Burning smell from new power tubes

[Billy Hiwatt]

I put in new Mesa EL84s in my Recto 25. They told me there might be a smell for awhile, but that it would go away as they "broke in".
Well, the foul, smelly, burning odor didn't go away after maybe 20 hours of usage. It turns out it was caused by the adhesive on the little labels mesa puts
on the tubes. I removed the tubes, peeled them off when they were still warm, and then used a bit of rubbing alcohol on a cotton t-shirt to rub away any adhesive that was on the tubes. That solved the problem.

 

[Blaklynx]

I've never seen labels on glass, even for 3rd party tubes. Labels are usually on the plastic base. I use EL34's in a Roadster.

There was no warning / caution notes to remove the labels before installing? If there's no mention to remove the labels, maybe contact Mesa and let them know; more a courtesy call so they can look into it and maybe rectify with a warning label.

 

[deeman]

Hey Billie Largeweight!

I've never seen a sticker label on a tube before, strange.

Who was this 'they' you are referring to?

 

[Billy Hiwatt]

The labels are rectangular, approximately 2"x1/2", and read " Mesa Engineering - handtested in amplifiers & computer matched. 10 AC GRY". "They" would be one of the employees at the Mesa Hollywood store.

 

[Agustín Collia]

It's EL-84's he's referring to, not 34's. El-34's have the labels on the plastic base, but EL-84's don't have a plastic base, they are like a larger 12-ax7, so the labels are on the glass itself.

 

[elvis]

Interesting. I don't remember there being labels on my EL84s. Now I have to look!

 

[ryjan]

Mine are silk screened on and haven't burned or discolored in any way.

 

[tele twister]

I've never seen labels on glass...
...and maybe rectify with a warning label.

Do I sense a QuadaRecto in the future :?: :lol: Okay, bad pun.

But seriously, this sounds like somebody goofed.

 

[Billy Hiwatt]

I can't locate Mesa's customer service email address. The fact that the Mesa employee warned me of a "break in odor" means that this is not a new scenario. They should figure a way around it.

 

[Agustín Collia]

After reading ryjan's post I think maybe they already have, and you may have just got an old batch of tubes which had the labels instead of the silkscreen ryjan is referring to.

 

[ryjan]

I can't locate Mesa's customer service email address. The fact that the Mesa employee warned me of a "break in odor" means that this is not a new scenario. They should figure a way around it.

There are errors in your logic.
The odor they told you about has nothing to do with plastic melting off your tubes. As an amp with brand new components, solder, shrink tubing, and such gets hot and cold a bunch you may smell a slight plastic-y odor. This is normal. Your problem isn't but it should be easily resolved.
I took the tube cage off my amp last night and the EL84's in mine have the silk screened writing and what appears to be a heat shrink like band around the base with the tubes specs. Nothing that would burn under normal operation.

 

[elvis]

+1

There are TONS of chemicals that outgas from the PC Board and other components when heated. It takes weeks or months for this to tail off.

I don't remember ever getting a tube with a sticker on the glass. They get really hot and that would be a terrible idea. I would call Mesa directly. The number is on their website.

Despite the fact that someone at the Mesa store told you it was normal, I would check with the factory. Sometimes people make mistakes.

 

[Billy Hiwatt]

this is a pic of the labels after I peeled them off. The labels were not burning, it was the adhesive. Since I removed
the labels (and the residual left on the tubes with rubbing alcohol), no more smell. And to clarify, there was never any other odor with the amp until I put in the new EL84s.
The reason I put in new tubes was because the previous owner (I got it pre-owned) used it a lot on the 10w setting, which
wears out one tube faster than the other, since only one power tube is functioning on the 10w setting. I only use the 25w setting.