Q: Fastest Way to Detect Bad Tube

[audiometallicaslave]

So after only 1 month with my new dual rec, I was playing on ch. 3 and the gain just disappeared on all channels.

1. What's the best way of detecting the bad tube that caused this total loss of distortion?

2. How long do the stock Mesa 6L6s last (generally speaking) if one follows the cold start up procedure (i.e., power on, wait a few mins, standby on)?

 

[Brewski]

1. What's the best way of detecting the bad tube that caused this total loss of distortion?

That would be one your pre amp tubes. If you have a spare tube, you might want to try switching them. That's one of the quickest ways to determine whether a tube is doing it's job or not. You can also try tapping on them lightly with the erasure end of a pencil. You may be able to hear a bad tube, if it's microphonic.

2. How long do the stock Mesa 6L6s last (generally speaking) if one follows the cold start up procedure (i.e., power on, wait a few mins, standby on)?

Rule of thumb, generally about a year to a year and a half and preamp tubes should go around 2 to 3 years. You're mileage may vary, depending on how hard you're driving them. Tubes can be a quirky thing you may get more or less time on them. It would be a good idea to have a spare or two, especially, if you're actively gigging.

 

[no soul]

pre amp tubes can vary A LOT.

Examples:

I have a 1966 fender Bassman, which has its ORIGINAL preamp tubes in it.

Then I have a 2001 single recto head, also with its original pre tubes.

And last, I have a F100, which I bought a year ago used, and retubed, and blew a pre tube just a month ago.

and for reference I play the recto the most. But they say combos eat tubes quicker...

p.s.

there are so many variables though.
How hard you play, how long you play, and even what the electricity from your wall is acting like!

 

[audiometallicaslave]

p.s.

there are so many variables though.
How hard you play, how long you play, and even what the electricity from your wall is acting like!

It's interesting you mention electricity. I have a suspicion a preamp tube is not fried. I think the loss of distortion could be due to inconsistent electrical flow from the wall outlet. I'm not a tech-person, but is that a possibility?

I plug my DR and 2x12 cab into a power surge protector. I run all my effects pedals through a pedal board with furman power conditioner, as well as my rack gear. I might try to get a better surge strip or plug the amp straight into the furman-powered pedal board.

Agan, I'm not sure if electricity has anything to do with it, but it might be worth looking into.

 

[scubamegadog]

Going for the record on valves (tubes?). I have just changed the 6L6s in my Mrk 1 for the first time since 1981 - and that was when I bought it used.