New tubes?

[bluehevy75]

One of the bass heads I've been using is all tube. Around 30 watts and really old.

Current problem: The sound cuts in and out. The sound doesn't cut completely out, but almost. And then it will come back only to cut out again. It is almost as if someone is playing with the volume on the amp or something.

How the problem started:The problem started a couple of months ago. Initially it would just crackle for a little bit and then the sound would come back. Usually as the amp warmed up (after a half hour or so) it would be fine. But over the ensuing weeks the crackling turned into just a volume drop, it occurred more often, and it would happen no matter how hot the amp is.

If this is a tube problem, do I need pre or power tubes?

Thanks,
K

 

[BassmanPaul]

You need a tube tech. It could be almost anything from a bad pot to a cold solder joint.

Paul

 

[RickenBoogie]

+1 Take it in and have it checked out.

 

[seamonkey]

There's a high chance that you'll get a tech that simply shotguns the diagnostic by first swapping the tubes with a known good set.
A bench charge is going to be at a minimal $60-$90hr - where you could just go out and buy another set of tubes first and try it yourself. Tube's do wear - it's documented in all the old tube books and manfacturer manuals that you should change tubes as regular maintenance. It wouldn't hurt to have a spare set.
But you may also need to set the bias which you should look in tube forums and many of the tube sites for how to set it.
And as Paul pointed out - it could be something else entirely.

 

[bluehevy75]

I'll take it in and see what I can learn. thanks for the help.

K