I had this problem on my 902. The repairman diagnosed dry joints on the amp circuit board. You need a strong magnifying glass to look at every joint on the back of the board, especially the power transistors. Look for 'coronas' (a circular crack) round the component pins. The repairman soldered up some of the joints.
A few months later the other channel had similar symptoms, so i did all of them on the whole circuit board. Seems to have cured the problem for the moment. Good luck.
Minor Third, September 2010
