Humming Toroid Transformer

[Mike]

Hello,

I have an older set of Altec Lansing computer speakers from an old Dell. They haven't been used in a long time (about a year) and I hooked them up recently to my computer to replace a dying set of Boston's.

They function perfectly, they sound fine and everything, but there is a noticeable humming coming from the transformer that I do not recall occuring before.

The humming is easily heard while sitting at the desk over the noise of the computer and with the subwoofer on the floor. It occurs regardless of wheather or not the speakers are on, becasuse with this design the amplifiers are constantly on but just get put into standby.

It's not that its annoying to me, as I can barely hear it only with no music playing, but I'm just worried about this possibly causing some sort of issue, such as a fire hazard.

Nothing is causing any sort of magnetic interference, they have been used at two seperate different homes in 3-4 different rooms, so the problem is definately inside the circuitry somewhere. I have not had the chance to take out the amplifier to inspect for any failing capacitors or otherwise visible damage.

I'm mainly concerned that this may pose some sort of fire hazard, and at the moment am avoiding leaving them plugged in.

Thanks,
Mike[/code]

[dacflyer]

all power transformers humm at some sort of level, and depending on the load. if all is well in operations, you probably have nothing to worry about, as everything is normally fuze protected, unless its been tampered with. so if the transformer were to short out. a fuze would quickly blow.
so there should be no worry of a fire hazard..

[Bigglez]

Greetings Mike,

I have an older set of Altec Lansing computer speakers from an old Dell.

We have two sets of something similar if not the
same in our office.

there is a noticeable humming coming from the transformer that I do not recall occuring before.

I take that you have two desktop speakers and a sub-woofer
on the floor? Left speaker is plugged into the Right speaker,
which has the controls and a thick cable to the sub-woofer?

It would be worth your piece of mind to open the box and take
a look. A mains related hum could be mechanical (transformer
laminations loose), or because the transformer is under
abnormal load stress. The safety fuse in the mains will
save you from fire, the transformer may have a cut-out
(thermal fuse) or other means of over temp protection).

Fixing it now would also save the entire system.

Comments Welcome!

[Robert Reed]

Mike
In regards to your hum, it may be acceptably normal or maybe a partially shorted turn in your transfomer putting an excess load on it. Is the transformer hot to the touch? The safety fuse may or may not protect this device from a fire.
Case in point :
Years ago (in the tube days) I had just purchased a Lafayette component stereo system. Several weeks later in a dimly lit room and at night , I was listening to some music from the FM tuner section when all of a sudden the audio went dead.
What could be wrong. A quick glance across the room and the power amp pilot was still lit, the fm tuners dial scale was still lit. Upon looking at the tuner closer up, Its dial light had a flicker to it. Closer still - my god, its on fire!After unplugging and opening up the unit, it was evident that the power transfomer had caght fire and was supplying the dial light. Apparently it had heated up to the flammable point while still mantaining a low enough current to keep the fuse intact. A rare occurence, but I've never forgotten that possibility.

[haklesup]

What kind of transformer are you talking about. Something built into the speakers or is it just a plain old wall wart making noise. If so, just get another or swap with something else you don't care about hum.

If the transformer is built into the sub-woofer, you should silence the sub with your finger to make sure it is not coming from the speaker.

Sometimes you can silence a humming transformer by pressing on it with your finger, if you are lucky enough to find a sweet spot then you might be able to apply RTV to silence it permanently.

"Years ago (in the tube days)" Did this pre-date the UL listing?

[mojorizing]

What a coincidence, just last week I looked into the cause of the 60hz hum in my Altec ACS495 subwoofer. This came with an old WIN98SE Dell desktop, and they sounded great for a few years. Then I upgraded to XP, and there was no driver for them, so I lost the GUI for them, but I continued to use them with the manual volume knob on top of the right speaker.

Then I noticed a hum coming from the subwoofer, even with the sattilite speakers unplugged. This hum was coming from the speaker, not internally as from the transformer. I opened up the case and scoped out the power supply, which just consisted of a toroidal step-down transformer, and bridge rectifier, electrolytic filter caps. Nothing fancy. This powers directly a KIA6210AH http://www.alldatasheet.co.kr/datasheet ... 210AH.html
Amplifier. What I saw was a ripple on this power supply going to this amp, and what I did was solder replacement electrolytic caps in parallel with the existing caps. This didn't clean up the ripple. The inputs to the amp were clean and noise free. I'll probably look at it once more before I heave it into our local landfill.

[Mike]

Thanks everyone for the replies!

Sorry, I should have clarified further at the beginning.

The speakers are Altec Lansing ACS295. They have a built in toroid transformer. The transformer is always powered on and the hum is the same wheather the speakers are in standby or powered on. I cannot tell if it chages with more dramatic load such as the volume turned up as the hum is inaudible over the music. Also, it is definately the transformer, not the speaker.

I'll see how warm the transformer gets. Right now it has not been powered on long enough to actually warm up, but I'll report back after they have been plugged in for a while.

Thanks again for the help,
Mike

[Janitor Tzap]

Thanks everyone for the replies!

Sorry, I should have clarified further at the beginning.

The speakers are Altec Lansing ACS295. They have a built in toroid transformer. The transformer is always powered on and the hum is the same wheather the speakers are in standby or powered on. I cannot tell if it chages with more dramatic load such as the volume turned up as the hum is inaudible over the music. Also, it is definately the transformer, not the speaker.

I'll see how warm the transformer gets. Right now it has not been powered on long enough to actually warm up, but I'll report back after they have been plugged in for a while.

Thanks again for the help,
Mike

Mike,

If It is just the toroid transformer.
You could try epoxying it in slow drying epoxy.
I've done this with several Flybacks and Horizontal Driver Transformers.
As well as Deflection Yokes.
And it worked quite well for me.

Have you powered the speakers on with them disconnected from the computer?

If not...
Try it and see if you still have hum coming from the speakers.

No?
Then I would say you have a ground loop problem with the sound card in the computer.

Yes, the hum is still there.
Then it's a filtering problem in the speakers power supply.

Either of the two can be hard solve.

Thou, if you have another pair of speakers to try.
Hook them up and see if they also have the hum.
Yes?
Ground loop problem with the computer.
You could try an Ground Loop isolator, but that could get spendy.

No?
Bad Filtering in the Altec Lansing speakers.
You can try fixing them, or just replace them.


Signed: Janitor Tzap