This model is known to blow the outputs for the subwoofer channels. It is a class d amplfier that is kind of pushed a bit too hard. I have seen many of these with bad sub channels. Altec decided they got your money now the product is discontinued. I worked in Altec Lansing engineering dept for over 2 years so i know how they cut costs once the unit gets to market. They changed a few resistor values on that board, took out a few inductors and other components to save a few cents, but get many returns on that model. It originally had lots of hum in the subwoofer due to placing the power transformers very close to the speaker magnets. Best thing i can say is call them up(if they didn't move all those jobs to Honk Kong yet) and tell them of the reoccuring problem and you want a total refund or a brand new(not refurbished marked with a x on the model number) ACS641. Other than that, you might be out of luck.
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