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Default Hum from the transformer in power supply

I am assembling an amp and have a nice transformer of proper VA rating.
This transformer is an EI type transformer, with laminations.

But, this transformer has no bells on both sides to cover the windings.
Without the bells will I have hum problems when the transformer is
installed within 4 inches of the low level circuit cards that drive the
output MOSFETs?

I can orient it so the laminations "point" to the amp's active circuitry
but the sides where bells usually go will then be "pointing" at the
filter capacitors. Will this orientation be OK in the amp and not make
it hum?

Can someone give me some good advice on this and/or point me to a good
web site that discusses transformer hum or eddy current?

Thanks a lot.

  #2   Report Post  
Jerry G.
 
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Default Hum from the transformer in power supply

The filter caps will not be sensitive to the orientation of the transformer.
If you cannot get it right, why not mount it externally in its own separate
case? I have seen a number of high end amplifiers with the power supply
outboard. You can make a nice wire harness with connectors on it to have it
detachable for transport, or relocation of the amp.

--

Greetings,

Jerry Greenberg GLG Technologies GLG
=========================================
WebPage http://www.zoom-one.com
Electronics http://www.zoom-one.com/electron.htm
Instruments http://www.zoom-one.com/glgtech.htm
=========================================


wrote in message
...
I am assembling an amp and have a nice transformer of proper VA rating.
This transformer is an EI type transformer, with laminations.

But, this transformer has no bells on both sides to cover the windings.
Without the bells will I have hum problems when the transformer is
installed within 4 inches of the low level circuit cards that drive the
output MOSFETs?

I can orient it so the laminations "point" to the amp's active circuitry
but the sides where bells usually go will then be "pointing" at the
filter capacitors. Will this orientation be OK in the amp and not make
it hum?

Can someone give me some good advice on this and/or point me to a good
web site that discusses transformer hum or eddy current?

Thanks a lot.


  #3   Report Post  
Geoff Wood
 
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Default Hum from the transformer in power supply


"Jerry G." wrote in message
...
The filter caps will not be sensitive to the orientation of the

transformer.
If you cannot get it right, why not mount it externally in its own

separate
case? I have seen a number of high end amplifiers with the power supply
outboard. You can make a nice wire harness with connectors on it to have

it
detachable for transport, or relocation of the amp.



On the other hand you can see plenty of high end gear with power
transformers right next to low-level circuitry, and no problems. Suck it
and see - plonk it in there and move it around....


geoff


  #4   Report Post  
 
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Default Hum from the transformer in power supply


Geoff Wood wrote:

"Jerry G." wrote in message
...
The filter caps will not be sensitive to the orientation of the

transformer.
If you cannot get it right, why not mount it externally in its own

separate
case? I have seen a number of high end amplifiers with the power supply
outboard. You can make a nice wire harness with connectors on it to have

it
detachable for transport, or relocation of the amp.


On the other hand you can see plenty of high end gear with power
transformers right next to low-level circuitry, and no problems. Suck it
and see - plonk it in there and move it around....

geoff


The point here is that the EI transformer I have has NO BELLS on the two sides
where the windings are exposed. Most transformers have bells and, yes, are
tucked right in close to the low level circuit cards in an amp, although these
transformers are usually oriented so the laminations "point" to the circuit
cards and the bells are at a right angle to them.

My concern is the amount of eddy current that escapes from the trans. that has
no bells. I was hoping somebody could point me to a good article or whatever
about this. Bells are put on transformers to hold in the eddy currents and to
shield surrounding circuitry from the influence of eddy currents.

Well, in the absence of some good info I will just have to wing it and try the
empirical approach, or maybe cover the transformer with a tin can.

  #5   Report Post  
Geoff Wood
 
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Default Hum from the transformer in power supply


wrote in message

The point here is that the EI transformer I have has NO BELLS on the two

sides
where the windings are exposed. Most transformers have bells


No they don't. Some do, some don't. Some have an effect, others don't.
More to do with the surropund components, impedences, and topography.

and, yes, are
tucked right in close to the low level circuit cards in an amp, although

these
transformers are usually oriented so the laminations "point" to the

circuit
cards and the bells are at a right angle to them.

My concern is the amount of eddy current that escapes from the trans. that

has
no bells. I was hoping somebody could point me to a good article or

whatever
about this. Bells are put on transformers to hold in the eddy currents and

to
shield surrounding circuitry from the influence of eddy currents.

Well, in the absence of some good info I will just have to wing it and try

the
empirical approach, or maybe cover the transformer with a tin can.


I'm sure you are anticipating a problem that probably won't exist. Only way
to know for sure is to try it.

geoff




  #6   Report Post  
Richard Crowley
 
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Default Hum from the transformer in power supply

"Geoff Wood" wrote ...
Bells are put on transformers to hold in the eddy currents
and to shield surrounding circuitry from the influence of eddy
currents.


Do you have any support for that statement?
I've never heard anyone propose such a thing before.


  #8   Report Post  
 
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Default Hum from the transformer in power supply

Thanks to all of you for your responses. I have learned a few things.

Solution? Put the parts on a breadboard and try it. . . .


  #9   Report Post  
Gib Bogle
 
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Default Hum from the transformer in power supply

Richard Crowley wrote:

Bells are put on transformers to hold in the eddy currents
and to shield surrounding circuitry from the influence of eddy
currents.


Why do you say that?

Gib

  #10   Report Post  
Richard Crowley
 
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Default Hum from the transformer in power supply

Richard Crowley wrote:

Bells are put on transformers to hold in the eddy currents
and to shield surrounding circuitry from the influence of eddy
currents.


"Gib Bogle" wrote ...
Why do you say that?


I DIDN'T say that. (Note the triple )
"Geoff Wood" said it.

I DISPUTED that and the "Geoff Wood" hasn't responded.




  #11   Report Post  
Geoff Wood
 
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Default Hum from the transformer in power supply


"Richard Crowley" wrote in message
...
Richard Crowley wrote:

Bells are put on transformers to hold in the eddy currents
and to shield surrounding circuitry from the influence of eddy
currents.


"Gib Bogle" wrote ...
Why do you say that?


I DIDN'T say that. (Note the triple )
"Geoff Wood" said it.

I DISPUTED that and the "Geoff Wood" hasn't responded.



I most certain did not spout the 'eddy currents' crap.

geoff


  #12   Report Post  
Richard Crowley
 
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Default Hum from the transformer in power supply

"Geoff Wood" wrote
I most certain did not spout the 'eddy currents' crap.


Apoligies, Mr. Wood did NOT say that.
It was the OP, "wantnohum2" who apparently now knows better.


  #13   Report Post  
Gib Bogle
 
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Default Hum from the transformer in power supply

Richard Crowley wrote:

"Geoff Wood" wrote

I most certain did not spout the 'eddy currents' crap.



Apoligies, Mr. Wood did NOT say that.
It was the OP, "wantnohum2" who apparently now knows better.


NOW you get it.

Gib

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