Caps in amps

[Guest]

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

 

[Guest]

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

 

[Guest]

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."

 

[Guest]

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

 

[Guest]

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

 

[Guest]

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...

 

[Guest]

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

 

[Guest]

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

 

[Guest]

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.

 

[Guest]

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

 

[Guest]

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!

 

[Guest]

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

 

[Agent86]

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.

 

[Guest]

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?

 

[Guest]

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."

 

[Guest]

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?

 

[Guest]

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.

 

[Guest]

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.

 

[Guest]

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.

 

[Guest]

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