Fender Pro 185 Causing much unwanted sounds

[Samadamn]

Hello people, I need help with my guitar amp as it is causing me a headache. The amp produces a very loud pop when switching on/off or switching between channels, but the main problem is that it makes a loud buzzing sound even with all the volume knobs turned down and nothing connected in. What is causing this I have no idea and need help in finding solutions.
Thank you kind people of forum land

[Enzo]

OK, first look at the speaker cone. When you turn the amp on, does the speaker cone move one direction and STAY THERE? Or does it maybe bump at first but settle donw to about where it was before?

MY experience tells me the most likely problem is the two large main filter caps sticking up from the center of the main board need to be resoldererd.

Ball up your fist and whack the top of the amp. Does that momentarily stop the hum?