2. misc-audio
  3. 1170020061

how do you know a bad tube?

I'm thinking of winding up all or at least mostly with tube gear. that said, how does a person know for sure which tube device needs a tube?

By that i mean, if you have multiple preamps, and amps, then I'd see it as not a lot of trouble determineing which one has perhaps an issue. but if you only have one pre and one amp both with tubes and things begin to sound funky, how then do you tell which unit is the culprit?

Past that then, how do you know which tube? (given there aren't any indicators on the chasis, and the tube itself isn't dead blown). ?? ...and apart from having on hand dupes of all the tubes in the system.

I am overlooking the obvious here for a reason. I'd as soon not have to get a tube tester. Unless there is a mighty simple one to use which has an oscillator in it as well as meters.

Sorry if it is a dumb question, but sure seems like a simple answer here will come in handy later on... as I'm looking for an "in house" solution that ain't way expensive and is simple enough tactilly for me to use.

thanks much
blindjim

Showing 2 responses by newbee

newbee
4,809 posts
 
The simplest way is by simply switching tubes from left to right channel and vis a versa using a process of elimination. For example you have four tubes in a pre-amp. You move the two on the left to the right side and the reverse. Nothing changes. Likely then that isn't your problem. Then you move on to the next component (amp) and do the same thing. Let say the problem changes channels. Now you move one of those potentially bad tubes back into the other channel in exchange for a known good tube - if the problem moves that is the bad tube. If it doesn't move the one you didn't pull is a problem.

Different problem, different solution, but that is the easiest way to isolate a bad tube for newbies. You don't need a tester, just ears and a little logic.
newbee
4,809 posts
 
How ironic the timing for a personal delima. Last nite I turned off my pre-amp fist and got a right side pop in my speaker. Since I hadn't turned off my amp 'it had to be as a result of something in the pre'.

Switched tubes from side to side as I had suggested. No change! Then I went to the amp and switched one of the sets of small tubes. Not only did the pop leave the right channel it left the system (for now anyway). If I had a tube tester I could probably test it and detect some imbalance that I can't hear in use. I'm not sure if that is a loss.

Back in the days I was frugal and thought my tubes would (should) last forever I had a spare tube of each type set aside for testing. Then when I changed tube sets I had lots of tubes available for testing as well as spares.

My biggest fear about owning a tester is just imagine how anal you could get about tube condition and how much time you could spend monitoring their condition. Oh, my. Got enuf on my plate worrying about things like set-up etc with out taking on that responsibility.

Have fun, it ain't really a big deal. I am as dumb as a stump, even if I don't appear to be so sometimes. :-)
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