Checking tubes

[shootingstarno]

Greetings. When my amp arrived in the mail my brother accidently rolled it once as he pushed it along. I noticed it sounds funny lately, to trebly it seems. The amp is a Bugera BC30 combo 2x12. Is it safe for me to check my tubes. It looks like there is a cover I have to take off first. If I take off this cover and turn the amp on, should all the tubes light up. Is that how I could check to see if they are working. I heard someone say they would rap on them with a pencil to see if they rattle one way or another. Any help here is appreciated. Thanks. Paul wa state

[Amp Kat]

You can check them to see if they are all glowing but that won't tell you how they are operating it's just verifying the heaters are all lighting up all the tubes in normal operation. Tapping on the tubes is used to check microphonics and if the amp isn't squealing I wouldn't worry about it. Those amps are quite mid-rangy Imo and when powertubes go bad they usually lose treble not gain it so possibly preamp tube swaps could help you out there.

[g1]

Also try it through some other speakers. Speakers damaged (seized) from being dropped can cause loss of bass.
Or carefully make sure the speaker cones are still moving freely.