Mark IV noise issues

[btown]

I know this topic has been discussed a lot, but I just cant figure it out. My Mark makes a humming sound on every channel, with rhy 1 being the softest and the lead channel being the loudest. It is a recent development; I've been carting the amp to school to record in their studios. It was super quiet before that. I tried changing all the tubes, one by one for the preamp and pair by pair for the power. Could something have jiggled loose? Do I need a cap job or something? I dont think its a grounding issue because I have plugged the amp in other outlets and the hum is still there. Please help...its killing me!!!!

 

[Boogiebabies]

Does it hum with no instrument plugged in?

Have you changed the power tubes?

 

[btown]

Yes, it hums even without anything plugged in. I have an extra pair of power tubes, so I tried repacing them in all combinations, but the hum is ever present.

 

[Russ]

Tube amps make a little hum/hiss on their own. How loud is the hum? How much gain are you using? Be sure you are using a speaker lead for your output. Make sure your output ohms are matched to your cabinet. Try seeking out any rf interference in the room by removing/turning off things like your computer or tv. Also, some lights will create noise in your amp. Make sure there is nothing sitting on or near your amp that uses elsectricty. What else is plugged into your same outlet? There may be something creating noise there or taking up too much current. Your boogie is subject to power quality. Try another outlet in a different room on the other side of your house also. Sometimes an outlet or wiring in your wall may not be good enough. Try the grounding switch on the back. You may want to look at your internals to make sure nothing has gotten loose. Depending on the age of your amp you may just need the cap job. You could try your checking speaker lead too for shorting. If electronics is not your forte take it to get serviced. Discharging a cap can kill you.