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Need Advice on How to Eliminate Low Level Hum from Transformer inside a CD Player

If that is the problem, external power conditioners will be of no use and would also be too expensive in combination with an inexpensive CD player. In that case, I would rather buy a different player.
That's not an option at this point, unfortunately.
 
... ok, I don't think it's a good suggestion. But if you try a power conditioner, we'll find out. Please keep us posted on what you do and what the results are. :)
 
I see. Seems like ZHENGXI Isolation Transformers 120V to 120V is the only model available.

I am trying to find a less expensive model from a different brand assuming the isolation transformer would work and I would need to keep it.
 
Is Power Conditioner the same as Isolation Transformer?
Yes, such a insulation transformer blocks DC, so you can see it in a way as a power conditioner. But there are different products.
But such a transformer can also hum. (I am not joking)

Just for the sake of completeness knowing you probably do not have the means: A technician would first check whether the mains voltage actually contains interfering DC components. This can be measured quite easily.

BTW: In addition, such interference does not usually occur all the time. You should then also notice this.
 
It could actually be that the transformer is humming mechanically. Sometimes the vibrations are also transferred to the housing plate, which then acts as a soundboard. If this is the case, only mechanical measures will help. Tinkering skills are required. You can place damping materials underneath, change the mounting, etc.
This. There are internal mechanical forces created in the windings in any transformer. The magnetic fields produced by other windings exerts a force on each wire according to the formula iLxB. There are also forces generated in the core due to interaction of the eddy currents with the magnetic fields, and between the core and the windings.

This is all due to basic physics of transformers. There are internal forces generated that alternate at the line frequency: 60 Hz or 50 Hz, and this can generate audible noise. The windings of the transformers are generally potted in enamel to minimize the motion of the windings, but the whole winding can vibrate a bit on the core, generating noise. Cheap transformers will tend to buzz more due to looser mechanical construction.

This effect does not require a DC current, although a DC current in the windings will make the forces worse. Your transformer just loosened up after being plugged in a while and undergoing a few thermal cycles, and started buzzing.

I can suggest a number of fixes, like taking the transformer out and dunking it in potting compound, but it's really not worth it. Get another CD player. One with an external power supply would be best, for two reasons: you can replace it if it makes noise; and those small supplies are usually switching power supplies that operate at frequencies above human hearing, so only the bats will be annoyed by any buzzing that may be produced.
 
I can suggest a number of fixes, like taking the transformer out and dunking it in potting compound, but it's really not worth it.

I would try tightening the mounting screws first , maybe with a piece of cardboard from a cereal box under the transformer, before putting a brush to work:
 
Looks like an Onkyo C-7030, right?

Since it's lightweight and easy to move around, and the noise is mechanical noise coming from inside the unit (likely one of the two transformers vibrating at 60Hz as mentioned above), can you take it to different rooms in the house - or even to a neighbor's house - and see whether the noise continues each time you plug it in and turn it on?

If so, you might be able to repair it yourself even though you say you aren't capable. It might be as simple as removing the top cover and tightening the screws that hold the power supply board (top left in your picture). Or putting some sort of rubber rings or even cardboard underneath it, then tightening the screws. Of course you'd want to do this with it disconnected from power. Otherwise it's safe and easy to try.
 
This. There are internal mechanical forces created in the windings in any transformer. The magnetic fields produced by other windings exerts a force on each wire according to the formula iLxB. There are also forces generated in the core due to interaction of the eddy currents with the magnetic fields, and between the core and the windings.

This is all due to basic physics of transformers. There are internal forces generated that alternate at the line frequency: 60 Hz or 50 Hz, and this can generate audible noise. The windings of the transformers are generally potted in enamel to minimize the motion of the windings, but the whole winding can vibrate a bit on the core, generating noise. Cheap transformers will tend to buzz more due to looser mechanical construction.

This effect does not require a DC current, although a DC current in the windings will make the forces worse. Your transformer just loosened up after being plugged in a while and undergoing a few thermal cycles, and started buzzing.

I can suggest a number of fixes, like taking the transformer out and dunking it in potting compound, but it's really not worth it. Get another CD player. One with an external power supply would be best, for two reasons: you can replace it if it makes noise; and those small supplies are usually switching power supplies that operate at frequencies above human hearing, so only the bats will be annoyed by any buzzing that may be produced.
I didn't know a transformer would behave this way. It was all quiet when I first got the CD player and plugged it in for testing. It wasn't connected to anything at the time. I just put in on a dinning table by itself.

It was after the CD player was properly connected to a receiver and speakers, and after it was turned on and off a few times for listening that the hum suddenly started for the first time. Since then, the hum would start every time I turn on the CD player. I thought it was caused by either the current going through it or by electrical interference from all the power cables, coaxial cables and speaker wires, etc., or both.

I don't have the skill and knowledge to temper with the components inside. Unfortunately, getting another CD player is also not an option. I am stuck with it, I suppose.
 
Looks like an Onkyo C-7030, right?

Since it's lightweight and easy to move around, and the noise is mechanical noise coming from inside the unit (likely one of the two transformers vibrating at 60Hz as mentioned above), can you take it to different rooms in the house - or even to a neighbor's house - and see whether the noise continues each time you plug it in and turn it on?

If so, you might be able to repair it yourself even though you say you aren't capable. It might be as simple as removing the top cover and tightening the screws that hold the power supply board (top left in your picture). Or putting some sort of rubber rings or even cardboard underneath it, then tightening the screws. Of course you'd want to do this with it disconnected from power. Otherwise it's safe and easy to try.
That I could try but it's the most I could do.
 
I don't have the skill and knowledge to temper with the components inside. Unfortunately, getting another CD player is also not an option. I am stuck with it, I suppose.
How do you think those of us with the skills got them? 95% of the time it's because we grabbed a screwdriver and started tampering. Even those of us with formal technical education developed our tampering skills by just doing it. They don't really teach tampering in school. Nothing tampered, nothing gained!
 
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Really appreciate any advice and suggestions you might have.

Does the player make the physical hum when turned on, but with the lid is removed? Often, transformers placed in that orientation will induce hum in the light gauge outer casework/lid.
 
If you have the skill to remove the lid, assuming you took those pictures, you have the skill to try putting soft, thin rubber underneath the 4 Phillips head screws that appear to be holding the transformer to the chassis.
Just PLEASE make sure the unit is unplugged from the wall, not just turned off.
A good hardware store should have sheet or strips of rubber of varying thickness. You don't need much, a few inches at most. Just enough to float the mounting tabs of the transformer. Don't crank the mounting screws back down tightly. The idea is to "float" the transformer via the compliance of the rubber.
I would try that first before spending any more money on devices.
 
Rather than buy extra gear, why not just replace the player?
 
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