PSW125 humming

Options
Good day. I have a PSW125 that recently started humming. It continues to hum even with the subwoofer (rca) cable removed. I moved to a different part of house with no cable attached and still hums. If I lightly tap the amp at the rear the humming cuts out for a moment. Same with twisting the volume knob. Tried switching between on/auto/standby with same results.

Left it powered off for a few days and same results.

What's up? Suggestions?

Comments