My approx 9 year old AV amp started buzzing / humming sounds like
100Hz, slowly got louder until drowning out the music ! PSU caps I
should think. They are labeled "kenwood for audio".
I've got the bigs caps out, they are 10000uF 80V. Lots around for
about 20quid each, or some ebay ones which I try to avoid if possible.
Does this look OK ?
http://connect-audio.co.uk/proddetai...000U80&cat=219
Does the life seem a bit short (I know this is at the max temp) ?

Also saw this but the lead spacing and layout is wrong:
http://parts.digikey.co.uk/1/1/91787...t1ka103fa.html

I did not realise the life was so limited though. I've left the amp on
24 hours a day on standby for years !

Also a couple of smaller 3300uF 50V jobs, I guess for a 5V or similar
supply for the ICs, DSP chips etc.
Probably worth changing those as well.

OR ..
Is this really worth my time and up to 50 quid fixing ???
A new replacement would cost 350 quid but would support blue ray
audio, HDMI etc.

Simon.

At that price I'd want to be certain it was those caps. Can you isolate
the main amps or perhaps short the inputs to be certain it isn't coming
from elsewhere?

I've got several amps here a lot older than that on the original smoothing
caps.

--
*When I'm not in my right mind, my left mind gets pretty crowded *

Dave Plowman London SW
To e-mail, change noise into sound.

On Mar 3, 11:33*pm, sm_jamieson wrote:

My approx 9 year old AV amp started buzzing / humming sounds like
100Hz, slowly got louder until drowning out the music ! PSU caps I
should think. They are labeled "kenwood for audio".
I've got the bigs caps out, they are 10000uF 80V. Lots around for
about 20quid each, or some ebay ones which I try to avoid if possible.
Does this look OK ?http://connect-audio.co.uk/proddetai...000U80&cat=219
Does the life seem a bit short (I know this is at the max temp) ?

Also saw this but the lead spacing and layout is wrong:http://parts.digikey.co.uk/1/1/91787...ect-tha-series...

I did not realise the life was so limited though. I've left the amp on
24 hours a day on standby for years !

Also a couple of smaller 3300uF 50V jobs, I guess for a 5V or similar
supply for the ICs, DSP chips etc.
Probably worth changing those as well.

OR ..
Is this really worth my time and up to 50 quid fixing ???
A new replacement would cost 350 quid but would support blue ray
audio, HDMI etc.

Simon.


Electronic equipment is complex in terms of the number of possible
faults. Guessing is a poor repair strategy, especially when it costs
£50 a guess. Lytics normally last many decades, though there have been
some duds on the market causing problems.

The simplest way to test the caps is to measure the ripple on them
with the power on. If you dont have the proper equipment, you can use
a mmultimeter on ac volts setting, connecting it to the big cap via a
small 1uF non-polarised cap (ie polyester, not electrolytic). Once the
meter reading settles down from 80v or so, you should get a steady
reading of the ripple.

Its more likely to be something else than the caps.

PS what sort of amp would/could fail to support blueray?


NT

sm_jamieson wrote:
My approx 9 year old AV amp started buzzing / humming sounds like
100Hz, slowly got louder until drowning out the music ! PSU caps I
should think. They are labeled "kenwood for audio".
I've got the bigs caps out, they are 10000uF 80V. Lots around for
about 20quid each, or some ebay ones which I try to avoid if possible.
Does this look OK ?
http://connect-audio.co.uk/proddetai...000U80&cat=219
Does the life seem a bit short (I know this is at the max temp) ?

Also saw this but the lead spacing and layout is wrong:
http://parts.digikey.co.uk/1/1/91787...t1ka103fa.html

I did not realise the life was so limited though. I've left the amp on
24 hours a day on standby for years !

Also a couple of smaller 3300uF 50V jobs, I guess for a 5V or similar
supply for the ICs, DSP chips etc.
Probably worth changing those as well.

OR ..
Is this really worth my time and up to 50 quid fixing ???
A new replacement would cost 350 quid but would support blue ray
audio, HDMI etc.

Simon.

Seems overly expensive for reservoir caps.

Definitely worth fixing tho.

But you shouldn't be paying much more than a fiver..try fleabay.

Dave Plowman (News) wrote:
At that price I'd want to be certain it was those caps. Can you isolate
the main amps or perhaps short the inputs to be certain it isn't coming
from elsewhere?


Just solder a new 80v cap of almost any flavour over 1000uf across whats
there.


Identical issue in 50 year old valve radio. Fixed it.

I've got several amps here a lot older than that on the original smoothing
caps.


Bad caps abounded 7-10 years ago.

They all dried out..

Tabby wrote:
On Mar 3, 11:33 pm, sm_jamieson wrote:

My approx 9 year old AV amp started buzzing / humming sounds like
100Hz, slowly got louder until drowning out the music ! PSU caps I
should think. They are labeled "kenwood for audio".
I've got the bigs caps out, they are 10000uF 80V. Lots around for
about 20quid each, or some ebay ones which I try to avoid if possible.
Does this look OK ?http://connect-audio.co.uk/proddetai...000U80&cat=219
Does the life seem a bit short (I know this is at the max temp) ?

Also saw this but the lead spacing and layout is wrong:http://parts.digikey.co.uk/1/1/91787...ect-tha-series...

I did not realise the life was so limited though. I've left the amp on
24 hours a day on standby for years !

Also a couple of smaller 3300uF 50V jobs, I guess for a 5V or similar
supply for the ICs, DSP chips etc.
Probably worth changing those as well.

OR ..
Is this really worth my time and up to 50 quid fixing ???
A new replacement would cost 350 quid but would support blue ray
audio, HDMI etc.

Simon.


Electronic equipment is complex in terms of the number of possible
faults. Guessing is a poor repair strategy, especially when it costs
£50 a guess. Lytics normally last many decades, though there have been
some duds on the market causing problems.

The simplest way to test the caps is to measure the ripple on them
with the power on. If you dont have the proper equipment, you can use
a mmultimeter on ac volts setting, connecting it to the big cap via a
small 1uF non-polarised cap (ie polyester, not electrolytic). Once the
meter reading settles down from 80v or so, you should get a steady
reading of the ripple.

Its more likely to be something else than the caps.


It isn't.

Either a bad solder joint to the cap or the cap itself has gone high
resistance..but the classic 'it slowly gets worse' is almost 100% sure
to be the cap.

Easily tested by temporarily connecting something of adequate volatge
rating across it.

Caps are just about the only components that fail gradually and non
catastrophically.

Those and valves/CRT tubes.

Everything else tends to be either so low stress it lasts almost
indefinitely, or so high stress that it goes bang and the set goes dead.

On Mar 4, 4:37*am, The Natural Philosopher
wrote:
sm_jamieson wrote:
My approx 9 year old AV amp started buzzing / humming sounds like
100Hz, slowly got louder until drowning out the music ! PSU caps I
should think. They are labeled "kenwood for audio".
I've got the bigs caps out, they are 10000uF 80V. Lots around for
about 20quid each, or some ebay ones which I try to avoid if possible.
Does this look OK ?
http://connect-audio.co.uk/proddetai...000U80&cat=219
Does the life seem a bit short (I know this is at the max temp) ?

Also saw this but the lead spacing and layout is wrong:
http://parts.digikey.co.uk/1/1/91787...ect-tha-series...

I did not realise the life was so limited though. I've left the amp on
24 hours a day on standby for years !

Also a couple of smaller 3300uF 50V jobs, I guess for a 5V or similar
supply for the ICs, DSP chips etc.
Probably worth changing those as well.

OR ..
Is this really worth my time and up to 50 quid fixing ???
A new replacement would cost 350 quid but would support blue ray
audio, HDMI etc.

Simon.

Seems overly expensive *for reservoir caps.

Definitely worth fixing tho.

But you shouldn't be paying much more than a fiver..try fleabay.

There are some caps (more expensive) marked "for audio" etc.
Is this just marketing, or is there anything different ?
Surely in the power supply they cannot make much difference ?
I am sceptical myself.
Simon.

On Mar 4, 4:44*am, The Natural Philosopher
wrote:
Tabby wrote:
On Mar 3, 11:33 pm, sm_jamieson wrote:

My approx 9 year old AV amp started buzzing / humming sounds like
100Hz, slowly got louder until drowning out the music ! PSU caps I
should think. They are labeled "kenwood for audio".
I've got the bigs caps out, they are 10000uF 80V. Lots around for
about 20quid each, or some ebay ones which I try to avoid if possible.
Does this look OK ?http://connect-audio.co.uk/proddetai...000U80&cat=219
Does the life seem a bit short (I know this is at the max temp) ?

Also saw this but the lead spacing and layout is wrong:http://parts.digikey.co.uk/1/1/91787...ect-tha-series...

I did not realise the life was so limited though. I've left the amp on
24 hours a day on standby for years !

Also a couple of smaller 3300uF 50V jobs, I guess for a 5V or similar
supply for the ICs, DSP chips etc.
Probably worth changing those as well.

OR ..
Is this really worth my time and up to 50 quid fixing ???
A new replacement would cost 350 quid but would support blue ray
audio, HDMI etc.

Simon.

Electronic equipment is complex in terms of the number of possible
faults. Guessing is a poor repair strategy, especially when it costs
£50 a guess. Lytics normally last many decades, though there have been
some duds on the market causing problems.

The simplest way to test the caps is to measure the ripple on them
with the power on. If you dont have the proper equipment, you can use
a mmultimeter on ac volts setting, connecting it to the big cap via a
small 1uF non-polarised cap (ie polyester, not electrolytic). Once the
meter reading settles down from 80v or so, you should get a steady
reading of the ripple.

Its more likely to be something else than the caps.

It isn't.

Either a bad solder joint to the cap or the *cap itself has gone high
resistance..but the classic 'it slowly gets worse' is almost 100% sure
to be the cap.

Easily tested by temporarily connecting something of adequate volatge
rating across it.

The way the circuit boards are layed out with various daughter boards,
ribbon cables etc,
its very hard to have the circuit working and out of the case. I would
really have to change
the caps and put the whole thing back together to test it.
Simon.

On Thu, 3 Mar 2011 17:06:56 -0800 (PST), Tabby wrote:

PS what sort of amp would/could fail to support blueray?

One that doesn't have HDMI... A nine year old AV amp just predates
HDMI 1.0 which came out in Dec 2002.

A graceful failure into hum is almost certainly down to dead or dying
reservior capacitors.

80v is a bit of a odd rating, 63v or 100v are the normal ones.

CPC have:
CA05298 10kuF 100v £17.03
CA05334 10kuF 100v £15.01 "computer grade" higher ripple current
capability than the above.

--
Cheers
Dave.

sm_jamieson wrote:
On Mar 4, 4:37 am, The Natural Philosopher
wrote:
sm_jamieson wrote:
My approx 9 year old AV amp started buzzing / humming sounds like
100Hz, slowly got louder until drowning out the music ! PSU caps I
should think. They are labeled "kenwood for audio".
I've got the bigs caps out, they are 10000uF 80V. Lots around for
about 20quid each, or some ebay ones which I try to avoid if possible.
Does this look OK ?
http://connect-audio.co.uk/proddetai...000U80&cat=219
Does the life seem a bit short (I know this is at the max temp) ?
Also saw this but the lead spacing and layout is wrong:
http://parts.digikey.co.uk/1/1/91787...ect-tha-series...
I did not realise the life was so limited though. I've left the amp on
24 hours a day on standby for years !
Also a couple of smaller 3300uF 50V jobs, I guess for a 5V or similar
supply for the ICs, DSP chips etc.
Probably worth changing those as well.
OR ..
Is this really worth my time and up to 50 quid fixing ???
A new replacement would cost 350 quid but would support blue ray
audio, HDMI etc.
Simon.
Seems overly expensive for reservoir caps.

Definitely worth fixing tho.

But you shouldn't be paying much more than a fiver..try fleabay.

There are some caps (more expensive) marked "for audio" etc.
Is this just marketing, or is there anything different ?
Surely in the power supply they cannot make much difference ?
I am sceptical myself.

Because of the way they're made, electrolytics may have a significant
self inductance. I remember in the past buying low self inductance
versions for critical applications, which cost more.


--
Tciao for Now!

John.

Easily tested by temporarily connecting something of adequate volatge
rating across it.

The way the circuit boards are layed out with various daughter boards,
ribbon cables etc,
its very hard to have the circuit working and out of the case. I would
really have to change
the caps and put the whole thing back together to test it.
Simon.

Extend the leads from the replacement cap to the one inside the case for
test?..
--
Tony Sayer

In article
egroups.com, Archivist scribeth thus
Quote: Surely in the power supply they cannot make much difference ?
I am sceptical myself.

You're right to be sceptical of all 'golden ear" claims. However if you draw an
"equivalent" circuit of any amplifier, you will see that the power supply shows
as being in series with the load. In other words, the signal return from the
speaker goes through the power supply. This means that you should choose ps
components as carefully as you would for example speaker crossover components or
any other component in the signal path.
Two more points:
1. You don't need expensive caps, nor the exact capacitive value to test your
theory. Hang the cheapest on temporarily.
2. I personally wouldn't spend anything on equipment of that era...

J

Well you might want to re cap something like a QUAD 303 which is a very
worthwhile project around 30 40 odd quid for a replacement set..

We've got one here for a study setup, mainly plays audio off the PC
soundcard a much better external one that that usually fitted. Still
sounds fine ..



http://www.net-audio.co.uk/quad303caps.html
--
Tony Sayer

In article ,
tony sayer wrote:
Well you might want to re cap something like a QUAD 303 which is a very
worthwhile project around 30 40 odd quid for a replacement set..

We've got one here for a study setup, mainly plays audio off the PC
soundcard a much better external one that that usually fitted. Still
sounds fine ..

I'm using one to drive a pair of subs in the living room. It's never been
touched. Over 40 years old. ;-) No hum from it - although it's quite
possible it is out of spec in one way or another.

--
*A will is a dead giveaway*

Dave Plowman London SW
To e-mail, change noise into sound.

The Natural Philosopher wrote:
Dave Plowman (News) wrote:
At that price I'd want to be certain it was those caps. Can you
isolate the main amps or perhaps short the inputs to be certain it
isn't coming from elsewhere?


Just solder a new 80v cap of almost any flavour over 1000uf across
whats there.

Why would these need to be 80v out of interest? What sort of DC voltages do
these amps typically operate on? I know there's a margin for peaks, but 80v
across a nominal 8 ohm resistance would provide 800w. This is an amp, not a
room heater, surely?

On Mar 4, 9:30*am, "Dave Liquorice"
wrote:
On Thu, 3 Mar 2011 17:06:56 -0800 (PST), Tabby wrote:
PS what sort of amp would/could fail to support blueray?

One that doesn't have HDMI... A nine year old AV amp just predates
HDMI 1.0 which came out in Dec 2002.

A graceful failure into hum is almost certainly down to dead or dying
reservior capacitors.

80v is a bit of a odd rating, 63v or 100v are the normal ones.

CPC have:
CA05298 10kuF 100v £17.03
CA05334 10kuF 100v £15.01 "computer grade" higher ripple current
capability than the above.

Ouch. Others posts were suggesting I should be paying about a fiver !
Anway, I like the units ! "kuF" !
You should have quoted the price in deci-mega-pennies ;-)
Simon.

sm_jamieson wrote:
On Mar 4, 4:37 am, The Natural Philosopher
wrote:
sm_jamieson wrote:
My approx 9 year old AV amp started buzzing / humming sounds like
100Hz, slowly got louder until drowning out the music ! PSU caps I
should think. They are labeled "kenwood for audio".
I've got the bigs caps out, they are 10000uF 80V. Lots around for
about 20quid each, or some ebay ones which I try to avoid if possible.
Does this look OK ?
http://connect-audio.co.uk/proddetai...000U80&cat=219
Does the life seem a bit short (I know this is at the max temp) ?
Also saw this but the lead spacing and layout is wrong:
http://parts.digikey.co.uk/1/1/91787...ect-tha-series...
I did not realise the life was so limited though. I've left the amp on
24 hours a day on standby for years !
Also a couple of smaller 3300uF 50V jobs, I guess for a 5V or similar
supply for the ICs, DSP chips etc.
Probably worth changing those as well.
OR ..
Is this really worth my time and up to 50 quid fixing ???
A new replacement would cost 350 quid but would support blue ray
audio, HDMI etc.
Simon.
Seems overly expensive for reservoir caps.

Definitely worth fixing tho.

But you shouldn't be paying much more than a fiver..try fleabay.

There are some caps (more expensive) marked "for audio" etc.
Is this just marketing, or is there anything different ?
Surely in the power supply they cannot make much difference ?
I am sceptical myself.
Simon.
generally able to handle high peak currents and maintain low resistance.

John Williamson wrote:
sm_jamieson wrote:
On Mar 4, 4:37 am, The Natural Philosopher
wrote:
sm_jamieson wrote:
My approx 9 year old AV amp started buzzing / humming sounds like
100Hz, slowly got louder until drowning out the music ! PSU caps I
should think. They are labeled "kenwood for audio".
I've got the bigs caps out, they are 10000uF 80V. Lots around for
about 20quid each, or some ebay ones which I try to avoid if possible.
Does this look OK ?
http://connect-audio.co.uk/proddetai...000U80&cat=219
Does the life seem a bit short (I know this is at the max temp) ?
Also saw this but the lead spacing and layout is wrong:
http://parts.digikey.co.uk/1/1/91787...ect-tha-series...

I did not realise the life was so limited though. I've left the amp on
24 hours a day on standby for years !
Also a couple of smaller 3300uF 50V jobs, I guess for a 5V or similar
supply for the ICs, DSP chips etc.
Probably worth changing those as well.
OR ..
Is this really worth my time and up to 50 quid fixing ???
A new replacement would cost 350 quid but would support blue ray
audio, HDMI etc.
Simon.
Seems overly expensive for reservoir caps.

Definitely worth fixing tho.

But you shouldn't be paying much more than a fiver..try fleabay.

There are some caps (more expensive) marked "for audio" etc.
Is this just marketing, or is there anything different ?
Surely in the power supply they cannot make much difference ?
I am sceptical myself.

Because of the way they're made, electrolytics may have a significant
self inductance. I remember in the past buying low self inductance
versions for critical applications, which cost more.


No, low series resistance. If inductance is an issue, you put a smaller
cap across them.

That takes care of HF impedances.

On Mar 4, 10:32*am, tony sayer wrote:
Easily tested by temporarily connecting something of adequate volatge
rating across it.

The way the circuit boards are layed out with various daughter boards,
ribbon cables etc,
its very hard to have the circuit working and out of the case. I would
really have to change
the caps and put the whole thing back together to test it.
Simon.

Extend the leads from the replacement cap to the one inside the case for
test?..
--
Tony Sayer

I thought about something like that.
I'll probably solder in some type of connector so I can replace the
capacitors
easily from the front of the board. Then I can stick the existing one
back in temporarily and see if a small cheapy cap in parallel reduces
the hum
Simon.

In article , Dave Plowman (News)
scribeth thus
In article ,
tony sayer wrote:
Well you might want to re cap something like a QUAD 303 which is a very
worthwhile project around 30 40 odd quid for a replacement set..

We've got one here for a study setup, mainly plays audio off the PC
soundcard a much better external one that that usually fitted. Still
sounds fine ..

I'm using one to drive a pair of subs in the living room. It's never been
touched. Over 40 years old. ;-) No hum from it - although it's quite
possible it is out of spec in one way or another.


Sounds like an ideal candidate for an upgrade. Not only do you put new
caps in they have higher capacity the 2200 mfd goes to 4700 in the
series output, and now its 9400 mfd in the power supply but even the
small caps on the boards its worthwhile to change them too!...
--
Tony Sayer

On Mar 4, 11:09*am, "GB" wrote:
The Natural Philosopher wrote:
Dave Plowman (News) wrote:

Just solder a new 80v cap of almost any flavour over 1000uf across
whats there.

Why would these need to be 80v out of interest? What sort of DC voltages do
these amps typically operate on? I know there's a margin for peaks, but 80v
across a nominal *8 ohm resistance would provide 800w. This is an amp, not a
room heater, surely?

80 volts is the *peak* voltage, at the top of the waveform. The
wattage delivered to the speakers depends on the 'RMS' (root-mean-
square, a sort of average), which is 0.707, (for design purposes; it
varies with the waveform) of the peak.

In article ,
tony sayer wrote:
I'm using one to drive a pair of subs in the living room. It's never
been touched. Over 40 years old. ;-) No hum from it - although it's
quite possible it is out of spec in one way or another.


Sounds like an ideal candidate for an upgrade. Not only do you put new
caps in they have higher capacity the 2200 mfd goes to 4700 in the
series output, and now its 9400 mfd in the power supply but even the
small caps on the boards its worthwhile to change them too!...

If it ever goes wrong I'd consider that upgrade. But at the moment it does
its job adequately.

--
*Why do overlook and oversee mean opposite things?

Dave Plowman London SW
To e-mail, change noise into sound.

alexander.keys1 wrote:
On Mar 4, 11:09 am, "GB" wrote:
The Natural Philosopher wrote:
Dave Plowman (News) wrote:

Just solder a new 80v cap of almost any flavour over 1000uf across
whats there.

Why would these need to be 80v out of interest? What sort of DC
voltages do these amps typically operate on? I know there's a margin
for peaks, but 80v across a nominal 8 ohm resistance would provide
800w. This is an amp, not a room heater, surely?

80 volts is the *peak* voltage, at the top of the waveform. The
wattage delivered to the speakers depends on the 'RMS' (root-mean-
square, a sort of average), which is 0.707, (for design purposes; it
varies with the waveform) of the peak.

That's still 400w average power.



--
Murphy's ultimate law is that if something that could go wrong doesn't,
it turns out that it would have been better if it had gone wrong.

In article , GB
writes
alexander.keys1 wrote:
On Mar 4, 11:09 am, "GB" wrote:
The Natural Philosopher wrote:
Dave Plowman (News) wrote:

Just solder a new 80v cap of almost any flavour over 1000uf across
whats there.

Why would these need to be 80v out of interest? What sort of DC
voltages do these amps typically operate on? I know there's a margin
for peaks, but 80v across a nominal 8 ohm resistance would provide
800w. This is an amp, not a room heater, surely?

80 volts is the *peak* voltage, at the top of the waveform. The
wattage delivered to the speakers depends on the 'RMS' (root-mean-
square, a sort of average), which is 0.707, (for design purposes; it
varies with the waveform) of the peak.

That's still 400w average power.

There are life issues too, derate working voltage to 60 or 70% of spec
and they last 10x longer. Similar issues with temp, 105degC caps last
forever when derated.

Spec'd life at max temp and voltage on an electrolytic is rarely
impressive.
--
fred
FIVE TV's superbright logo - not the DOG's, it's ********

On Mar 4, 4:44*am, The Natural Philosopher
wrote:
Tabby wrote:
On Mar 3, 11:33 pm, sm_jamieson wrote:

My approx 9 year old AV amp started buzzing / humming sounds like
100Hz, slowly got louder until drowning out the music ! PSU caps I
should think. They are labeled "kenwood for audio".
I've got the bigs caps out, they are 10000uF 80V. Lots around for
about 20quid each, or some ebay ones which I try to avoid if possible.
Does this look OK ?http://connect-audio.co.uk/proddetai...000U80&cat=219
Does the life seem a bit short (I know this is at the max temp) ?

Also saw this but the lead spacing and layout is wrong:http://parts.digikey.co.uk/1/1/91787...ect-tha-series...

I did not realise the life was so limited though. I've left the amp on
24 hours a day on standby for years !

Also a couple of smaller 3300uF 50V jobs, I guess for a 5V or similar
supply for the ICs, DSP chips etc.
Probably worth changing those as well.

OR ..
Is this really worth my time and up to 50 quid fixing ???
A new replacement would cost 350 quid but would support blue ray
audio, HDMI etc.

Simon.

Electronic equipment is complex in terms of the number of possible
faults. Guessing is a poor repair strategy, especially when it costs
£50 a guess. Lytics normally last many decades, though there have been
some duds on the market causing problems.

The simplest way to test the caps is to measure the ripple on them
with the power on. If you dont have the proper equipment, you can use
a mmultimeter on ac volts setting, connecting it to the big cap via a
small 1uF non-polarised cap (ie polyester, not electrolytic). Once the
meter reading settles down from 80v or so, you should get a steady
reading of the ripple.

Its more likely to be something else than the caps.

It isn't.

Either a bad solder joint to the cap or the *cap itself has gone high
resistance..but the classic 'it slowly gets worse' is almost 100% sure
to be the cap.

Easily tested by temporarily connecting something of adequate volatge
rating across it.

Caps are just about the only components that fail gradually and non
catastrophically.

Those and valves/CRT tubes.

Everything else tends to be either so low stress it lasts almost
indefinitely, or so high stress that it goes bang and the set goes dead.

foolish strategy.

On Mar 4, 9:30*am, "Dave Liquorice"
wrote:
On Thu, 3 Mar 2011 17:06:56 -0800 (PST), Tabby wrote:
PS what sort of amp would/could fail to support blueray?

One that doesn't have HDMI... A nine year old AV amp just predates
HDMI 1.0 which came out in Dec 2002.


I see HDMI doesnt contain analogue output :/ Trouble with using
hardware to keep up with digital standards is they keep changing.

NT

In article , GB
wrote:
alexander.keys1 wrote:
On Mar 4, 11:09 am, "GB" wrote:
The Natural Philosopher wrote:
Dave Plowman (News) wrote:

Just solder a new 80v cap of almost any flavour over 1000uf across
whats there.

Why would these need to be 80v out of interest? What sort of DC
voltages do these amps typically operate on? I know there's a margin
for peaks, but 80v across a nominal 8 ohm resistance would provide
800w. This is an amp, not a room heater, surely?

80 volts is the *peak* voltage, at the top of the waveform. The
wattage delivered to the speakers depends on the 'RMS' (root-mean-
square, a sort of average), which is 0.707, (for design purposes; it
varies with the waveform) of the peak.

Actually for a sine wave the mean power is half the peak power. It is the
voltages that are in the ratio of 1/root(2).

That's still 400w average power.

Not seen the initial postings in this thread as it has only just started
being xposted to uk.rec.audio. However, the above depends on details like
if the amp is single-rail or dual-rail.

For example, for 100wpc (mean for sinewave) into 8 Ohms you'd need +/- 40V
rails as absolute minimum in a dual-rail design. If it were a single rail
then you'd need 0V and a 80V rail as absolute minimum. In practice a
real-world design would need headroom to drive the devices, so 0 - 80V
single rail would get you somewhat less than 100 wpc (sinewave mean). Then
if you also take into account that the PSU will probably 'sag' under
sustained load you'd find that 80V single rail would be much less when you
are trying to get sustained sinewave power from both channels of a stereo
amp.

So in practice you might find that 0 - 80V single rail ended up giving you
far less than 100wpc mean sinewave stereo. (Although peak levels for music
could be somewhat higher.)

And as I see someone else has pointed out. You also would be safest
choosing a cap whose spec voltage was well above the actual rail voltage
when the amp isn't sagging the voltage. Hence an 80V cap would be sensible
for use with a somewhat lower rail voltage.

Slainte,

Jim

--
Please use the address on the audiomisc page if you wish to email me.
Electronics http://www.st-and.ac.uk/~www_pa/Scot...o/electron.htm
Armstrong Audio http://www.audiomisc.co.uk/Armstrong/armstrong.html
Audio Misc http://www.audiomisc.co.uk/index.html

GB wrote:
alexander.keys1 wrote:
On Mar 4, 11:09 am, "GB" wrote:
The Natural Philosopher wrote:
Dave Plowman (News) wrote:
Just solder a new 80v cap of almost any flavour over 1000uf across
whats there.
Why would these need to be 80v out of interest? What sort of DC
voltages do these amps typically operate on? I know there's a margin
for peaks, but 80v across a nominal 8 ohm resistance would provide
800w. This is an amp, not a room heater, surely?
80 volts is the *peak* voltage, at the top of the waveform. The
wattage delivered to the speakers depends on the 'RMS' (root-mean-
square, a sort of average), which is 0.707, (for design purposes; it
varies with the waveform) of the peak.

That's still 400w average power.


only with a split rail supply.

Otherwise its about - with PSU sag and a safety margin the square root
of two times half the voltage minus about 15v, so 24v rms Or in power
terms about 132W into 4 ohms

Unless its split rail with two 80V caps, or an H bridge..in which case
yes, its abut 400W.

Tabby wrote:
On Mar 4, 4:44 am, The Natural Philosopher
wrote:
Tabby wrote:
On Mar 3, 11:33 pm, sm_jamieson wrote:
My approx 9 year old AV amp started buzzing / humming sounds like
100Hz, slowly got louder until drowning out the music ! PSU caps I
should think. They are labeled "kenwood for audio".
I've got the bigs caps out, they are 10000uF 80V. Lots around for
about 20quid each, or some ebay ones which I try to avoid if possible.
Does this look OK ?http://connect-audio.co.uk/proddetai...000U80&cat=219
Does the life seem a bit short (I know this is at the max temp) ?
Also saw this but the lead spacing and layout is wrong:http://parts.digikey.co.uk/1/1/91787...ect-tha-series...
I did not realise the life was so limited though. I've left the amp on
24 hours a day on standby for years !
Also a couple of smaller 3300uF 50V jobs, I guess for a 5V or similar
supply for the ICs, DSP chips etc.
Probably worth changing those as well.
OR ..
Is this really worth my time and up to 50 quid fixing ???
A new replacement would cost 350 quid but would support blue ray
audio, HDMI etc.
Simon.
Electronic equipment is complex in terms of the number of possible
faults. Guessing is a poor repair strategy, especially when it costs
£50 a guess. Lytics normally last many decades, though there have been
some duds on the market causing problems.
The simplest way to test the caps is to measure the ripple on them
with the power on. If you dont have the proper equipment, you can use
a mmultimeter on ac volts setting, connecting it to the big cap via a
small 1uF non-polarised cap (ie polyester, not electrolytic). Once the
meter reading settles down from 80v or so, you should get a steady
reading of the ripple.
Its more likely to be something else than the caps.
It isn't.

Either a bad solder joint to the cap or the cap itself has gone high
resistance..but the classic 'it slowly gets worse' is almost 100% sure
to be the cap.

Easily tested by temporarily connecting something of adequate volatge
rating across it.

Caps are just about the only components that fail gradually and non
catastrophically.

Those and valves/CRT tubes.

Everything else tends to be either so low stress it lasts almost
indefinitely, or so high stress that it goes bang and the set goes dead.

foolish strategy.


Oh dear. I guess the 16 years i spent designed audio power amps was
completely wasted?

On 04/03/2011 11:09, GB wrote:
The Natural Philosopher wrote:
Dave Plowman (News) wrote:
At that price I'd want to be certain it was those caps. Can you
isolate the main amps or perhaps short the inputs to be certain it
isn't coming from elsewhere?


Just solder a new 80v cap of almost any flavour over 1000uf across
whats there.

Why would these need to be 80v out of interest? What sort of DC voltages do
these amps typically operate on? I know there's a margin for peaks, but 80v
across a nominal 8 ohm resistance would provide 800w. This is an amp, not a
room heater, surely?



Fairly ordinary domestic power amps run with +/- 40 or 50 v rails.
80v rated caps would not be unreasonable.

The full rail voltage won't appear on the output ( unless the one of the
Output Devices have gone S/C ).


--
Ron

On Mar 4, 3:22*pm, The Natural Philosopher
wrote:
Tabby wrote:
On Mar 4, 4:44 am, The Natural Philosopher
wrote:
Tabby wrote:
On Mar 3, 11:33 pm, sm_jamieson wrote:
My approx 9 year old AV amp started buzzing / humming sounds like
100Hz, slowly got louder until drowning out the music ! PSU caps I
should think. They are labeled "kenwood for audio".
I've got the bigs caps out, they are 10000uF 80V. Lots around for
about 20quid each, or some ebay ones which I try to avoid if possible.
Does this look OK ?http://connect-audio.co.uk/proddetai...000U80&cat=219
Does the life seem a bit short (I know this is at the max temp) ?
Also saw this but the lead spacing and layout is wrong:http://parts.digikey.co.uk/1/1/91787...ect-tha-series...
I did not realise the life was so limited though. I've left the amp on
24 hours a day on standby for years !
Also a couple of smaller 3300uF 50V jobs, I guess for a 5V or similar
supply for the ICs, DSP chips etc.
Probably worth changing those as well.
OR ..
Is this really worth my time and up to 50 quid fixing ???
A new replacement would cost 350 quid but would support blue ray
audio, HDMI etc.
Simon.
Electronic equipment is complex in terms of the number of possible
faults. Guessing is a poor repair strategy, especially when it costs
£50 a guess. Lytics normally last many decades, though there have been
some duds on the market causing problems.
The simplest way to test the caps is to measure the ripple on them
with the power on. If you dont have the proper equipment, you can use
a mmultimeter on ac volts setting, connecting it to the big cap via a
small 1uF non-polarised cap (ie polyester, not electrolytic). Once the
meter reading settles down from 80v or so, you should get a steady
reading of the ripple.
Its more likely to be something else than the caps.
It isn't.

Either a bad solder joint to the cap or the *cap itself has gone high
resistance..but the classic 'it slowly gets worse' is almost 100% sure
to be the cap.

Easily tested by temporarily connecting something of adequate volatge
rating across it.

Caps are just about the only components that fail gradually and non
catastrophically.

Those and valves/CRT tubes.

Everything else tends to be either so low stress it lasts almost
indefinitely, or so high stress that it goes bang and the set goes dead.

foolish strategy.

Oh dear. I guess the 16 years i spent designed audio power amps was
completely wasted?

Youre fond of asuming too much

"fred"

There are life issues too, derate working voltage to 60 or 70% of spec and
they last 10x longer.

** That is complete nonsense.

Electro life is not related to DC operating voltage, unless the rated limit
is exceeded then it is VERY short.


Similar issues with temp, 105degC caps last forever when derated.


** Also complete nonsense - there is little increase in expected life
using 105C types unless the local ambient is over 75C.

Electro lifespan is all about the quality of the airtight seal in the end of
the cap - cos the end of life occurs when most of the electrolyte has
escaped as vapour through an imperfect seal. The rate of loss of electrolyte
is a function of the local ambient temperature and ripple current ( if any)
heating the electro.

105C types can operate at higher temps, that is their only advantage.

Long life electros come in both 85C and 105 C types - all that is different
is the quality of that seal.



...... Phil

"The Natural Philosopher"

Unless its split rail with two 80V caps, or an H bridge..in which case
yes, its abut 400W.

** That is a bit optimistic.

1. If the filter electros are each rated at 80VDC working and one sensibly
allows for higher than nominal AC supply - then the *unloaded* DC rails are
likely to be +/- 74 volts.

2. If the AC tranny is of conventional design ( toroidal or E-core) then the
regulation factor is such that the average DC rail will drop under load by
about 12%.

3. If the capacitance is a typical value like 6800uF for one channel - then
the p-p ripple voltage under steady load is about 4 volts - more if the
audio test frequency is under 100 Hz.

4. An output stage is never able to swing to the full extent of the
available DC rail voltage - particularly so if the output devices are
lateral mosfets. Assuming a typical complementary Darlington output stage
with emitters supplying the load - the output can swing within about 5 volts
of the available supply with an 8 ohm load.

Adding this up we have:

74 - 9 - 2 - 5 = 58 volts peak.

So the "rms" power on sine wave into 8 ohms will be 210 watts.




...... Phil

Phil Allison wrote:
"The Natural Philosopher"
Unless its split rail with two 80V caps, or an H bridge..in which case
yes, its abut 400W.

** That is a bit optimistic.

1. If the filter electros are each rated at 80VDC working and one sensibly
allows for higher than nominal AC supply - then the *unloaded* DC rails are
likely to be +/- 74 volts.

2. If the AC tranny is of conventional design ( toroidal or E-core) then the
regulation factor is such that the average DC rail will drop under load by
about 12%.

3. If the capacitance is a typical value like 6800uF for one channel - then
the p-p ripple voltage under steady load is about 4 volts - more if the
audio test frequency is under 100 Hz.

4. An output stage is never able to swing to the full extent of the
available DC rail voltage - particularly so if the output devices are
lateral mosfets. Assuming a typical complementary Darlington output stage
with emitters supplying the load - the output can swing within about 5 volts
of the available supply with an 8 ohm load.

Adding this up we have:

74 - 9 - 2 - 5 = 58 volts peak.

No. 58 volts peak TO peak.


So the "rms" power on sine wave into 8 ohms will be 210 watts.

No, slightly over 50W.





..... Phil

The Natural Philosopher wrote:
Phil Allison wrote:
"The Natural Philosopher"
Unless its split rail with two 80V caps, or an H bridge..in which
case yes, its abut 400W.

** That is a bit optimistic.

1. If the filter electros are each rated at 80VDC working and one
sensibly allows for higher than nominal AC supply - then the
*unloaded* DC rails are likely to be +/- 74 volts.

2. If the AC tranny is of conventional design ( toroidal or E-core)
then the regulation factor is such that the average DC rail will drop
under load by about 12%.

3. If the capacitance is a typical value like 6800uF for one channel
- then the p-p ripple voltage under steady load is about 4 volts -
more if the audio test frequency is under 100 Hz.

4. An output stage is never able to swing to the full extent of the
available DC rail voltage - particularly so if the output devices are
lateral mosfets. Assuming a typical complementary Darlington output
stage with emitters supplying the load - the output can swing within
about 5 volts of the available supply with an 8 ohm load.

Adding this up we have:

74 - 9 - 2 - 5 = 58 volts peak.

No. 58 volts peak TO peak.


So the "rms" power on sine wave into 8 ohms will be 210 watts.

No, slightly over 50W.


Ok I see you are talking about split rails. I read the above too
quickly. I don't think the OP mentioned that he had split rails.

So your analysis is correct for what equates to a +-60V supply.

However I have yet to see that sort of power and arrangement outside
some pro audio kit.The semiconductor cost is pretty high above 100V.






..... Phil

John Rumm wrote:
On 04/03/2011 08:55, sm_jamieson wrote:

There are some caps (more expensive) marked "for audio" etc.
Is this just marketing, or is there anything different ?
Surely in the power supply they cannot make much difference ?
I am sceptical myself.

When you think that an amplifier is in its simplest analysis a voltage
(or current) modulated variable output power supply, you appreciate the
PSU is a fairly critical part that is actually in circuit with the load.

Fairly NON critical part actually. Since the feedback that controls the
output is taken from across the load, not the power supply.

That is the trouble with 'simplest analyses'..

On 03/03/2011 23:33, sm_jamieson wrote:
My approx 9 year old AV amp started buzzing / humming sounds like
100Hz, slowly got louder until drowning out the music ! PSU caps I
should think. They are labeled "kenwood for audio".
I've got the bigs caps out,

Is there the same racket coming out of the tape monitor output?

--
Adrian C

On Mar 5, 7:05*pm, Adrian C wrote:
On 03/03/2011 23:33, sm_jamieson wrote:

My approx 9 year old AV amp started buzzing / humming sounds like
100Hz, slowly got louder until drowning out the music ! PSU caps I
should think. They are labeled "kenwood for audio".
I've got the bigs caps out,

Is there the same racket coming out of the tape monitor output?


Good point. i.e. without the power output stages. Didn't think to
check that.
Well, I'm going to put trailing leads in the PCB where the caps were
and put the thing back together.
Then I can experiment to check it is the caps. Then I'll leave any new
caps on the
end of short trailing leads and wedge them in place somehow.
I'll let y'all know how it goes.
Simon.

"The Natural Philosopher"

Unless its split rail with two 80V caps, or an H bridge..in which case
yes, its abut 400W.


** Can you read your own words ??


..... Phil

John Rumm wrote:
On 05/03/2011 16:28, The Natural Philosopher wrote:
John Rumm wrote:
On 04/03/2011 08:55, sm_jamieson wrote:

There are some caps (more expensive) marked "for audio" etc.
Is this just marketing, or is there anything different ?
Surely in the power supply they cannot make much difference ?
I am sceptical myself.

When you think that an amplifier is in its simplest analysis a voltage
(or current) modulated variable output power supply, you appreciate
the PSU is a fairly critical part that is actually in circuit with the
load.

Fairly NON critical part actually. Since the feedback that controls the
output is taken from across the load, not the power supply.

While true, the key point remains; you are better off not allowing
excess PSU generated noise through to the output in the first place than
you are attempting to compensate for it later.




Smplistic exaplanatin: A voltage regulator is an audio amplifier
configured to have zero AC input and a precise DC output :-)

I.e it makes little difference where you put your supply ripple
rejection. Its the same amount of componentry.

It s not hard to ensure that the supply rail rejection of an audio
amplifier even before feedback is applied is well up in the 80-100dB
range: Adding feedback takes it to the completely inaudible.

To think otherwise is to be beguiled by HiFi Bull**** merchants.

Remember, when te music stops, so does the current drain on a class B
amp. There is bugger all ripple to break through.

Under power, the music is so damned loud you wont hear any hum
breakthrough that's 100dB down on the signal anyway.

The only time you hear it is if its faulty, or you are clipping to it.

Or in terms of odd harmonic distortion if there is resistance in it and
your supply rejection is crap. But as I said, supply rejection is one of
the things that is relatively easy to get very very good . Constant
current balanced pair phase splitters.. even cascaded transistors remove
miller effects from the high voltage swing transistors..Christ even the
'all on a chip' power amps have all that.

The proof of the pudding is in the final distortion products you achieve
at highish powers. .