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
newbee
4,767 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.
montytx
138 posts
 
Depending on what kind of tube failure you are experiencing, you can sometimes get a good idea by simply looking at the tubes closely.
blindjim OP
3,092 posts
 
Newbee
Well I sort of got that bit all by my lonesome, but it's good you pointed it out. ...and if you have but one tube and no twin? (several tubes, two singles, different types: and one type is pairs)??

Montytx
Thanks. perhaps you missed my handle, and refference to an oscilator (audible indicator), but thanks anyway. Although, unless one is familiar with the tube archetecture beforehand, past the obvious, what could one hope to glean?
Maybe I missed your point.

if there are same/same tubes on either channel, certinaly one can swap back and forth. Sure, if a tube won't light up.. yep, it's dead. There are tube components that do not duplicate the tubes within it throughout its design.

Then what?

In that case there is no other tube present to swap about within the unit. That scenario happens to be the case in an upcoming unit for me, so I thought it may well be also the way with the possible amp (s), therefore I thought to avail myself of some greater experience, or unbeknownest to me, device or method, before the fact.

it would seem at this point only having exact same spares or a tester, is the ticket... and/or at least an inexpensive integrated with pre outs and main ins, or a couple of real budget pre & amp pieces about just in case.
More to discover