I have a slight hum from the reverb in my Deluxe reverb. Pulled V3 and V5 to see if it was the tubes but no such luck. It’s not a real buzz or bad hum it’s just there when I use the reverb and when mic’d up it is annoying. Another characteristic is that when I turn the reverb down or up it adjusts linearly with the pot. Go to zero it goes away, go to 10 it’s loud (never play at that just testing). This is with or without vibrato channel tubes. So, I assume something else is wrong. Tha amp is a 76 DRSF and it sounds awesome otherwise. Any suggestions?