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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
capt369
152 posts
 
Blindjim. I think others have addressed your tube dilema very well. I`m curious, after reading your "what would your next upgrade be" thread on your system page, what your impression of Herbies tweaks is and how you`re doing with the room tuning.

I`m a big "Herbies" fan and have implemented (one at a time) every dampening tweak that Steve offers. Each implimentation isolated instruments more and more and brought a more realistic soundstage. I`m very happy with the results.

I`m also doing some room tuning and am curious as to how you`re coming along with yours. Maybe you could update your other thread (if you feel like it). It was an interesting read for me, and I assume, others.
larryi
3,804 posts
 
I don't know of any kind of simple and cheap tube tester that will reliably tell you when a tube is going bad. Most testers are not cheap and many require calibration and maintenance.

Also, a tube can begin to go bad in ways that certain testers will not be able to detect. Even a good tester that measures transconductance, may give you an idea of the strength of the tube, but not other conditions, such as noise. I had a small signal tube, an EH 6sn7, that became gassy. It tests spectacularly strong for transconductance, but my tester (not cheap) also tests for gassy condition and it showed that this tube was horrible in that respect.
blindjim OP
3,092 posts
 
Capt369
i apologize for not promptly or even regularly giving some followup there. i will.

Larryi
yeah. i was just hoping aginnst hope, I had overlooked something easy, or some other fashion or method going forward to check things out. if I do wind up with a pair of tube mono blocks as well, and something goes awry, I'll have a coniption fit trying to swap in and out tubes from a second set as was mentioned previously... but is a good idea. one I have followed in the past. one also that is a mite pricey. As I chose then to get them all from reputable dealers and none have actually gone bad on me Save the first set i got which came with the preamp, but were disposed of shortly thereafter. man. if there is anything I hate to do it's trash a tube that still lights up, and it is tiresome and expensive to send them out to have checked. Not to mention the waiting period (s).

OK. A second set instead of a tester. Super.

Does anyone make one tube monos?
entrope
482 posts
 
What is cheap for a tube tester compared to a second set of tubes at today's spiraling prices or damaging a component with a bad tube?

I found a Sencore Mity Mite VII for $100 without looking to hard. But even at $200 or $300 if you have a long term commitment to tube gear then it makes sense to have one.
blindjim OP
3,092 posts
 

Entrope

yes, $100 - $300 is cheap. I'd have no issues going for something like that. My concerns, are it's use. meter/display size, and calibration needs... doing twin triodes, large power tubes, in all, it's flexibility and naturally it's accuracy.

meters/displays need be of substantioal size for me. Figuring it out is not much of a problem there after. although I appear dumb as a stump sometimes, i don't believe I really am.

Waht resource sells these things?
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