Power Tubes Going Out on Roadster?

[twostring]

I've developed a rather harsh buzzing/grinding sound in my amp. The problem only creeps up on certain notes, but I'm concerned and don't know if it's a power tube issue or a loose connection in the amp. I can tap on each power tube and it causes this static grinding/buzzing noise even without the guitar plugged in. Any ideas?

 

[twostring]

Anyone?

 

[SCOTTY]

Well if you have an extra power tube try switching out each power tube with the new one and see if the sound goes away. Thats a good place to start. Good luck.

 

[twostring]

no power tubes laying about. I guess I've been waiting for an excuse to pick up some KT77s.