When your Harman Kardon subwoofer is not working or you have a strange sound in the sub channel that blobs than your power supply needs to get fixed.
This is a easy repair for any DIY.
It contains this components:
2X condensator ( C26 + C5 )
1X condensator ( C30 )
1X resistor ( R23 )
These are the most common to fail due to long standby times of the power supply.
installation is straight forward and easy, the component numbers are on the board.
please check the pictures of the board for reference.