QuestionQUESTION: Infinity Sound System Model TSS-800. Problem is that the subwoofer intermittently starts humming. Even if we turn off the system. This comes and goes as we're watching television. Sometimes it stops for months, then it will start again.
ANSWER: Does the hum go away if you disconnect the audio cable going into the sub?
IF Yes: The problem is the amplifier still has power, maybe even only standby power and the hum is coming from amp output into the subwoofer. Listen up close to the speaker to determine if the hum sound is coming from the woofer itself or from within the box.
IF NO: From above, determine if the hum sound is coming from within the box or from the surface of the cone of the subwoofer.
Hum sound coming from within the box is probably power transformer buzz. This can be caused from the power transformer loose on its mounting surface inside the box or from loose winding wrappings inside the transformer itself (not so uncommon for iron core transformers).
And since it is intermittent (comes and goes) it is likely such as the transformer.
After considering these comments and you have further discussion, please send follow-up.
---------- FOLLOW-UP ----------
QUESTION: We disconnected the audio cable going into the subwoofer. The hum does go away. Does this mean that the amplifier is bad or the subwoofer is bad? They are covered under warranty and we would like to take them in for repair, but would like to know which piece we should bring in.
Answer
back panel
If the hum goes away when audio cable is disconnected but sub is still ON then the hum is coming from the receiver unit.
From the back of the sub box, if the power is still ON but the audio cable is disconnected it means the sub amp is still connected to the speaker inside the box. Now, if you take the output of an portable cd or cassette or mp3 player and feed in an audio signal from a separate music source you should be able to power the sub (low frequency music will come out) and with that you can verify the amp/sub are operating correctly. If so, this puts the problem to the receiver which has the hum in the signal coming from it.
You may not have to do this separate test if you are certain. You can connect the audio cable again and if the hum comes back then this is another way of proving the hum is coming from the receiver. Understand the concept ok?
Best wishes.
