Different voltage of tubes - best practise

[Simon Says]

the right tools for the right job!

Totally. Funny how simple things makes such a difference and comfort of work

 

[Goran Lorencin]

So, a natural follow up ... how are you guys checking when a tube starts to go bad?

I thought I had a preamp tube issue but later pinpointed the hi freq rattle/ring actually coming from the power tubes - with light knocking on the preamp tubes there was always that weird rattle/ring and I was under the impression that all the preamp tubes were suspicious I also noticed that they do differ in the amount of normal ring when knocking on them (Mullard 12AX7 more ringy, JJ 12AX7 or TAD 12AT7 less ringy - probably because of different construction, different size plates), but I have a feeling it is the power tubes that might not be 100% ... also when I crank up my MT15, and if it is close to the cab or on the cab, there is always a slight resonant ring/rattle present.

Should a power tube have any ring or must it be totaly "silent"?

In my MT15 I have Ruby 6L6GCMS tubes, which apparently are quite hard to find where I live. Talking about the same exact model.

What do you think, what are your experiences with diagnosing tubes? Any bulletproof practices or special tools, is it better to use a HB pencil or must I use a 2B pencil for the scientific procedure?

Cheers

 

[RickP]

So, a natural follow up ... how are you guys checking when a tube starts to go bad?

I thought I had a preamp tube issue but later pinpointed the hi freq rattle/ring actually coming from the power tubes - with light knocking on the preamp tubes there was always that weird rattle/ring and I was under the impression that all the preamp tubes were suspicious I also noticed that they do differ in the amount of normal ring when knocking on them (Mullard 12AX7 more ringy, JJ 12AX7 or TAD 12AT7 less ringy - probably because of different construction, different size plates), but I have a feeling it is the power tubes that might not be 100% ... also when I crank up my MT15, and if it is close to the cab or on the cab, there is always a slight resonant ring/rattle present.

Should a power tube have any ring or must it be totaly "silent"?

In my MT15 I have Ruby 6L6GCMS tubes, which apparently are quite hard to find where I live. Talking about the same exact model.

What do you think, what are your experiences with diagnosing tubes? Any bulletproof practices or special tools, is it better to use a HB pencil or must I use a 2B pencil for the scientific procedure?

Cheers

Here’s a decent overview from Mesa Boogie:
https://mesaboogie.zendesk.com/hc/en-us/articles/226488948-How-can-I-troubleshoot-tube-issues-

M/B has their own philosophy on tube circuits, and while it’s been wildly successful, it’s not the only game in town. But the comments on checking tubes are pretty universal.

 

[shimmilou]

So, a natural follow up ... how are you guys checking when a tube starts to go bad?

I thought I had a preamp tube issue but later pinpointed the hi freq rattle/ring actually coming from the power tubes - with light knocking on the preamp tubes there was always that weird rattle/ring and I was under the impression that all the preamp tubes were suspicious I also noticed that they do differ in the amount of normal ring when knocking on them (Mullard 12AX7 more ringy, JJ 12AX7 or TAD 12AT7 less ringy - probably because of different construction, different size plates), but I have a feeling it is the power tubes that might not be 100% ... also when I crank up my MT15, and if it is close to the cab or on the cab, there is always a slight resonant ring/rattle present.

Should a power tube have any ring or must it be totaly "silent"?

In my MT15 I have Ruby 6L6GCMS tubes, which apparently are quite hard to find where I live. Talking about the same exact model.

What do you think, what are your experiences with diagnosing tubes? Any bulletproof practices or special tools, is it better to use a HB pencil or must I use a 2B pencil for the scientific procedure?

Cheers

Substitution is probably the best/easiest method for checking tubes. All tubes are microphonic to some extent, else they wouldn't produce sound, and tapping on them can produce sound through the amp, some positions being more sensitive, the first usually the most sensitive. Many tubes will produce that glassy ringing sound when in use. Some tubes can even develop some rattle/ringing/microphonics over time. I like to use tube dampeners on most of my tube amps, because they reduce the natural ringing, and are preemptive against rattling. I was never a proponent of whacking tubes with a pencil or anything else, a finger nail will do just fine.

 

[shimmilou]

 

[Goran Lorencin]

Oh so that`s how those dampeners are used! I thought that they would go to the base of the tube ... now I get it.

Follow up: I bought a TAD 6L6GC-STR Duet to test things a bit further and must say that I have not figured out much more, it also seems that the Ruby`s are apparently ok. I have found that there was one preamp JJ 12ax7 that was bad and replaced it with a Mullard, all is fine now.
Regarding the TAD vs Ruby power tube sound, the Ruby`s are my favorite, they have a bit more definition and grit, sort of a bigger sawtooth distortion compared to TAD that have more of a finer sawtooth distortion and are a bit "darker", I associate that sound with a synth sound a bit, finer grittiness, more old school Marshall-ish sounding, which I am not a fan of, but could come handy for a different kind of metal sound. On the clean channel the difference was not that pronounced.

That`s it for now. Still have to take time to test the pedalboard, although the Sentry does a good job of taking the noise away when plugged in the front of the amp.