Effective toroidal transformer shielding

[Pascal Nguyen]

I afraid that, I cannot find the same load as the power since my aleph5 draw 6A continuously. Is it possible to measure while I use power itself as a load?

Can’t find one?
Make one then, your V supply = 20V ?, your current = 6A, then load = 3R3
Don’t forget wattage, 6A x 20V = 120W
Looking for any resistor got that same value.
Closest is 2 x 8R 100W in parallel.
Load your PSU with 4R/200W, then check for any mechanical noise or vibration from your toroid before any adventure in the EMI shooting.
Keep that dummy as a bonus for PA stage testing.

Cheers

 

[MAAC0]

How about posting some recorded buzz ? Perhaps we can get a better picture.

 

[tanwa]

How about posting some recorded buzz ? Perhaps we can get a better picture.

YouTube

This is what it sound like. it is event londer than the buzzing from speaker due to EMI problem.

 

[Pascal Nguyen]

Load your PSU with 4R/200W, then check for any mechanical noise or vibration
Cheers

Thanks for your video clip.
I wouldn’t dare to use an amp like yours (well built with top quality components) as a dummy for PSU test.
I prefer to spent a dollar or two for 2 100W resistors, things can go wrong, a fuse and a 2dollars will go in place of your matching pairs power transistors.
In case you have plenty of paired mosfets, you can leave as it is and use your CRO to see the wave form, if you are able to decipher it, again I prefer to use soundcard FFT’s to examine the problem, much easier for non EE background’s human.
Seems to me you have a faulty toroid.

Cheers

 

[basreflex]

I dismantled a big sedlbauer toroid. it had 3 layers of the same core material wound on the outside of the toroid. toroid cores are tape wound from a very long strip of core material.
another reason of humming is that the toroid is dimensioned close to saturation of the core. reducing the mains voltage using a variac transformer could reveal that.

 

[tanwa]

Thanks for your video clip.
I wouldn’t dare to use an amp like yours (well built with top quality components) as a dummy for PSU test.
I prefer to spent a dollar or two for 2 100W resistors, things can go wrong, a fuse and a 2dollars will go in place of your matching pairs power transistors.
In case you have plenty of paired mosfets, you can leave as it is and use your CRO to see the wave form, if you are able to decipher it, again I prefer to use soundcard FFT’s to examine the problem, much easier for non EE background’s human.
Seems to me you have a faulty toroid.

Cheers

Actually, at the first time test. The problem was not show up like this. I measure and test the PSU several time before connect to the amp.

After some hours running, the problem get worse as you see in the clip. I also point to the transformer itself, that why I manage to send it back to manufacturer for checking. But I afraid that it may not show up during the test.

Buzzing sound was there, event I remove all load just the PSU itself. So I hope that it will show up at the manufacturer.

 

[tanwa]

I dismantled a big sedlbauer toroid. it had 3 layers of the same core material wound on the outside of the toroid. toroid cores are tape wound from a very long strip of core material.
another reason of humming is that the toroid is dimensioned close to saturation of the core. reducing the mains voltage using a variac transformer could reveal that.

I doubt that too, but how can I convince the transformer to agree with is the problem.

 

[tanwa]

I dismantled a big sedlbauer toroid. it had 3 layers of the same core material wound on the outside of the toroid. toroid cores are tape wound from a very long strip of core material.
another reason of humming is that the toroid is dimensioned close to saturation of the core. reducing the mains voltage using a variac transformer could reveal that.

I noticed that during the day VAC at my house is ~228V. And become ~213 V during the night. But the buzzing sound is same. So, I am also not sure, reducing voltage will help.

 

[starbender]

one notification is my transformer generate buzzing sound that I can here from 2 m. it is not normal for sure. but it happen some time. What is it possible from? and does it relate to the EMI from transformer? The transformer is new, do you think it is fail?

Any suggestion would be appreciate

I had buzzing/growling toroid in my F5. Tried lots of stuff and method to solve the problem. Rotated transformer several times, tried dc trap at the input, tried shielding etc.

It is not constant. It does that sometimes. After lots of experimenting, I realized it is related with the water heater in the kitchen. When heater reaches at boiling point and starts a loop, transformer starts buzzing&growling. When heater goes off, total silence...

I cannot change the heater because my wife loves it very much.
I accept the pain and when heater is running I'm powering off my lovely F5..

 

[tanwa]

I had buzzing/growling toroid in my F5. Tried lots of stuff and method to solve the problem. Rotated transformer several times, tried dc trap at the input, tried shielding etc.

It is not constant. It does that sometimes. After lots of experimenting, I realized it is related with the water heater in the kitchen. When heater reaches at boiling point and starts a loop, transformer starts buzzing&growling. When heater goes off, total silence...

I cannot change the heater because my wife loves it very much.
I accept the pain and when heater is running I'm powering off my lovely F5..

But in my case, now it is buzzing all the time. So, it hard for me to figure out what is it cause.

In you case that good because when you need heater you don't need F5, or if you turn ON F5, you will not need more heater.

 

[woofertester]

But in my case, now it is buzzing all the time. So, it hard for me to figure out what is it cause.

In you case that good because when you need heater you don't need F5, or if you turn ON F5, you will not need more heater.

Have you disconnected the transformer secondary from the rectifier(s)? I would start there to see if the unloaded transformer buzzes.

 

[tanwa]

Have you disconnected the transformer secondary from the rectifier(s)? I would start there to see if the unloaded transformer buzzes.

I have tried it, Buzzing from transformer reduce a lot. I have to put my ear close to hear it.

And then I connect the Bridge diode, buzzing increase a little bit.

It seem to start buzzing a lot when it connect to filter cap and load.

 

[tanwa]

I check my main AC power wave form, it show the imperfect sine wave in the picture. Is it possible to cause all the problem?

An externally hosted image should be here but it was not working when we last tested it.

 

[basreflex]

if you loop the probe tip to ground with 1 ac secondary wire going through that loop, turn up de scope sensitivity , you could see if there is a lot of current flowing. for example when one diode in the bridge is shorted and the cap is shorting the bridge ac wise

 

[tanwa]

if you loop the probe tip to ground with 1 ac secondary wire going through that loop, turn up de scope sensitivity , you could see if there is a lot of current flowing. for example when one diode in the bridge is shorted and the cap is shorting the bridge ac wise

I have check the diode with multi meter, it is OK thought.