fender amplifier tube

My guitar tube amp makes buzzing sound?
Whenever I turn on my tube amp it makes a buzzing, humming, whatever you want to call it, sound. It makes the sound when its not plugged in with the guitar and when it is plugged in with the guitar. I have tried pushing in the tubes making sure their tight but that didnt help. I tested the volume and it seems that the buzz noise stays the same whether the amp is on highest volume or lowest. It also seems to make a POP noise whenever i turn it off…… help? By the way my amplifier is a fender pro junior combo amplifier
Grounding issue.
Guitar tube amp power lesson Marshall Mesa Vox Fender Line 6