Chosen Solution
I have a vintage Marantz 2220B receiver. There is a hissing sound coming form the on/off knob. The sound last for about four minuets and stops. I produces sound for the unit the display panel light dim for time to time.
brn, Unplug receiver, take the cabinet/cover off component to access switch, check to ensure switch has good connections, spray switch liberally with electro contact cleaner while working switch. Check connections for the lights while apart also. Good Luck. I hope this helped you out, if so let me know by pressing the helpful button.
