Audio amplifier repair - bad capacitors

[M.Joshi]

Hello,

When repairing audio amplifiers, would an ESR meter or a capacitanc
meter be more useful in identifying bad capacitors in circuit?

Would either of these be any good:

'High Precision L/C Inductance Inductor Capacitance Multimeter Mete
LC200A Tool | eBay' (http://tinyurl.com/prdtqh7)

'Capacitor/Capacitance ESR IN-Circuit Inductance Resistance Meter L
Meter dc 9v | eBay' (Error)


Thanks


--
M.Joshi

 

[John Robertson]

On 07/14/2013 8:35 AM, M.Joshi wrote:

Hello,

When repairing audio amplifiers, would an ESR meter or a capacitance
meter be more useful in identifying bad capacitors in circuit?

Would either of these be any good:

'High Precision L/C Inductance Inductor Capacitance Multimeter Meter
LC200A Tool | eBay' (http://tinyurl.com/prdtqh7)

'Capacitor/Capacitance ESR IN-Circuit Inductance Resistance Meter LC
Meter dc 9v | eBay' (Error)


Thanks.

I've been selling the Bob Parker ESR meters (now BLUE) kit since 1999
and they has been a great boon to technicians for fixing monitors,
switching power supplies, and other devices with electrolytic
capacitors. Great for caps larger than around 2ufd.

https://www.flippers.com/BlueEsr.html

Unfortunately smaller value caps (<2ufd) are harder to check in circuit
and I can't speak to the ones on eBay. They may or may not live up to
the ad.

I do know that Bob Parker's design works for our shop - that's why I've
been happily selling them!

http://www.flippers.com/catalog/index.php/test-equipment-kits-c-3

John :-#)#

--
(Please post followups or tech enquiries to the newsgroup)
John's Jukes Ltd. 2343 Main St., Vancouver, BC, Canada V5T 3C9
Call (604)872-5757 or Fax 872-2010 (Pinballs, Jukes, Video Games)
www.flippers.com
"Old pinballers never die, they just flip out."

 

On 2013-07-14 17:35:11 +0200, M.Joshi <M.Joshi.c28845d@diybanter.com> said:

Hello,

When repairing audio amplifiers, would an ESR meter or a capacitance
meter be more useful in identifying bad capacitors in circuit?

Would either of these be any good:

'High Precision L/C Inductance Inductor Capacitance Multimeter Meter
LC200A Tool | eBay' (http://tinyurl.com/prdtqh7)

'Capacitor/Capacitance ESR IN-Circuit Inductance Resistance Meter LC
Meter dc 9v | eBay' (Error)


Thanks.

I dont think esr can prevent audio amplifiers from working
it prevents power supplies (especially switching) yes
there are lot of switching power supplies that may fail due to bad esr
capacitor
but in an audio amplifier there is quite never a switching power supply

but an esr meter is very useful to the technician
but if you do only audio repair, you won't use it very often.

see below my web site for free esr schematics
--
----------
Kripton

the ESR Repository @ http://kripton2035.free.fr/esr-repository.html
the Geiger Repository @ http://kripton2035.free.fr/geiger-repositor.html

 

[tm]

"John Robertson" <spam@flippers.com> wrote in message
news:wv2dnWu3HKMMSH_MnZ2dnUVZ_qqdnZ2d@giganews.com...

On 07/14/2013 8:35 AM, M.Joshi wrote:
Hello,

When repairing audio amplifiers, would an ESR meter or a capacitance
meter be more useful in identifying bad capacitors in circuit?

Would either of these be any good:

'High Precision L/C Inductance Inductor Capacitance Multimeter Meter
LC200A Tool | eBay' (http://tinyurl.com/prdtqh7)

'Capacitor/Capacitance ESR IN-Circuit Inductance Resistance Meter LC
Meter dc 9v | eBay' (Error)


Thanks.





I've been selling the Bob Parker ESR meters (now BLUE) kit since 1999 and
they has been a great boon to technicians for fixing monitors, switching
power supplies, and other devices with electrolytic capacitors. Great for
caps larger than around 2ufd.

https://www.flippers.com/BlueEsr.html

Unfortunately smaller value caps (<2ufd) are harder to check in circuit
and I can't speak to the ones on eBay. They may or may not live up to the
ad.

I do know that Bob Parker's design works for our shop - that's why I've
been happily selling them!

http://www.flippers.com/catalog/index.php/test-equipment-kits-c-3

John :-#)#

--

+1.

The Blue ESR meter saves a lot of time. Often the biggest delay is waiting
on the spare parts.

tm

 

[tm]

<Kripton> wrote in message news:51e2dbf7$0$2410$426a74cc@news.free.fr...

On 2013-07-14 17:35:11 +0200, M.Joshi <M.Joshi.c28845d@diybanter.com
said:


Hello,

When repairing audio amplifiers, would an ESR meter or a capacitance
meter be more useful in identifying bad capacitors in circuit?

Would either of these be any good:

'High Precision L/C Inductance Inductor Capacitance Multimeter Meter
LC200A Tool | eBay' (http://tinyurl.com/prdtqh7)

'Capacitor/Capacitance ESR IN-Circuit Inductance Resistance Meter LC
Meter dc 9v | eBay' (Error)


Thanks.

I dont think esr can prevent audio amplifiers from working
it prevents power supplies (especially switching) yes
there are lot of switching power supplies that may fail due to bad esr
capacitor
but in an audio amplifier there is quite never a switching power supply

but an esr meter is very useful to the technician
but if you do only audio repair, you won't use it very often.

see below my web site for free esr schematics
--
----------
Kripton

Don't work on many amps, do you?

Class D are all switching units. The power supply as well as the amp.

 

[Michael Black]

On Sun, 14 Jul 2013, tm wrote:

Kripton> wrote in message news:51e2dbf7$0$2410$426a74cc@news.free.fr...
On 2013-07-14 17:35:11 +0200, M.Joshi <M.Joshi.c28845d@diybanter.com> said:


Hello,

When repairing audio amplifiers, would an ESR meter or a capacitance
meter be more useful in identifying bad capacitors in circuit?

Would either of these be any good:

'High Precision L/C Inductance Inductor Capacitance Multimeter Meter
LC200A Tool | eBay' (http://tinyurl.com/prdtqh7)

'Capacitor/Capacitance ESR IN-Circuit Inductance Resistance Meter LC
Meter dc 9v | eBay' (Error)


Thanks.

I dont think esr can prevent audio amplifiers from working
it prevents power supplies (especially switching) yes
there are lot of switching power supplies that may fail due to bad esr
capacitor
but in an audio amplifier there is quite never a switching power supply

but an esr meter is very useful to the technician
but if you do only audio repair, you won't use it very often.

see below my web site for free esr schematics
--
----------
Kripton


Don't work on many amps, do you?

Class D are all switching units. The power supply as well as the amp.

I think the point is that generally audio amplifiers these days don't have

that many electrolytic capacitors. The circuitry is generally direct
coupled, even at the output. That's a big difference from early
transistor amplifiers that suddenly used a slew of electrolytics.

And most amplifiers still use linear power supplies, so not only are the
filter capacitors operating at a relatively low frequency, but they are
few in number. If you've got hum from the amplifier, chances are the
filter capacitor is bad. IN a switching supply, the supply may never
start working if an electrolytic is bad.

Like I said earlier, one reason for ESR meters is the rise in the number
of electrolytics. If you can't easily tell which is causing the problem,
it makes sense to have a meter that will check the electrolytics in
circuit. Especially if the circuit is still relatively "foreign" like a
switching supply or other digital circuitry. An audio amplifier is
generally still a familiar thing, check where the audio disappears, check
for voltages, etc. There are a lot ore telltales than in a switching
supply where mutliple things interact and still many people haven't had
much experience with them.

In antique radio circles, it's all so much easier. 2 or 3 electrolytics,
might as well just replace them, if they aren't bad now, they will go bad.
ANd yes, if it's old enough, just replace the other capacitors, since old
enough means odd types of capacitors that can go bad. The electrolytics
are easy, not many of them. The others people know from experience, so
if you've got the radio open, might as well do them all.

Even odler transistor radios tend to get th shotgun treatment. There are
more electrolytics than in tubes, but still not that many and likely froma
period when they would be failing by now. But again since the number are
few, it;'s just as easy to replace them as to spend time trying to figure
out what's wrong.

In modern equipment, not generally audio amplifiers, the circuit isn't
obvious (and often no schematic), and so many electrolytics that it starts
being cheaper to find the bad ones than just shotgun them all.

It really depends. For someone just doing amplifiers, an ESR meter might
not be that useful, they have other means of evaluating things. If they
did other things, then an ESR meter becomes valuable, and then they can
use it on amplifiers, too.

Michael

 

[David Platt]

In article <M.Joshi.c28845d@diybanter.com>,
M.Joshi <M.Joshi.c28845d@diybanter.com> wrote:

Hello,

When repairing audio amplifiers, would an ESR meter or a capacitance
meter be more useful in identifying bad capacitors in circuit?

I would definitely want one with ESR-measuring capabilities. From
what I've read (and in my own experience), electrolytic caps which
start to fail will usually show a significant increase in ESR well
before their capacitance changes significantly.

Would either of these be any good:

'High Precision L/C Inductance Inductor Capacitance Multimeter Meter
LC200A Tool | eBay' (http://tinyurl.com/prdtqh7)

That one looks similar to the AADE meter (http://aade.com/lcmeter.htm)
and might be one of the "knock-offs" that this page refers to.

I do like the AADE meter - it seems to work very well for what it's
intended to do. It does capacitance measurements over a wide range
(pF up to 1.5 uF).

However, it is not intended or advertised as being useful for
in-circuit measurements, it doesn't have ESR-measuring capability, and
it isn't designed to measure the capacitance of all but the smallest
electrolytic caps.

'Capacitor/Capacitance ESR IN-Circuit Inductance Resistance Meter LC
Meter dc 9v | eBay' (Error)

The one I see with this description looks more like what you'd
want... its capacitance measurement range covers typical electrolytics
(but not smaller film/ceramic caps), and it does multi-frequency
measurements which will give you both the capacitance and the ESR.

The two types of meters you've described here are really complementary
sorts of instruments... they both measure capacitors, but their ranges
of measurements barely overlap. They're both useful but do different
sorts of things, and you wouldn'd do wrong by having one of each type.

The third type of measurement you might want to do for looking at
failed caps in an audio amp, would be a leakage test. Inter-stage
coupling caps can become leaky, especially if there's no bias voltage
across them most of the time (or if they're reverse biased) and this
isn't something which will show up in a capacitance or ESR test.
Testing for leaky 'lytics is probably best done out-of-circuit,
though.

I built my own ESR meter a few years ago, based on the Ludens design
(http://ludens.cl/Electron/esr/esr.html) and it's been quite useful.
Easily made using "junk box" parts, capable of doing in-circuit ESR
measurements safely, and un-critical in its construction, it's a great
weekend project.

 

[Jeff Liebermann]

On Sun, 14 Jul 2013 17:35:11 +0200, M.Joshi
<M.Joshi.c28845d@diybanter.com> wrote:

When repairing audio amplifiers, would an ESR meter or a capacitance
meter be more useful in identifying bad capacitors in circuit?

An ESR meter is a VERY useful tool for finding bad caps.

Most of these were found with an ESR meter over about a 3 month
period:
<http://802.11junk.com/jeffl/pics/repair/slides/bad-caps.html>
While some of these caps show obvious bulges, many of them have no
visible signs of failure.

Would either of these be any good:

'High Precision L/C Inductance Inductor Capacitance Multimeter Meter
LC200A Tool | eBay' (http://tinyurl.com/prdtqh7)

No. That's an L/C meter, not an ESR meter. You can have a bad
capacitor, with a very high ESR and still show normal capacitance.

'Capacitor/Capacitance ESR IN-Circuit Inductance Resistance Meter LC
Meter dc 9v | eBay' (Error)

No experience with that one. I'm suspicious because it doesn't say
anything about zeroing the probe cable resistance, which is necessary
for in-circuit measurements.

Search for one of the Bob Parker ESR meter designs. I have one of the
original Dick Smith variety. Works nicely.
<http://members.ozemail.com.au/~bobpar/esrmeter.htm>
I suggest you read a little about how an ESR meter is used before
buying.


--
Jeff Liebermann jeffl@cruzio.com
150 Felker St #D http://www.LearnByDestroying.com
Santa Cruz CA 95060 http://802.11junk.com
Skype: JeffLiebermann AE6KS 831-336-2558

 

[Jeff Liebermann]

On Sun, 14 Jul 2013 14:11:11 -0400, Michael Black <et472@ncf.ca>
wrote:

I think the point is that generally audio amplifiers these days don't have
that many electrolytic capacitors. The circuitry is generally direct
coupled, even at the output. That's a big difference from early
transistor amplifiers that suddenly used a slew of electrolytics.

I beg to differ slightly. Here's a lousy photo of the power amp and
power supply section from a Behringer PMH518M mono amplifier that had
a problem with bad capacitors:
<http://802.11junk.com/jeffl/pics/repair/slides/Behringer-PMH518M-PS.html>
The two big caps (C6, C7), that are missing in the photo, were the
primary culprits[1]. Their high ESR caused major voltage excursions
to the regulator transistors, sufficient to blow up the devices and
fry the traces. Other than some corrosive goo leaking from the rubber
seal on the bottom of the caps, there was no visible evidence that the
caps were not doing their job. I didn't need an ESR meter to fix such
an obvious problem, but with less damage, it might have been helpful
to verify that the caps were still usable.

I don't do much audio or video repair, but I am beginning to see Class
E switched amplifiers, mostly in computah speakers, which more
closesly resemble a switching power supply than a traditional linear
power amplifier. I would expect capacitor ESR problems in those.


[1] Hint: The caps are 4700uf 50VDC running on a 40 VDC input bus to
the regulators. Running caps at 80% of the maximum voltage, next to a
heat sink full of very warm devices, is not a great design, even at
120Hz. I replaced them with 3300uf 63VDC caps.

--
Jeff Liebermann jeffl@cruzio.com
150 Felker St #D http://www.LearnByDestroying.com
Santa Cruz CA 95060 http://802.11junk.com
Skype: JeffLiebermann AE6KS 831-336-2558

 

[John-Del]

On Sunday, July 14, 2013 1:12:23 PM UTC-4, Kripton wrote:

I dont think esr can prevent audio amplifiers from working

it prevents power supplies (especially switching) yes

there are lot of switching power supplies that may fail due to bad esr

capacitor

but in an audio amplifier there is quite never a switching power supply

There are still a significant number of older audio amplifiers that use electrolytics in the coupling mode, so I guess an ESR meter is handy.

I have a Parker ESR meter and an older Sencore Z meter. Both have on occasion reported normal ESR in an in circuit test that was false ie: removed cap showed bad ESR out of circuit, and the circuit-sans cap, still showed good ESR with no cap installed). BTW, beware the resident troll that will pop up shortly and spew his vile garbage. Regulars are already ducking...

What I do now is mostly use my scope with the equipment up and running for both bypass and coupling caps. Anything that doesn't look right gets pulled and checked on the Sencore for ESR, full voltage leakage, then recheck for ESR.

 

[Phil Allison]

"M.Joshi"

When repairing audio amplifiers, would an ESR meter or a capacitance
meter be more useful in identifying bad capacitors in circuit?

** An ESR meter is the only useful type.

The best one for all servicing work is the "Bob Parker" ESR and Low Ohms
meter:

Just Google that name for heaps of hits.




.... Phil

 

[Phil Allison]

"M.Joshi"

When repairing audio amplifiers, would an ESR meter or a capacitance
meter be more useful in identifying bad capacitors in circuit?

** An ESR meter is the only useful type.

The best one for all servicing work is the "Bob Parker" ESR and Low Ohms
meter:

Just Google that name for heaps of hits.




.... Phil

 

[Phil Allison]

"M.Joshi"

When repairing audio amplifiers, would an ESR meter or a capacitance
meter be more useful in identifying bad capacitors in circuit?

** An ESR meter is the only useful type.

The best one for all servicing work is the "Bob Parker" ESR and Low Ohms
meter:

Just Google that name for heaps of hits.




.... Phil

 

[Phil Allison]

<Kripton>

When repairing audio amplifiers, would an ESR meter or a capacitance
meter be more useful in identifying bad capacitors in circuit?

I dont think esr can prevent audio amplifiers from working
it prevents power supplies (especially switching) yes
there are lot of switching power supplies that may fail due to bad esr
capacitor
but in an audio amplifier there is quite never a switching power supply

but an esr meter is very useful to the technician
but if you do only audio repair, you won't use it very often.

** Nonsense.

Electro caps get old and wear out no matter what gear they are in - heat is
the main cause.

Audio amps get hot, tube ones very much so.

High ESR caps in an amplifier will cause hum, high and low frequency
instability, loss of gain and even loss of signal entirely.

A good ESR meter allows you to find then before symptoms appear too.


.... Phil

 

[Arfa Daily]

"Kripton" wrote in message news:51e2dbf7$0$2410$426a74cc@news.free.fr...

On 2013-07-14 17:35:11 +0200, M.Joshi <M.Joshi.c28845d@diybanter.com
said:


Hello,

When repairing audio amplifiers, would an ESR meter or a capacitance
meter be more useful in identifying bad capacitors in circuit?

Would either of these be any good:

'High Precision L/C Inductance Inductor Capacitance Multimeter Meter
LC200A Tool | eBay' (http://tinyurl.com/prdtqh7)

'Capacitor/Capacitance ESR IN-Circuit Inductance Resistance Meter LC
Meter dc 9v | eBay' (Error)


Thanks.

I dont think esr can prevent audio amplifiers from working
it prevents power supplies (especially switching) yes
there are lot of switching power supplies that may fail due to bad esr
capacitor
but in an audio amplifier there is quite never a switching power supply

but an esr meter is very useful to the technician
but if you do only audio repair, you won't use it very often.

see below my web site for free esr schematics
--
----------
Kripton

Not true on several counts. I am seeing more and more switchers in consumer
audio gear, and electrolytics fail in all sorts of areas in amplifiers, not
just power supplies. But even that doesn't go against the usefulness of an
ESR meter with audio gear, because even if the amplifier in question has a
linear supply, caps still go high ESR and cause problems. I replace them
every working week in every area of every type of equipment.

Arfa

 

[Arfa Daily]

"Phil Allison" <phil_a@tpg.com.au> wrote in message
news:b4gsibF967oU1@mid.individual.net...

Kripton

When repairing audio amplifiers, would an ESR meter or a capacitance
meter be more useful in identifying bad capacitors in circuit?

I dont think esr can prevent audio amplifiers from working
it prevents power supplies (especially switching) yes
there are lot of switching power supplies that may fail due to bad esr
capacitor
but in an audio amplifier there is quite never a switching power supply

but an esr meter is very useful to the technician
but if you do only audio repair, you won't use it very often.


** Nonsense.

Electro caps get old and wear out no matter what gear they are in - heat
is the main cause.

Audio amps get hot, tube ones very much so.

High ESR caps in an amplifier will cause hum, high and low frequency
instability, loss of gain and even loss of signal entirely.

A good ESR meter allows you to find then before symptoms appear too.


... Phil

I'm with you all the way on this one, Phil

Arfa

 

[Phil Allison]

"Arfa Daily"

but an esr meter is very useful to the technician
but if you do only audio repair, you won't use it very often.

see below my web site for free esr schematics
--
----------
Kripton


Not true on several counts. I am seeing more and more switchers in
consumer audio gear, and electrolytics fail in all sorts of areas in
amplifiers, not just power supplies. But even that doesn't go against the
usefulness of an ESR meter with audio gear, because even if the amplifier
in question has a linear supply, caps still go high ESR and cause
problems. I replace them every working week in every area of every type of
equipment.

** A recent example of using my Bob Parker ESR meter was with a nicely made
clone of a Fender "Princeton Reverb" combo amp. The amp was just a few years
old and had all new components in it - PLUS a chassis made from Stainless
Steel !!

However, it was riddled with faults like low frequency oscillation (
motor-boating), loud hum and high frequency instability when the reverb was
turned up.

The ESR meter read off scale ( ie over 100ohms) on three sections of the
main filter electro and 20 ohms on the fourth - it was one of these:

http://www.tubesandmore.com/products/C-EC20X4-475

New electros fixed all the faults.

When I opened the can of the old one, the aluminium strips linking the
terminals to the insides were mostly eaten away with horrible corrosion.

My conclusion is that the electro was far from new - more likely 50 year
old stock that someone has found and re-labelled.

BTW:

Old electros can often still work fine, but not if left in storage for
periods like 50 years.



..... Phil