I have a couple of 20 Amp linear DC power supplies with hot transformers.

With no load, one gets up to 115 Degrees F after several hours. The
other gets up to 125 Degrees F. Measurements were made with an IR
thermometer looking at the top of the transformer. I disconnected the
secondary windings of one, but results were the same.

With their covers installed, neither power supply feels excessively hot.
The one that got to 125, gets to 95 Degrees F on top of its cover with
about two Amps load.

One cause might be not enough iron in the core. I suppose there could
be some circulating currents in the core as well. Regardless, does
anyone know if they are hot enough to be a problem? Or should I just
not worry about it?

I checked several other power supplies, and none had transformers above
95 Degrees F.

Fred

On Mon, 21 Jul 2014 11:18:07 -0700, Fred McKenzie wrote:

I have a couple of 20 Amp linear DC power supplies with hot transformers.

With no load, one gets up to 115 Degrees F after several hours. The
other gets up to 125 Degrees F. Measurements were made with an IR
thermometer looking at the top of the transformer. I disconnected the
secondary windings of one, but results were the same.

With their covers installed, neither power supply feels excessively hot.
The one that got to 125, gets to 95 Degrees F on top of its cover with
about two Amps load.

One cause might be not enough iron in the core. I suppose there could
be some circulating currents in the core as well. Regardless, does
anyone know if they are hot enough to be a problem? Or should I just
not worry about it?

I checked several other power supplies, and none had transformers above
95 Degrees F.

Fred

46C? and 50C no biggie

transformers are passive devices and made out of 'material'

easily take 65C, that's 150F

you may be running your AC mains at 125Vac instead of the 115Vac, which
will make them run just that bit hotter to where you noticed.

On 22/07/2014 4:18 AM, Fred McKenzie wrote:
I have a couple of 20 Amp linear DC power supplies with hot transformers.

With no load, one gets up to 115 Degrees F after several hours. The
other gets up to 125 Degrees F. Measurements were made with an IR
thermometer looking at the top of the transformer. I disconnected the
secondary windings of one, but results were the same.

With their covers installed, neither power supply feels excessively hot.
The one that got to 125, gets to 95 Degrees F on top of its cover with
about two Amps load.

One cause might be not enough iron in the core. I suppose there could
be some circulating currents in the core as well. Regardless, does
anyone know if they are hot enough to be a problem? Or should I just
not worry about it?

I checked several other power supplies, and none had transformers above
95 Degrees F.

Fred


**Most power transformers will operate at 100 degrees C quite safely,
though I prefer to see less than 75 C. I have no idea what 125 degrees F
is and I have no interest either, but I suspect it is less than 75 C.

[ASIDE] This is an international group. Almost none of the planet's
population (less than 5%) bothers with archane measurements, like
degrees F, anymore. Please learn the Metric system.

--
Trevor Wilson www.rageaudio.com.au

"Trevor Wilson" wrote in message
...
On 22/07/2014 4:18 AM, Fred McKenzie wrote:
I have a couple of 20 Amp linear DC power supplies with hot transformers.

With no load, one gets up to 115 Degrees F after several hours. The
other gets up to 125 Degrees F. Measurements were made with an IR
thermometer looking at the top of the transformer. I disconnected the
secondary windings of one, but results were the same.

With their covers installed, neither power supply feels excessively hot.
The one that got to 125, gets to 95 Degrees F on top of its cover with
about two Amps load.

One cause might be not enough iron in the core. I suppose there could
be some circulating currents in the core as well. Regardless, does
anyone know if they are hot enough to be a problem? Or should I just
not worry about it?

I checked several other power supplies, and none had transformers above
95 Degrees F.

Fred


**Most power transformers will operate at 100 degrees C quite safely,
though I prefer to see less than 75 C. I have no idea what 125 degrees F
is and I have no interest either, but I suspect it is less than 75 C.

[ASIDE] This is an international group. Almost none of the planet's
population (less than 5%) bothers with archane measurements, like degrees
F, anymore. Please learn the Metric system.

--
Trevor Wilson www.rapeaudio.com.au


Why, because you are too ****ing stupid or lazy to do a simple conversion?

So why did you even take the time to make your stupid comments?

"Tom Miller" wrote in message ...


"Trevor Wilson" wrote in message
...
On 22/07/2014 4:18 AM, Fred McKenzie wrote:
I have a couple of 20 Amp linear DC power supplies with hot transformers.

With no load, one gets up to 115 Degrees F after several hours. The
other gets up to 125 Degrees F. Measurements were made with an IR
thermometer looking at the top of the transformer. I disconnected the
secondary windings of one, but results were the same.

With their covers installed, neither power supply feels excessively hot.
The one that got to 125, gets to 95 Degrees F on top of its cover with
about two Amps load.

One cause might be not enough iron in the core. I suppose there could
be some circulating currents in the core as well. Regardless, does
anyone know if they are hot enough to be a problem? Or should I just
not worry about it?

I checked several other power supplies, and none had transformers above
95 Degrees F.

Fred


**Most power transformers will operate at 100 degrees C quite safely,
though I prefer to see less than 75 C. I have no idea what 125 degrees F
is and I have no interest either, but I suspect it is less than 75 C.

[ASIDE] This is an international group. Almost none of the planet's
population (less than 5%) bothers with archane measurements, like degrees
F, anymore. Please learn the Metric system.

--
Trevor Wilson www.rapeaudio.com.au


Why, because you are too ****ing stupid or lazy to do a simple conversion?




OK, convert the very accurate and reproducable measurement of 62.25cm, to
the Imperial system, and you get 24inches and 39/64ths.

That's a bit of a joke, surely, that should not be present in the 21st
century.


Gareth.

Gareth Magennis laid this down on his screen :

"Tom Miller" wrote in message ...


"Trevor Wilson" wrote in message
...
On 22/07/2014 4:18 AM, Fred McKenzie wrote:
I have a couple of 20 Amp linear DC power supplies with hot transformers.

With no load, one gets up to 115 Degrees F after several hours. The
other gets up to 125 Degrees F. Measurements were made with an IR
thermometer looking at the top of the transformer. I disconnected the
secondary windings of one, but results were the same.

With their covers installed, neither power supply feels excessively hot.
The one that got to 125, gets to 95 Degrees F on top of its cover with
about two Amps load.

One cause might be not enough iron in the core. I suppose there could
be some circulating currents in the core as well. Regardless, does
anyone know if they are hot enough to be a problem? Or should I just
not worry about it?

I checked several other power supplies, and none had transformers above
95 Degrees F.

Fred


**Most power transformers will operate at 100 degrees C quite safely,
though I prefer to see less than 75 C. I have no idea what 125 degrees F is
and I have no interest either, but I suspect it is less than 75 C.

[ASIDE] This is an international group. Almost none of the planet's
population (less than 5%) bothers with archane measurements, like degrees
F, anymore. Please learn the Metric system.

-- Trevor Wilson www.rapeaudio.com.au


Why, because you are too ****ing stupid or lazy to do a simple conversion?




OK, convert the very accurate and reproducable measurement of 62.25cm, to the
Imperial system, and you get 24inches and 39/64ths.

That's a bit of a joke, surely, that should not be present in the 21st
century.


Gareth.

No it converts to 24.507874 inches if you us the same maths notation.

"Gareth Magennis" wrote in message
...


"Tom Miller" wrote in message ...


"Trevor Wilson" wrote in message
...
On 22/07/2014 4:18 AM, Fred McKenzie wrote:
I have a couple of 20 Amp linear DC power supplies with hot
transformers.

With no load, one gets up to 115 Degrees F after several hours. The
other gets up to 125 Degrees F. Measurements were made with an IR
thermometer looking at the top of the transformer. I disconnected the
secondary windings of one, but results were the same.

With their covers installed, neither power supply feels excessively hot.
The one that got to 125, gets to 95 Degrees F on top of its cover with
about two Amps load.

One cause might be not enough iron in the core. I suppose there could
be some circulating currents in the core as well. Regardless, does
anyone know if they are hot enough to be a problem? Or should I just
not worry about it?

I checked several other power supplies, and none had transformers above
95 Degrees F.

Fred


**Most power transformers will operate at 100 degrees C quite safely,
though I prefer to see less than 75 C. I have no idea what 125 degrees F
is and I have no interest either, but I suspect it is less than 75 C.

[ASIDE] This is an international group. Almost none of the planet's
population (less than 5%) bothers with archane measurements, like degrees
F, anymore. Please learn the Metric system.

--
Trevor Wilson www.rapeaudio.com.au


Why, because you are too ****ing stupid or lazy to do a simple conversion?




OK, convert the very accurate and reproducable measurement of 62.25cm, to
the Imperial system, and you get 24inches and 39/64ths.

That's a bit of a joke, surely, that should not be present in the 21st
century.


Gareth.

Why not use 24.50 inches? Minding the significant figures.
It only bothers lazy people. But at least stay within one system.

Then there's pounds, shillings, pence, etc. Oh, at least you have the Euro.

"RobertMacy" wrote in message
newsp.xjc24hpo2cx0wh@ajm...
On Mon, 21 Jul 2014 11:18:07 -0700, Fred McKenzie wrote:

I have a couple of 20 Amp linear DC power supplies with hot transformers.

With no load, one gets up to 115 Degrees F after several hours. The
other gets up to 125 Degrees F. Measurements were made with an IR
thermometer looking at the top of the transformer. I disconnected the
secondary windings of one, but results were the same.

With their covers installed, neither power supply feels excessively hot.
The one that got to 125, gets to 95 Degrees F on top of its cover with
about two Amps load.

One cause might be not enough iron in the core. I suppose there could
be some circulating currents in the core as well. Regardless, does
anyone know if they are hot enough to be a problem? Or should I just
not worry about it?

I checked several other power supplies, and none had transformers above
95 Degrees F.

Fred

46C? and 50C no biggie

transformers are passive devices and made out of 'material'

easily take 65C, that's 150F

you may be running your AC mains at 125Vac instead of the 115Vac, which
will make them run just that bit hotter to where you noticed.


One thing the OP failed to state is the voltage of his 20 amp power supply.
2000 volts at 20 amps is a much larger transformer then one might find in a
12 volt, 20 amp supply.

Trevor Wilson was thinking very hard :
On 22/07/2014 4:18 AM, Fred McKenzie wrote:
I have a couple of 20 Amp linear DC power supplies with hot transformers.

With no load, one gets up to 115 Degrees F after several hours. The
other gets up to 125 Degrees F. Measurements were made with an IR
thermometer looking at the top of the transformer. I disconnected the
secondary windings of one, but results were the same.

With their covers installed, neither power supply feels excessively hot.
The one that got to 125, gets to 95 Degrees F on top of its cover with
about two Amps load.

One cause might be not enough iron in the core. I suppose there could
be some circulating currents in the core as well. Regardless, does
anyone know if they are hot enough to be a problem? Or should I just
not worry about it?

I checked several other power supplies, and none had transformers above
95 Degrees F.

Fred


**Most power transformers will operate at 100 degrees C quite safely, though
I prefer to see less than 75 C. I have no idea what 125 degrees F is and I
have no interest either, but I suspect it is less than 75 C.

[ASIDE] This is an international group. Almost none of the planet's
population (less than 5%) bothers with archane measurements, like degrees F,
anymore. Please learn the Metric system.

Actually it is 51.66 deg C which is not to hard to figure and afterall
most of us down here have learnt over the years to cope with whatever
the underdeveloped world chooses to use. :-?

"John G" wrote in message
. au...

Gareth Magennis laid this down on his screen :

"Tom Miller" wrote in message ...


"Trevor Wilson" wrote in message
...
On 22/07/2014 4:18 AM, Fred McKenzie wrote:
I have a couple of 20 Amp linear DC power supplies with hot
transformers.

With no load, one gets up to 115 Degrees F after several hours. The
other gets up to 125 Degrees F. Measurements were made with an IR
thermometer looking at the top of the transformer. I disconnected the
secondary windings of one, but results were the same.

With their covers installed, neither power supply feels excessively hot.
The one that got to 125, gets to 95 Degrees F on top of its cover with
about two Amps load.

One cause might be not enough iron in the core. I suppose there could
be some circulating currents in the core as well. Regardless, does
anyone know if they are hot enough to be a problem? Or should I just
not worry about it?

I checked several other power supplies, and none had transformers above
95 Degrees F.

Fred


**Most power transformers will operate at 100 degrees C quite safely,
though I prefer to see less than 75 C. I have no idea what 125 degrees F
is and I have no interest either, but I suspect it is less than 75 C.

[ASIDE] This is an international group. Almost none of the planet's
population (less than 5%) bothers with archane measurements, like degrees
F, anymore. Please learn the Metric system.

-- Trevor Wilson www.rapeaudio.com.au


Why, because you are too ****ing stupid or lazy to do a simple conversion?




OK, convert the very accurate and reproducable measurement of 62.25cm, to
the Imperial system, and you get 24inches and 39/64ths.

That's a bit of a joke, surely, that should not be present in the 21st
century.


Gareth.

No it converts to 24.507874 inches if you us the same maths notation.




The point is that the Imperial system commonly uses discrete steps that are
only accurate to those steps.

The metric system does not suffer this limitation.


Gareth.

It happens that Gareth Magennis formulated :

"John G" wrote in message
. au...

Gareth Magennis laid this down on his screen :

"Tom Miller" wrote in message ...


"Trevor Wilson" wrote in message
...
On 22/07/2014 4:18 AM, Fred McKenzie wrote:
I have a couple of 20 Amp linear DC power supplies with hot transformers.

With no load, one gets up to 115 Degrees F after several hours. The
other gets up to 125 Degrees F. Measurements were made with an IR
thermometer looking at the top of the transformer. I disconnected the
secondary windings of one, but results were the same.

With their covers installed, neither power supply feels excessively hot.
The one that got to 125, gets to 95 Degrees F on top of its cover with
about two Amps load.

One cause might be not enough iron in the core. I suppose there could
be some circulating currents in the core as well. Regardless, does
anyone know if they are hot enough to be a problem? Or should I just
not worry about it?

I checked several other power supplies, and none had transformers above
95 Degrees F.

Fred


**Most power transformers will operate at 100 degrees C quite safely,
though I prefer to see less than 75 C. I have no idea what 125 degrees F
is and I have no interest either, but I suspect it is less than 75 C.

[ASIDE] This is an international group. Almost none of the planet's
population (less than 5%) bothers with archane measurements, like degrees
F, anymore. Please learn the Metric system.

-- Trevor Wilson www.rapeaudio.com.au


Why, because you are too ****ing stupid or lazy to do a simple conversion?




OK, convert the very accurate and reproducable measurement of 62.25cm, to
the Imperial system, and you get 24inches and 39/64ths.

That's a bit of a joke, surely, that should not be present in the 21st
century.


Gareth.

No it converts to 24.507874 inches if you us the same maths notation.




The point is that the Imperial system commonly uses discrete steps that are
only accurate to those steps.

The metric system does not suffer this limitation.


Gareth.

Neither does the imperial system if you use a rule marked in tenths and
Micrometers are marked in 1/1000s or some such and not fractions which
were near enough for woodworkers in the past.

PS I am no fan of Imperial either in measurement or in Government but
we have to live with rest of the world and be tolerant of whatever
comes by. :-Z

**Most power transformers will operate at 100 degrees C quite safely,
though I prefer to see less than 75 C. I have no idea what 125 degrees F is
and I have no interest either, but I suspect it is less than 75 C.

It's such a big deal to convert, isn't it?

Start by subtracting 32. That's 93, which you can round off to 90. Then take
5/9 of that -- 50, which is close enough. You can do it in your head in a few
seconds.

There's no need to memorize the formula, if you remember that 0 and 32 degrees
are the same point, and 1 degree F is 9/5 degree C.


[ASIDE] This is an international group. Almost none of the planet's
population (less than 5%) bothers with archane measurements,
like degrees F, anymore. Please learn the Metric system.

First, it's spelled arcane (hidden, mysterious). Which isn't the word you
want -- you want archaic.

Metric is not capitalized.

In article ,
"Tom Miller" wrote:

One thing the OP failed to state is the voltage of his 20 amp power supply.
2000 volts at 20 amps is a much larger transformer then one might find in a
12 volt, 20 amp supply.

I am using these power supplies for Ham Radio equipment. Voltage is
supposed to be 13.8, but I think most people just say 12.

A temperature of 125º F/52º C is hotter than you want to hold your hand
on, but you probably will not scream from the pain. Temperature is a
significant factor in reliability calculations. I was concerned about
the long term degradation of components.

I think I just answered my own question. The hottest power supply is 30
years old and the other is 20. Both appear to meet their electrical
specifications.

Fred

On 22/07/2014 11:29 AM, William Sommerwerck wrote:
**Most power transformers will operate at 100 degrees C quite safely,
though I prefer to see less than 75 C. I have no idea what 125
degrees F is and I have no interest either, but I suspect it is less
than 75 C.

It's such a big deal to convert, isn't it?

**There is no need to convert. 95% of the planet's population uses
Metric measurements. The 5% left is irrelevant.


Start by subtracting 32. That's 93, which you can round off to 90. Then
take 5/9 of that -- 50, which is close enough. You can do it in your
head in a few seconds.

**I never need to perform such useless calculations. Almost every person
on this planet uses Metric measurements.


There's no need to memorize the formula, if you remember that 0 and 32
degrees are the same point, and 1 degree F is 9/5 degree C.

**There is no need to convert, nor memorise anything, anyway. Almost
every human on the planet uses Metric measurements in their daily lives.
ALL scientific measurements are done within the Metric system. The
Imperial system is just idiotic. Most of us humans naturally gravitate
towards a base 10 form of measurement. The Metric system is just plain
logical and extremely easy to live with.



[ASIDE] This is an international group. Almost none of the planet's
population (less than 5%) bothers with archane measurements,
like degrees F, anymore. Please learn the Metric system.

First, it's spelled arcane (hidden, mysterious). Which isn't the word
you want -- you want archaic.

**Thanks for the spelling correction.


Metric is not capitalized.

**When I was taught the Metric system, it was capitalised. So,
capitalised it will remain (for me).

--
Trevor Wilson www.rageaudio.com.au

On 22/07/2014 8:48 AM, Tom Miller wrote:

"Trevor Wilson" wrote in message
...
On 22/07/2014 4:18 AM, Fred McKenzie wrote:
I have a couple of 20 Amp linear DC power supplies with hot
transformers.

With no load, one gets up to 115 Degrees F after several hours. The
other gets up to 125 Degrees F. Measurements were made with an IR
thermometer looking at the top of the transformer. I disconnected the
secondary windings of one, but results were the same.

With their covers installed, neither power supply feels excessively hot.
The one that got to 125, gets to 95 Degrees F on top of its cover with
about two Amps load.

One cause might be not enough iron in the core. I suppose there could
be some circulating currents in the core as well. Regardless, does
anyone know if they are hot enough to be a problem? Or should I just
not worry about it?

I checked several other power supplies, and none had transformers above
95 Degrees F.

Fred


**Most power transformers will operate at 100 degrees C quite safely,
though I prefer to see less than 75 C. I have no idea what 125 degrees
F is and I have no interest either, but I suspect it is less than 75 C.

[ASIDE] This is an international group. Almost none of the planet's
population (less than 5%) bothers with archane measurements, like
degrees F, anymore. Please learn the Metric system.

--
Trevor Wilson www.rapeaudio.com.au


Why, because you are too ****ing stupid or lazy to do a simple conversion?

**There is no need to do the conversion. Hardly anyone bothers with
Imperial measurements anymore.


So why did you even take the time to make your stupid comments?

**I answered the question, correctly and succinctly. I also attempted to
educate the original poster in how to deal with an international
audience, by pointing out that a measurement system which is used in one
small corner of the planet may not be understood by the vast majority.

--
Trevor Wilson www.rageaudio.com.au

It happens that Fred McKenzie formulated :
In article ,
"Tom Miller" wrote:

One thing the OP failed to state is the voltage of his 20 amp power supply.
2000 volts at 20 amps is a much larger transformer then one might find in a
12 volt, 20 amp supply.

I am using these power supplies for Ham Radio equipment. Voltage is
supposed to be 13.8, but I think most people just say 12.

A temperature of 125º F/52º C is hotter than you want to hold your hand
on, but you probably will not scream from the pain. Temperature is a
significant factor in reliability calculations. I was concerned about
the long term degradation of components.

I think I just answered my own question. The hottest power supply is 30
years old and the other is 20. Both appear to meet their electrical
specifications.

Fred

Do they really meet their Specs?
Back then (30 years ago) the nominal in USA was more likely 110 volts
whereas today to follow Harmonisation rules it should be 120 which is
a like 9% increase. Of course there is a wide margin but you may be on
the high side. Just a thought.

"John G" wrote in message
. au...
It happens that Fred McKenzie formulated :
In article ,
"Tom Miller" wrote:

One thing the OP failed to state is the voltage of his 20 amp power
supply. 2000 volts at 20 amps is a much larger transformer then one
might find in a 12 volt, 20 amp supply.

I am using these power supplies for Ham Radio equipment. Voltage is
supposed to be 13.8, but I think most people just say 12.

A temperature of 125º F/52º C is hotter than you want to hold your hand
on, but you probably will not scream from the pain. Temperature is a
significant factor in reliability calculations. I was concerned about
the long term degradation of components.

I think I just answered my own question. The hottest power supply is 30
years old and the other is 20. Both appear to meet their electrical
specifications.

Fred

Do they really meet their Specs?
Back then (30 years ago) the nominal in USA was more likely 110 volts
whereas today to follow Harmonisation rules it should be 120 which is a
like 9% increase. Of course there is a wide margin but you may be on the
high side. Just a thought.

Sounds like an Astron AS20 or similar. The transformers are made with cost
in mind and they do run hot even at no load.

As long as it doesn't smoke, I would not be too worried.

"John G" wrote in message
. au...

It happens that Gareth Magennis formulated :

"John G" wrote in message
. au...

Gareth Magennis laid this down on his screen :

"Tom Miller" wrote in message ...


"Trevor Wilson" wrote in message
...
On 22/07/2014 4:18 AM, Fred McKenzie wrote:
I have a couple of 20 Amp linear DC power supplies with hot
transformers.

With no load, one gets up to 115 Degrees F after several hours. The
other gets up to 125 Degrees F. Measurements were made with an IR
thermometer looking at the top of the transformer. I disconnected the
secondary windings of one, but results were the same.

With their covers installed, neither power supply feels excessively
hot.
The one that got to 125, gets to 95 Degrees F on top of its cover with
about two Amps load.

One cause might be not enough iron in the core. I suppose there could
be some circulating currents in the core as well. Regardless, does
anyone know if they are hot enough to be a problem? Or should I just
not worry about it?

I checked several other power supplies, and none had transformers above
95 Degrees F.

Fred


**Most power transformers will operate at 100 degrees C quite safely,
though I prefer to see less than 75 C. I have no idea what 125 degrees F
is and I have no interest either, but I suspect it is less than 75 C.

[ASIDE] This is an international group. Almost none of the planet's
population (less than 5%) bothers with archane measurements, like
degrees F, anymore. Please learn the Metric system.

-- Trevor Wilson www.rapeaudio.com.au


Why, because you are too ****ing stupid or lazy to do a simple
conversion?




OK, convert the very accurate and reproducable measurement of 62.25cm, to
the Imperial system, and you get 24inches and 39/64ths.

That's a bit of a joke, surely, that should not be present in the 21st
century.


Gareth.

No it converts to 24.507874 inches if you us the same maths notation.




The point is that the Imperial system commonly uses discrete steps that
are only accurate to those steps.

The metric system does not suffer this limitation.


Gareth.

Neither does the imperial system if you use a rule marked in tenths and
Micrometers are marked in 1/1000s or some such and not fractions which
were near enough for woodworkers in the past.

PS I am no fan of Imperial either in measurement or in Government but
we have to live with rest of the world and be tolerant of whatever
comes by. :-Z





Some time ago I was employed to install the audio wiring in a new build
recording studio.
In one room, I was astounded to find the carpenter had pencilled in the
width of one wall using a measurement of feet, inches, and so many 8ths of
an inch.

So he was only working to an accuracy of 16th of an inch, which is 1.58mm.
To me, this is completely unacceptable in a professional environment, and
the basis of my posts in this thread.


Gareth.

On Mon, 21 Jul 2014 19:30:16 -0700, Fred McKenzie wrote:

...snip....
A temperature of 125º F/52º C is hotter than you want to hold your hand
on, but you probably will not scream from the pain. Temperature is a
significant factor in reliability calculations. I was concerned about
the long term degradation of components.

I think I just answered my own question. The hottest power supply is 30
years old and the other is 20. Both appear to meet their electrical
specifications.

Fred


Standard 'rule of thumb' the MTBF is halved for every 10C increase in
temperature.
(10C == 18F)

In article ,
"Tom Miller" wrote:

I think I just answered my own question. The hottest power supply is 30
years old and the other is 20. Both appear to meet their electrical
specifications.

Fred

Do they really meet their Specs?
Back then (30 years ago) the nominal in USA was more likely 110 volts
whereas today to follow Harmonisation rules it should be 120 which is a
like 9% increase. Of course there is a wide margin but you may be on the
high side. Just a thought.

Sounds like an Astron AS20 or similar. The transformers are made with cost
in mind and they do run hot even at no load.

The hotter one is a Kenwood KPS-21. However the insides are almost
identical to an Astron RS-20A, except the Kenwood does not have a
crowbar circuit installed. Date Codes on components are from 1980, and
I purchased it about 1981. Its label says input voltage should be 120
VAC

The other is an Astron RS-20A with date codes from the mid-1990s. Its
label says input voltage should be 115 VAC. It was recently purchased
from an estate with a goal of replacing the hot KPS-21!

Line voltage here runs about 119 VAC, although equipment should be
designed to operate over a +/- ten percent range (108 to 132 VAC) in the
U.S.

Fred

On Monday, July 21, 2014 5:04:09 PM UTC-4, Trevor Wilson wrote:
[ASIDE] This is an international group. Almost none of the planet's

population (less than 5%) bothers with archane measurements, like

degrees F, anymore. Please learn the Metric system.

While I agree in general with the sentiment, there is no actual advantage of C over F in doing calculations.

C and F are both European temperature systems based on 100 degrees. For C there are 100 degrees between the temperature at which water freezes and boils; for F there are 100 degrees between the usual hottest and coldest temperatures in Europe at the time.

On 23/07/2014 2:37 AM, Tim R wrote:
On Monday, July 21, 2014 5:04:09 PM UTC-4, Trevor Wilson wrote:
[ASIDE] This is an international group. Almost none of the
planet's

population (less than 5%) bothers with archane measurements, like

degrees F, anymore. Please learn the Metric system.

While I agree in general with the sentiment, there is no actual
advantage of C over F in doing calculations.

C and F are both European temperature systems based on 100 degrees.
For C there are 100 degrees between the temperature at which water
freezes and boils; for F there are 100 degrees between the usual
hottest and coldest temperatures in Europe at the time.


**I agree that there is no specific advantage in Celsius, except, of
course, that it dove-tails neatly with Kelvin measurements. SI units, on
the whole, however, are universally accepted and logical for humans to
work with. No one of any consequence bothers with Imperial measurements
any longer.

--
Trevor Wilson www.rageaudio.com.au

Gareth Magennis wrote:

Some time ago I was employed to install the audio wiring in a new build
recording studio.
In one room, I was astounded to find the carpenter had pencilled in the
width of one wall using a measurement of feet, inches, and so many 8ths of
an inch.

So he was only working to an accuracy of 16th of an inch, which is 1.58mm.
To me, this is completely unacceptable in a professional environment, and
the basis of my posts in this thread.


Idiot. The saw kerf is 1/8" or wider, depending on the type of saw
blade that are used for framing work. Wood expands and contracts with
changes in humidity. This isn't precision machining, where you work to
mill, or a percentage of a mil.


--
Anyone wanting to run for any political office in the US should have to
have a DD214, and a honorable discharge.

On Tue, 22 Jul 2014 08:58:44 +0100, "Gareth Magennis"
wrote:


No it converts to 24.507874 inches if you us the same maths notation.




The point is that the Imperial system commonly uses discrete steps that
are only accurate to those steps.

The metric system does not suffer this limitation.


Gareth.

Neither does the imperial system if you use a rule marked in tenths and
Micrometers are marked in 1/1000s or some such and not fractions which
were near enough for woodworkers in the past.

PS I am no fan of Imperial either in measurement or in Government but
we have to live with rest of the world and be tolerant of whatever
comes by. :-Z





Some time ago I was employed to install the audio wiring in a new build
recording studio.
In one room, I was astounded to find the carpenter had pencilled in the
width of one wall using a measurement of feet, inches, and so many 8ths of
an inch.

So he was only working to an accuracy of 16th of an inch, which is 1.58mm.
To me, this is completely unacceptable in a professional environment, and
the basis of my posts in this thread.


Please be more thoughtful about how quickly you judge. 1.6 mm is just
about best surface smoothness over a 3 to 5 meter range of a wall, not all
that shabby. If you think you can do better than skilled trades workers
just give a try some time.

?-)

On Tue, 22 Jul 2014 12:57:27 +1000, Trevor Wilson
wrote:

On 22/07/2014 11:29 AM, William Sommerwerck wrote:
**Most power transformers will operate at 100 degrees C quite safely,
though I prefer to see less than 75 C. I have no idea what 125
degrees F is and I have no interest either, but I suspect it is less
than 75 C.

It's such a big deal to convert, isn't it?

**There is no need to convert. 95% of the planet's population uses
Metric measurements. The 5% left is irrelevant.

Oh really, alligator breath? How many times have metric nations landed
people on the moon and brought them back home again safely? (zero) I
thought so.
Who puts up the most communications satellites?
The list goes on for quite a while. Also to the point, murica's hayday is
passed and we will be paying the piper ever more for decades to come. Just
like Europe did for a long time. The PIIGS may yet bring the EU down.
Still feeling arrogant?

?-)

Efter mange tanker skrev josephkk:
On Tue, 22 Jul 2014 08:58:44 +0100, "Gareth Magennis"
wrote:


No it converts to 24.507874 inches if you us the same maths notation.




The point is that the Imperial system commonly uses discrete steps that
are only accurate to those steps.

The metric system does not suffer this limitation.


Gareth.

Neither does the imperial system if you use a rule marked in tenths and
Micrometers are marked in 1/1000s or some such and not fractions which
were near enough for woodworkers in the past.

PS I am no fan of Imperial either in measurement or in Government but
we have to live with rest of the world and be tolerant of whatever
comes by. :-Z





Some time ago I was employed to install the audio wiring in a new build
recording studio.
In one room, I was astounded to find the carpenter had pencilled in the
width of one wall using a measurement of feet, inches, and so many 8ths of
an inch.

So he was only working to an accuracy of 16th of an inch, which is 1.58mm.
To me, this is completely unacceptable in a professional environment, and
the basis of my posts in this thread.


Please be more thoughtful about how quickly you judge. 1.6 mm is just
about best surface smoothness over a 3 to 5 meter range of a wall, not all
that shabby. If you think you can do better than skilled trades workers
just give a try some time.


My maternal grandfather was a machinist working lathes and making
cogwheels.
My paternal grandfather was a bricklayer.
They had very different views on accuracy.
Maternal grandfather could see "This shelf is 3mm lower on one side
than the other" from across the room
For paternal grandfather "accurate" was within the width of a joint
between bricks. :-)

--
Husk kørelys bagpå, hvis din bilfabrikant har taget den idiotiske
beslutning at undlade det.

"josephkk" wrote in message
...
On Tue, 22 Jul 2014 08:58:44 +0100, "Gareth Magennis"
wrote:


No it converts to 24.507874 inches if you us the same maths notation.




The point is that the Imperial system commonly uses discrete steps that
are only accurate to those steps.

The metric system does not suffer this limitation.


Gareth.

Neither does the imperial system if you use a rule marked in tenths and
Micrometers are marked in 1/1000s or some such and not fractions which
were near enough for woodworkers in the past.

PS I am no fan of Imperial either in measurement or in Government but
we have to live with rest of the world and be tolerant of whatever
comes by. :-Z





Some time ago I was employed to install the audio wiring in a new build
recording studio.
In one room, I was astounded to find the carpenter had pencilled in the
width of one wall using a measurement of feet, inches, and so many 8ths of
an inch.

So he was only working to an accuracy of 16th of an inch, which is 1.58mm.
To me, this is completely unacceptable in a professional environment, and
the basis of my posts in this thread.


Please be more thoughtful about how quickly you judge. 1.6 mm is just
about best surface smoothness over a 3 to 5 meter range of a wall, not all
that shabby. If you think you can do better than skilled trades workers
just give a try some time.

?-)




In the real world example I gave, i.e. a recording studio, precise
dimensions are sometimes very important.

If the carpenter made a space 1.6mm too small, it could mean that none of
the rack mount equipment would fit in it properly, for instance.



Gareth.

On Monday, July 21, 2014 8:33:57 PM UTC-7, Tom Miller wrote:

Sounds like an Astron AS20 or similar. The transformers are made with cost
in mind and they do run hot even at no load.

Oh, that should be 'run hot especially at no load'. The losses in transformers
might be maximum when NO SECONDARY CURRENT IS DRAWN, because
of core saturation effects. So, it makes sense to power-down at the
input of such a power supply, not at the output.

On Thursday, July 24, 2014 7:48:38 AM UTC-7, Gareth Magennis wrote:
"josephkk" wrote in message

...

Please be more thoughtful about how quickly you judge. 1.6 mm is just
about best surface smoothness over a 3 to 5 meter range of a wall, not all
that shabby. If you think you can do better than skilled trades workers
just give a try some time.

In the real world example I gave, i.e. a recording studio, precise
dimensions are sometimes very important.

If the carpenter made a space 1.6mm too small, it could mean that none of
the rack mount equipment would fit in it properly, for instance.

Completely wrong. A rack is furniture, its outer dimensions aren't standardized
(though the inner spaces are). So, it isn't a carpenter's job to make a socket
into which the rack fits.

If you need 1.6mm more space, too, you can push the wall that far (wood
frame, of course, not necessarily brick). If there's baseboard molding,
though, you might want to do some more carpentry...

"whit3rd" wrote in message
...

On Thursday, July 24, 2014 7:48:38 AM UTC-7, Gareth Magennis wrote:
"josephkk" wrote in message

...

Please be more thoughtful about how quickly you judge. 1.6 mm is just
about best surface smoothness over a 3 to 5 meter range of a wall, not all
that shabby. If you think you can do better than skilled trades workers
just give a try some time.

In the real world example I gave, i.e. a recording studio, precise
dimensions are sometimes very important.

If the carpenter made a space 1.6mm too small, it could mean that none of
the rack mount equipment would fit in it properly, for instance.

Completely wrong. A rack is furniture, its outer dimensions aren't
standardized
(though the inner spaces are). So, it isn't a carpenter's job to make a
socket
into which the rack fits.

If you need 1.6mm more space, too, you can push the wall that far (wood
frame, of course, not necessarily brick). If there's baseboard molding,
though, you might want to do some more carpentry...





It would surely make more sense to measure things accurately in the first
place, using millimetres instead of fractions of an inch, rather than try
and sort out the problems later.



Gareth.

"Fred McKenzie"

I have a couple of 20 Amp linear DC power supplies with hot transformers.

With no load, one gets up to 115 Degrees F after several hours. The
other gets up to 125 Degrees F. Measurements were made with an IR
thermometer looking at the top of the transformer.


** FYI there is a much simpler, low tech way to find the internal temp of a
transformer.

1. Measure the primary winding's resistance when at room temp.

2. Make the same measurement ( quick as you can) when the tranny's running
temp has stabilised.

3. Calculate the increase as a decimal factor and multiply that by 254 to
get the temp rise in degrees C.

Eg.

Room temp = 4 ohms

Hot temp = 5 ohms

Increase factor = 0.25

0.25 x 254 = 63.5 degrees C

Add on the actual room temp to get final result.

If the number is over 100C there is cause for concern.



..... Phil

josephkk wrote:

Oh really, alligator breath? How many times have metric nations landed
people on the moon and brought them back home again safely? (zero) I
thought so.
Who puts up the most communications satellites?
The list goes on for quite a while. Also to the point, murica's hayday is
passed and we will be paying the piper ever more for decades to come. Just
like Europe did for a long time. The PIIGS may yet bring the EU down.
Still feeling arrogant?


Ask Trevor about Australia's space program...


--
Anyone wanting to run for any political office in the US should have to
have a DD214, and a honorable discharge.

Phil Allison wrote:

"Fred McKenzie"

I have a couple of 20 Amp linear DC power supplies with hot transformers.

With no load, one gets up to 115 Degrees F after several hours. The
other gets up to 125 Degrees F. Measurements were made with an IR
thermometer looking at the top of the transformer.


** FYI there is a much simpler, low tech way to find the internal temp of a
transformer.

1. Measure the primary winding's resistance when at room temp.

2. Make the same measurement ( quick as you can) when the tranny's running
temp has stabilised.

3. Calculate the increase as a decimal factor and multiply that by 254 to
get the temp rise in degrees C.

Eg.

Room temp = 4 ohms

Hot temp = 5 ohms

Increase factor = 0.25

0.25 x 254 = 63.5 degrees C

Add on the actual room temp to get final result.

If the number is over 100C there is cause for concern.

spiffy trick. thanks.

In article ,
"Phil Allison" wrote:

"Fred McKenzie"

I have a couple of 20 Amp linear DC power supplies with hot transformers.

With no load, one gets up to 115 Degrees F after several hours. The
other gets up to 125 Degrees F. Measurements were made with an IR
thermometer looking at the top of the transformer.


** FYI there is a much simpler, low tech way to find the internal temp of a
transformer.

1. Measure the primary winding's resistance when at room temp.

2. Make the same measurement ( quick as you can) when the tranny's running
temp has stabilised.

3. Calculate the increase as a decimal factor and multiply that by 254 to
get the temp rise in degrees C.

Eg.

Room temp = 4 ohms

Hot temp = 5 ohms

Increase factor = 0.25

0.25 x 254 = 63.5 degrees C

Add on the actual room temp to get final result.

If the number is over 100C there is cause for concern.

Phil-

This is useful information, but my results did not agree with IR
measurements.

I think my problem was that it is hard to measure low values of
resistance accurately. For my "hot" transformer, cold resistance
measurement of the primary was around one Ohm on a Fluke digital meter.
However shorting the meter leads produced 0.4 Ohms.

After several hours, primary resistance measurement was 1.2 Ohms.
Subtracting 0.4 from both measurements, the increase factor was
(0.8-0.6)/0.6 = 1/3. Calculated rise was 84.7º C, plus original ambient
24.4º C gives 109.1º C.

The IR thermometer measured the top of the transformer laminations.
Initial temperature was 24.4º C. Final temperature was 53.5º C. I
could hold my hand on the transformer without screaming, so I am fairly
sure the temperature was nowhere near 109.1º C!

I think a 4-terminal resistance measurement would provide more realistic
readings.

Fred

"Fred McKenzie"
"Phil Allison"
"Fred McKenzie"

I have a couple of 20 Amp linear DC power supplies with hot
transformers.

With no load, one gets up to 115 Degrees F after several hours. The
other gets up to 125 Degrees F. Measurements were made with an IR
thermometer looking at the top of the transformer.


** FYI there is a much simpler, low tech way to find the internal temp of
a
transformer.

1. Measure the primary winding's resistance when at room temp.

2. Make the same measurement ( quick as you can) when the tranny's
running
temp has stabilised.

3. Calculate the increase as a decimal factor and multiply that by 254 to
get the temp rise in degrees C.

Eg.

Room temp = 4 ohms

Hot temp = 5 ohms

Increase factor = 0.25

0.25 x 254 = 63.5 degrees C

Add on the actual room temp to get final result.

If the number is over 100C there is cause for concern.


This is useful information, but my results did not agree with IR
measurements.

** It never will as the internal temp of a tranny is higher than the surface
temp - the test gives the average temp of the copper wire - which is
crucial for insulation purposes.

The same test is used in international standards for transformers etc to
establish safe temp rise.


I think my problem was that it is hard to measure low values of
resistance accurately.

** Not if you pass a known current through the winding and measure the
voltage drop.

Eg: Connect a 10ohm, 10W resistor in series with the winding and adjust a
bench PSU each time to give 10V across the resistor - so you have 1amp. The
voltage across the winding is then the same as its resistance in ohms.

Since you compute the ratio of two readings, absolute accuracy of the
resistor and the voltmeter do not matter.


..... Phil

On Sat, 02 Aug 2014 23:58:37 -0400, Fred McKenzie wrote:

In article ,
"Phil Allison" wrote:

"Fred McKenzie"

I have a couple of 20 Amp linear DC power supplies with hot transformers.

With no load, one gets up to 115 Degrees F after several hours. The
other gets up to 125 Degrees F. Measurements were made with an IR
thermometer looking at the top of the transformer.


** FYI there is a much simpler, low tech way to find the internal temp of a
transformer.

1. Measure the primary winding's resistance when at room temp.

2. Make the same measurement ( quick as you can) when the tranny's running
temp has stabilised.

3. Calculate the increase as a decimal factor and multiply that by 254 to
get the temp rise in degrees C.

Eg.

Room temp = 4 ohms

Hot temp = 5 ohms

Increase factor = 0.25

0.25 x 254 = 63.5 degrees C

Add on the actual room temp to get final result.

If the number is over 100C there is cause for concern.

Phil-

This is useful information, but my results did not agree with IR
measurements.

I think my problem was that it is hard to measure low values of
resistance accurately. For my "hot" transformer, cold resistance
measurement of the primary was around one Ohm on a Fluke digital meter.
However shorting the meter leads produced 0.4 Ohms.

After several hours, primary resistance measurement was 1.2 Ohms.
Subtracting 0.4 from both measurements, the increase factor was
(0.8-0.6)/0.6 = 1/3. Calculated rise was 84.7º C, plus original ambient
24.4º C gives 109.1º C.

The IR thermometer measured the top of the transformer laminations.
Initial temperature was 24.4º C. Final temperature was 53.5º C. I
could hold my hand on the transformer without screaming, so I am fairly
sure the temperature was nowhere near 109.1º C!

I think a 4-terminal resistance measurement would provide more realistic
readings.

Fred

Yes, you got the 4-terminal one absolutely right. A meter that can use
kelvin clips and the resulting measurements would be much better. This is
normal for resistances under 10 ohms and mandatory under 1 ohm (for 3
reliable digits). For lower resistance or more resolution it gets
progressively worse.

?-)

josephkk wrote:
On Sat, 02 Aug 2014 23:58:37 -0400, Fred McKenzie wrote:

In article ,
"Phil Allison" wrote:

"Fred McKenzie"

I have a couple of 20 Amp linear DC power supplies with hot transformers.

With no load, one gets up to 115 Degrees F after several hours. The
other gets up to 125 Degrees F. Measurements were made with an IR
thermometer looking at the top of the transformer.


** FYI there is a much simpler, low tech way to find the internal temp of a
transformer.

1. Measure the primary winding's resistance when at room temp.

2. Make the same measurement ( quick as you can) when the tranny's running
temp has stabilised.

3. Calculate the increase as a decimal factor and multiply that by 254 to
get the temp rise in degrees C.

Eg.

Room temp = 4 ohms

Hot temp = 5 ohms

Increase factor = 0.25

0.25 x 254 = 63.5 degrees C

Add on the actual room temp to get final result.

If the number is over 100C there is cause for concern.

Phil-

This is useful information, but my results did not agree with IR
measurements.

I think my problem was that it is hard to measure low values of
resistance accurately. For my "hot" transformer, cold resistance
measurement of the primary was around one Ohm on a Fluke digital meter.
However shorting the meter leads produced 0.4 Ohms.

After several hours, primary resistance measurement was 1.2 Ohms.
Subtracting 0.4 from both measurements, the increase factor was
(0.8-0.6)/0.6 = 1/3. Calculated rise was 84.7? C, plus original ambient
24.4? C gives 109.1? C.

The IR thermometer measured the top of the transformer laminations.
Initial temperature was 24.4? C. Final temperature was 53.5? C. I
could hold my hand on the transformer without screaming, so I am fairly
sure the temperature was nowhere near 109.1? C!

I think a 4-terminal resistance measurement would provide more realistic
readings.

Fred

Yes, you got the 4-terminal one absolutely right. A meter that can use
kelvin clips and the resulting measurements would be much better. This is
normal for resistances under 10 ohms and mandatory under 1 ohm (for 3
reliable digits). For lower resistance or more resolution it gets
progressively worse.

My mind was blown when I just looked up the street prices of commercial
kelvin clip test leads with banana jacks.

Even the B&K stuff was like $160. Pomona? well over $200. Keithley kelvin
probes? $300+

I'm surprised the audiophile folks haven't come up with some sort of play
on this stuff yet.