Tube Health in 1988 Boogie Mark III

I have been experiencing some strange behavior with my boogie. It just does not sound as good as it should. I notice that the clean sound sometimes contains a rattling buzz to the notes. I started investigating the problem when I accidentally tap the metal plate on the front of the amp when it was off and could hear an adible metal rattling sound.

I removed all the tubes from the amp and tapped the front plate again and did not observe the rattling. Gentle tapping of the pre-amp tubes identified two that rattle. Gentle tapping on the power amp tubes identified one of the 6l6s. Question should there be any rattle in the pre-amp tubes? Question two, I realize that some rattling of the plate occurs in the power amp tubes but this one is much more pronounced than the other three?

I believe that I should replace all the tubes but I wanted to determine the answer to my rattling questions before doing so.

Thanks.

When tapping the preamp tubes (assuming the amp is running) it is normal to hear the initial tap, but any noise that follows like rattling, sqealing, etc is definately a bad tube.

As regular maintenance, you should change tubes every 2 years at the very least. More often if you play a lot, play very loud, or gig with the amp. When power tubes fail they usually blow the fuse, but sometimes the output transformer will fail as well if the fuse doesnt pop fast enough. Better to play it safe and get some fresh glass in there.