#1
I've got a Fender Rumble 150 that crackles and pops and the sound drops, it doesn't completely lose sound.
I've popped her open and the input prongs are tight against the 1/4 plug, and it doesn't feel like the pots are loose.
I've poked around a little and the connections seem fine, I haven't done too much investigating on the connections, though.
I've taken the grille off and the speaker cloth seems perfectly intact. I haven't removed the speaker to have a look yet, though.
For some reason while toying with it, it was not having any issues with volume turned all the way up. I didn't mess with that idea for too long so it may have just been a fluke.

Does anyone have any suggestions on what this might be, or at least suggestions on what to look for?
Gear:
Fender Telecaster w/ Dual Gibson Humbuckers
Ovation Celebrity Acoustic/Electric
Fender Frontman 212R
Band(s):
Old Too Young (Folk/Bluegrass/Punk)
The Orange Line (Stoner Metal/Punk/Alternative)
#3
Yes. A Squier P Bass and an Ibanez. Different cables as well. Same results.
Gear:
Fender Telecaster w/ Dual Gibson Humbuckers
Ovation Celebrity Acoustic/Electric
Fender Frontman 212R
Band(s):
Old Too Young (Folk/Bluegrass/Punk)
The Orange Line (Stoner Metal/Punk/Alternative)
#5
It's starting to appear as if it's the volume control. Crackling when the knob is adjusted. It doesn't feel loose and I haven't taken the board off yet to investigate pots and such, but it appears that the volume control is the culprit.
Gear:
Fender Telecaster w/ Dual Gibson Humbuckers
Ovation Celebrity Acoustic/Electric
Fender Frontman 212R
Band(s):
Old Too Young (Folk/Bluegrass/Punk)
The Orange Line (Stoner Metal/Punk/Alternative)