hell freezes over,
lots of IP addresses are blocked from this system. If
you e-mail me and it bounces, use your secret decoder ring
and reach me here: double-m-eleven-double-zero at yahoo
Anonymous
August 21, 2004 7:53:00 PM

Archived from groups: rec.audio.pro (More info?)

"Arny Krueger"
> "Phil Allison"
> > "Carey Carlan"
> >
> >>> There are 100uF, 16 volt caps in the feedback that you should
> >>> replace -

> >> these are prone to drying out and losing all capacitance. Also
> >>> replace the bootstrap caps, 47 uF 100 volt for good measure.
>
> >> What will I hear as these caps fade?
>
> > ** Loss of lows, distortion, loss of volume.
>
> Let's go down Phil's list of symptoms and assign probable causes:
>


** Arny is about to publicly demonstrate his technical ignorance yet agian.



> Loss of lows - the cause must be partial loss of capacitance, as complete
> loss of capacitance would turn the amp into a unity gain amp.
>
> Distortion - could be leakage or increase of ESR, if nonlinear.


** Nope - failure of the bootstrap cap causes reduced drive to the
output devices.

The result is premature clipping on the positive side.



> Loss of volume - if it is truely just a loss of volume (flat frequency
> response), this is the only symptom that corresponds to a complete loss of
> capacitance,


** Nope - it corresponds to an increase in the ESR of the feedback cap.

If that 100uF cap developed 100 ohms of ESR then the channel's gain
drops by 3 dB.



> See former comments about unity gain.


** Why bother - Arny has not got the slightest clue.





........... Phil
Anonymous
August 21, 2004 7:53:01 PM

Archived from groups: rec.audio.pro (More info?)

"Phil Allison" <philallison@tpg.com.au> wrote in message
news:2oo69sFa0slvU1@uni-berlin.de
> "Arny Krueger"
>> "Phil Allison"
>>> "Carey Carlan"
>>>
>>>>> There are 100uF, 16 volt caps in the feedback that you should
>>>>> replace - these are prone to drying out and losing all
>>>>> capacitance. Also replace the bootstrap caps, 47 uF 100 volt for
>>>>> good measure.

>>>> What will I hear as these caps fade?

>>> ** Loss of lows, distortion, loss of volume.

>> Let's go down Phil's list of symptoms and assign probable causes:

> ** Arny is about to publicly demonstrate his technical ignorance yet
> agian.

Actually, I caught Phil in an error, below. It wouldn't be serious except
that he obviously thinks he's the height of perfection and I'm a silly ass.

>> Loss of lows - the cause must be partial loss of capacitance, as
>> complete loss of capacitance would turn the amp into a unity gain
>> amp.

>> Distortion - could be leakage or increase of ESR, if nonlinear.

> ** Nope - failure of the bootstrap cap causes reduced drive to the
> output devices.

Agreed, but I was thinking only of the feedback cap.

> The result is premature clipping on the positive side.

True, if I had been thinking about bootstrap caps. I wasn't.

>> Loss of volume - if it is truly just a loss of volume (flat
>> frequency response), this is the only symptom that corresponds to a
>> complete loss of capacitance,

> ** Nope - it corresponds to an increase in the ESR of the feedback
> cap.

> If that 100uF cap developed 100 ohms of ESR then the channel's
> gain drops by 3 dB.

Wrong. As long as there's a few uF capacitance in the capacitor, there's a
turnover point in the frequency response curve. Basic network analysis. It
ain't much of a turnover point, but there will be a measurable FR change.
Anonymous
August 21, 2004 7:55:27 PM

Archived from groups: rec.audio.pro (More info?)

"Arny Krueger" <

> It's possible that virtually every cap that has loss significant amounts
of
> capacitance, also has ESR problems.
>


** Short of physical damage - that is always the case.

ESR testers can * PREDICT * imminent capacitor failure.




........... Phil
Anonymous
August 21, 2004 9:05:48 PM

Archived from groups: rec.audio.pro (More info?)

"Arny Krueger"
> "Phil Allison
> >>>
> >>>>> There are 100uF, 16 volt caps in the feedback that you should
> >>>>> replace - these are prone to drying out and losing all
> >>>>> capacitance. Also replace the bootstrap caps, 47 uF 100 volt for
> >>>>> good measure.
>
> >>>> What will I hear as these caps fade?
>
> >>> ** Loss of lows, distortion, loss of volume.
>
> >> Let's go down Phil's list of symptoms and assign probable causes:
>
> > ** Arny is about to publicly demonstrate his technical ignorance yet
> > again.
>
> Actually, I caught Phil in an error, below.


** LIKE HELL.

Arny is about to publicly demonstrate his technical ignorance yet YET
again !!!!


> It wouldn't be serious except
> that he obviously thinks he's the height of perfection and I'm a silly
ass.


** Silly asses are all way ahead of Arny.


> >> Loss of lows - the cause must be partial loss of capacitance, as
> >> complete loss of capacitance would turn the amp into a unity gain
> >> amp.
>
> >> Distortion - could be leakage or increase of ESR, if nonlinear.
>
> > ** Nope - failure of the bootstrap cap causes reduced drive to the
> > output devices.
>
> Agreed, but I was thinking only of the feedback cap.


** Your mistake - dickhead.


> > The result is premature clipping on the positive side.
>
> True, if I had been thinking about bootstrap caps. I wasn't.


** Shame about that - the cap was mentioned in my prior comments.

You only had to ask me for the details.


>
> >> Loss of volume - if it is truly just a loss of volume (flat
> >> frequency response), this is the only symptom that corresponds to a
> >> complete loss of capacitance,
>
> > ** Nope - it corresponds to an increase in the ESR of the feedback
> > cap.
>
> > If that 100uF cap developed 100 ohms of ESR then the channel's
> > gain drops by 3 dB.

>
> Wrong.


** Nope - Arny is *dead wrong* - yet AGAIN !!!!!


> As long as there's a few uF capacitance in the capacitor, there's a
> turnover point in the frequency response curve. Basic network analysis. It
> ain't much of a turnover point, but there will be a measurable FR change.


** ESR is the issue - the "S" in ESR stands for "series ". Any ESR
associated with that 100uf cap *adds* to the value of 270 ohm resistor in
the feedback network and reduces the amp's gain.

Now, will Arny have the decency to apologise ??

Will he ever wake up he is not competent on this topic ??




............. Phil
Anonymous
August 21, 2004 9:05:49 PM

Archived from groups: rec.audio.pro (More info?)

"Phil Allison" <philallison@tpg.com.au> wrote in message
news:2ooaidFd1c6pU1@uni-berlin.de
>
>> As long as there's a few uF capacitance in the capacitor, there's a
>> turnover point in the frequency response curve. Basic network
>> analysis. It ain't much of a turnover point, but there will be a
>> measurable FR change.

>
> ** ESR is the issue - the "S" in ESR stands for "series ". Any
> ESR associated with that 100uf cap *adds* to the value of 270 ohm
> resistor in the feedback network and reduces the amp's gain.

Exactly. So work out the frequency response of the origional network, and
the new network.

You'll find that the small capacitance of the partially-failed shunt
capacitor and it higher ESR can create a frequency-sensitive network.
Anonymous
August 22, 2004 12:25:38 AM

Archived from groups: rec.audio.pro (More info?)

"Arny Krueger"
> "Phil Allison"


** Arny is trying to shift the context again - so I had to put it back.


> > If that 100uF cap developed 100 ohms of ESR then the channel's
> > gain drops by 3 dB.

>> Wrong.

** Nope - Arny is *dead wrong* - yet AGAIN !!!!!

> >
> >> As long as there's a few uF capacitance in the capacitor, there's a
> >> turnover point in the frequency response curve. Basic network
> >> analysis. It ain't much of a turnover point, but there will be a
> >> measurable FR change.
>
> >
> > ** ESR is the issue - the "S" in ESR stands for "series ". Any
> > ESR associated with that 100uf cap *adds* to the value of 270 ohm
> > resistor in the feedback network and reduces the amp's gain.
>
>
> Exactly.


** So Arny admits he was wrong.


> So work out the frequency response of the origional network, and
> the new network.


** I already did - it is still flat.

The extra 100 ohms only reduces the gain.



> You'll find that the small capacitance of the partially-failed shunt
> capacitor and it higher ESR can create a frequency-sensitive network.
>


** That is a really desperate attempt to move the context.

There need not be any loss of capacitance with a rise in the ESR.

What a despicable fake you are Arny.




.............. Phil
Anonymous
August 22, 2004 12:38:34 AM

Archived from groups: rec.audio.pro (More info?)

In article <znr1093104445k@trad>, Mike Rivers <mrivers@d-and-d.com> wrote:
>In article <cg7nfv$i4v$1@panix1.panix.com> kludge@panix.com writes:
>> The
>> nice thing about ESR testing is that it can easily be done in-circuit on
>> the fly, which makes it a great thing for repair technicians.
>
>But you have to know what it's supposed to be. It's not marked on the
>body of the capacitor like the capacitance and (often) the tolerance.
>As far as leakage, "not enough to affect the circuit that's supposed
>to not be getting any DC" is usually good enough. Generally if I can't
>easily lift one end of a capacitor that behaves suspiciously in its
>natural habitat, I won't be trying to fix it.

No, but you can use a cheat sheet to get a good notion of what it ought
to be, and usually when it is off, it is so far off that it's easy to
see that it's bad. ESR is honestly the most convenient way for finding
bad capacitors in equipment, and I have saved so much time since I bought
an ESR tester that I don't know what I did before I had it.

>> By running a short pulse through the capacitor and measuring the
>> instantaneous series resistance, you don't have to take it out of
>> circuit because the accompanying shunt resistance of the circuit is
>> going to be much lower than the often sub-ohm resistance that you
>> are measuring. This makes it very convenient to check capacitors
>> without disconnecting them.
>
>But how do you know that they're bad? Is "normal" ESR a pretty
>standard value for a known type of capacitor so the meter can have a "
>"good/?/bad" scale that can be relied on? I've never used an ESR meter
>and I'm not sure I've ever even seen one.

If you know the voltage and you know the capacitance, you know more or
less how much ESR a typical capacitor is going to have using the cheat
sheet. Higher grade switching supply types will have less, but if they
get to the point where they have more, they are bad. Usually the ESR
rise is high enough that it's easy to tell.

>> Right. But ESR has become a de-facto bench measurement for capacitors
>> because it's easy to make.
>
>And I suppose that's a useful measurement if you know the expected
>value (which I don't).

You want a Heatkit capacitor tester? I got a fancy digital one now and
I hardly ever use it these days, but it comes with the cheat sheet.
--scott
--
"C'est un Nagra. C'est suisse, et tres, tres precis."
Anonymous
August 22, 2004 12:42:48 AM

Archived from groups: rec.audio.pro (More info?)

"Arny Krueger" <
> "Mike Rivers"
>> Phil Allison
> >
> >> ** I gave the definition that all electro cap makers use -
> >> dickhead.
> >
> > I've never seen a capacitor maker define the end of a capacitor's
> > life. Why would they?
>
> Because the life of electrolytic capacitors is a big issue. You need some
> kind of a reliable measure of life to talk about it in a reasonable way.
>
>
> ESR increase accelerates the failure of the cap. The ESR goes up because
of
> heating due energy being dissipated in the cap. The higher ESR causes more
> energy to be dissipated in the cap, further raising the temperature of the
> cap.
>


** Increased temperature actually **reduces** the ESR of an electro - at
80 degrees C it is about 5 times less than at 20 degrees C. This is due
simply the electrolyte becoming more conductive when hot.

The cause of ESR rising ( in a given cap at a given temp) is loss of
electrolyte via imperfect seals - a process that accelerates at higher
temps.




............ Phil
Anonymous
August 22, 2004 12:42:49 AM

Archived from groups: rec.audio.pro (More info?)

"Phil Allison" <philallison@tpg.com.au> wrote in message
news:2oon9aFb1scrU2@uni-berlin.de
> "Arny Krueger" <
>> "Mike Rivers"
>>> Phil Allison
>>>
>>>> ** I gave the definition that all electro cap makers use -
>>>> dickhead.
>>>
>>> I've never seen a capacitor maker define the end of a capacitor's
>>> life. Why would they?
>>
>> Because the life of electrolytic capacitors is a big issue. You need
>> some kind of a reliable measure of life to talk about it in a
>> reasonable way.
>>
>>
>> ESR increase accelerates the failure of the cap. The ESR goes up
>> because of heating due energy being dissipated in the cap. The
>> higher ESR causes more energy to be dissipated in the cap, further
>> raising the temperature of the cap.
>>
>
>
> ** Increased temperature actually **reduces** the ESR of an electro
> - at 80 degrees C it is about 5 times less than at 20 degrees C.
> This is due simply the electrolyte becoming more conductive when hot.


Like all generalities, this is falsified by actual vendor data:

http://www.powerdesigners.com/InfoWeb/design_center/Des...

shows a plot of ESR versus temperature and frequency.

First off, we see that ESR is sometimes an increasing function of
temperature and sometimes a decreasing function of temperature.

ESR is generally sharply decreasing at sub-freezing temperatures.

Examining the plot more closely, we see that at low frequencies below 100
KHz (audio & power frequencies) and above about 30C, ESR is an increasing
function of temperature. IOW under typical audio equipment temperature and
frequencies, ESR increases with temperature.

Perhaps other capacitors perform differently.
http://www.cornell-dubilier.com/applets/CDEspiceApplet/...
suggests they do.


> The cause of ESR rising ( in a given cap at a given temp) is loss of
> electrolyte via imperfect seals - a process that accelerates at higher
> temps.

But it seems like Phil previously said that capacitance does not decrease
significantly over the life of a cap. This begs the question of how a
capacitor has constant capacitance with decreasing electrolyte.
Anonymous
August 22, 2004 12:42:49 AM

Archived from groups: rec.audio.pro (More info?)

In article <2oon9aFb1scrU2@uni-berlin.de> philallison@tpg.com.au writes:

> The cause of ESR rising ( in a given cap at a given temp) is loss of
> electrolyte via imperfect seals - a process that accelerates at higher
> temps.

Does loss of electrolyte cause reduction in capacitance? Can we get
back to the reason why we care about ESR instead of that the marketing
department likes good numbers? Most of us don't go around measuring
capacitors to see if they're on the road to failure (we already know they
are, from the moment we put them into service) but we can tell when
they have failed.




--
I'm really Mike Rivers (mrivers@d-and-d.com)
However, until the spam goes away or Hell freezes over,
lots of IP addresses are blocked from this system. If
you e-mail me and it bounces, use your secret decoder ring
and reach me here: double-m-eleven-double-zero at yahoo
Anonymous
August 22, 2004 12:44:47 AM

Archived from groups: rec.audio.pro (More info?)

"Mike Rivers"
>

>
> > What is the audible effect of aging capacitors? Should I start to hear
low
> > level 60 Hz hum?
>
> If it's a power supply filter that isn't filtering like it should,
> yes. Actually, you'll most likely hear 120 Hz hum because just about
> every power supply uses a full wave rectifier.
>


** Not so for voltage doubler PSUs - they are full wave but each cap
sees 60 Hz ripple.




........... Phil
Anonymous
August 22, 2004 12:44:48 AM

Archived from groups: rec.audio.pro (More info?)

In article <2ooncvFd86m4U1@uni-berlin.de> philallison@tpg.com.au writes:

> ** Not so for voltage doubler PSUs - they are full wave but each cap
> sees 60 Hz ripple.

Making an around-the-corner point just for the sake of argument again.
But this is typical for the loser-who-refuses-to-lose.



--
I'm really Mike Rivers (mrivers@d-and-d.com)
However, until the spam goes away or Hell freezes over,
lots of IP addresses are blocked from this system. If
you e-mail me and it bounces, use your secret decoder ring
and reach me here: double-m-eleven-double-zero at yahoo
Anonymous
August 22, 2004 2:13:06 AM

Archived from groups: rec.audio.pro (More info?)

Kurt Albershardt <kurt@nv.net> wrote:
>Scott Dorsey wrote:
>>
>> Both the Heathkit and the little kit ESR meter that Dick Smith sells
>
>Searching around a bit, I also found the B&K <http://bkprecision.com/www/np_searchmodel7.asp?lf=ESR+M...;
>
>Too bad this isn't a standard DVM function yet.

The capacitor tester in my DVM actually is a relaxation oscillator with an
RC time constant, the C being the device under test, going into a frequency
counter. If the capacitor is leaky or has excessively high ESR, the value
will test as incorrect. It's actually very handy but only out of circuit.
Unfortunately it also reads in nF, which I can't think in easily.
--scott
--
"C'est un Nagra. C'est suisse, et tres, tres precis."
Anonymous
August 22, 2004 6:01:40 AM

Archived from groups: rec.audio.pro (More info?)

Mike Rivers wrote:

> In article <2onkciFci068U1@uni-berlin.de> philallison@tpg.com.au writes:
>
> > ** I gave the definition that all electro cap makers use - dickhead.
>
> I've never seen a capacitor maker define the end of a capacitor's
> life. Why would they?

Because parameters change with 'load life'.

I've never seen a data sheet refer to life vs ESR though.

Here's a typical one.

http://www.sterling-comp.co.uk/PDFs/Nippon_Chemi_Con/SM...

'Endurance' is specified thus :

The following specifications shall be satisfied when the capacitors are
restored to 20C after subjected to DC voltage with the rated ripple current is
applied for 2000 hours at 85C.
Capacitance change <= +/- 20% of the initial value
D.F. (tan delta) <= +/- 200% of the initial specified value
Leakage current <= The initial specified value


Graham
Anonymous
August 22, 2004 7:49:58 AM

Archived from groups: rec.audio.pro (More info?)

Scott Dorsey wrote:

> Kurt Albershardt <kurt@nv.net> wrote:
> >Scott Dorsey wrote:
> >>
> >> Both the Heathkit and the little kit ESR meter that Dick Smith sells
> >
> >Searching around a bit, I also found the B&K <http://bkprecision.com/www/np_searchmodel7.asp?lf=ESR+M...;
> >
> >Too bad this isn't a standard DVM function yet.
>
> The capacitor tester in my DVM actually is a relaxation oscillator with an
> RC time constant, the C being the device under test, going into a frequency
> counter. If the capacitor is leaky or has excessively high ESR, the value
> will test as incorrect. It's actually very handy but only out of circuit.
> Unfortunately it also reads in nF, which I can't think in easily.

I tend to find the classic 0.001 uF a little tiresome myself. Don't appreciate any zeroes after the decimal
point myself.

Graham


p.s. was reading an old text book recently and had to stop to think about values in uuF !
!