Mesa Mark V Tube Problem

Mad-Max

Mad-Max

New member
Okay, here's the scoop.

I just recently replaced the power tubes and the rectifier tube in my Mark V. I switched out the 6L6's for EL34's and switched the bias to the EL34 setting. This was mainly just to see what the amp sounded like with EL34's because I heard about people doing that and getting great results, so I thought about trying it for myself.

Got everything hooked up, and it sounded amazing! It felt great to hear my amp again after it had sat for a little while. The one thing I noticed though, was that the tubes were running at extremely hot temperatures, and I saw the caution light was on where the bias switch was. Then I could smell a burning sensation. Nothing melted or anything, I think it was mainly the leather tolex I was smelling, because even with the 6L6's, it had the same smell, but it wasn't as strong.

Needless to say, I turned it off immediately, unplugged everything, and then I tried to research this but nothing really came up. Has anyone experienced this with their Mark V or any Mesa amp?

Any help would be much appreciated!
 
Re: Mesa Mark V Tube Problem

I don't know the Mark V all that well, but with my Recto they say that you should run EL34s with the tube rectifier only, because the solid state rectifier pushes them too hard.
 
Re: Mesa Mark V Tube Problem

Gone_Shootin said:
I don't know the Mark V all that well, but with my Recto they say that you should run EL34s with the tube rectifier only, because the solid state rectifier pushes them too hard.
Click to expand...

How do you run it with the tube rectifier then? The only way I can think of doing that is switching from Pentode to Triode, but I'm pretty sure that's not it.

I think the Recto's have that switch where you can change it to Tube Rectifier mode, whereas the Mark V does not. I think the Mark V already runs the tube rectifier by itself anyway. It always has I believe, and I've never had an issue with this up until I went from 6L6's to EL34's.
 
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Re: Mesa Mark V Tube Problem

Just out of curiosity what valves did you put in?

You cant just bang any old valves in without an adjustable bias mod.

It's clear that your valves are running way too high.
 
Re: Mesa Mark V Tube Problem

I put in Mesa STR 447 EL34's. So they are definitely Mesa Spec.

EDIT: I also did more research and found out that the red light just means that it's in EL34 mode :smack:

But I still can't get over how hot the tubes got. I mean, my 6L6's got hot but they didn't get THAT hot.
 
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Re: Mesa Mark V Tube Problem

Not sure how much help this is gonna be but my Mesa 5:50 has 6l6s and never gets that hot but my old Traynor YBA-1 with 2 el34s would get really hot and smell like something was burning after half hour or so.
 
Re: Mesa Mark V Tube Problem

Mad-Max said:
I put in Mesa STR 447 EL34's. So they are definitely Mesa Spec.

EDIT: I also did more research and found out that the red light just means that it's in EL34 mode :smack:

But I still can't get over how hot the tubes got. I mean, my 6L6's got hot but they didn't get THAT hot.
Click to expand...

Thats all good then. El34s do run a bit hotter than 6l6.
 
Re: Mesa Mark V Tube Problem

That's what I'm talking about! Right there. Is that a problem though? Did it affect your amp in any way? I just want to know if it's safe to run those tubes at the temperature they're at. I don't want to melt anything internally.
 
Re: Mesa Mark V Tube Problem

I apologize for my tube newbie-ness. I guess everything is all good after all!
 
Re: Mesa Mark V Tube Problem

Toe-Knee said:
Thats all good then. El34s do run a bit hotter than 6l6.
Click to expand...

I forgot to mention tion that. The 6L6 bias on Mesas is usually on the cold side, whereas the EL34 bias is anywhere from ideal to hot, depending on where you have the various switches set.
 
Re: Mesa Mark V Tube Problem

Mad-Max said:
How do you run it with the tube rectifier then? The only way I can think of doing that is switching from Pentode to Triode, but I'm pretty sure that's not it.

I think the Recto's have that switch where you can change it to Tube Rectifier mode, whereas the Mark V does not. I think the Mark V already runs the tube rectifier by itself anyway. It always has I believe, and I've never had an issue with this up until I went from 6L6's to EL34's.
Click to expand...

It's complicated with the Mark V.

Channels 1 and 2 have a tube/diode rectifier switch on the back panel ... but it only applies to the 45 Watt power mode. In 90W power it will always use the diode rectifier, and in 10W mode it will always use the tube rectifier.

Channel 3 always uses the diode rectifier - a tube rectifier would be too sloppy with that much gain. Instead of a tube/diode rectifier switch on the back panel, it has a pentode/triode switch that changes the gain structure of the power tubes.
 
Re: Mesa Mark V Tube Problem

SongsForTheDeaf said:
No need to apologize. I worry about expensive amps too! Always ask questions if you are unsure that way you will never damage your investment!
Click to expand...

That was the main concern my friend :)

Just didn't want to potentially damage an amp that I saved most of my hard earned cash for due to me not being as knowledgeable about the tubes. I know Mesa's are extremely picky when it comes to the types of tubes you put in them, so I wanted to make sure that I made the right choices along the way, while still trying to experiment.
 
Re: Mesa Mark V Tube Problem

ratherdashing said:
It's complicated with the Mark V.

Channels 1 and 2 have a tube/diode rectifier switch on the back panel ... but it only applies to the 45 Watt power mode. In 90W power it will always use the diode rectifier, and in 10W mode it will always use the tube rectifier.

Channel 3 always uses the diode rectifier - a tube rectifier would be too sloppy with that much gain. Instead of a tube/diode rectifier switch on the back panel, it has a pentode/triode switch that changes the gain structure of the power tubes.
Click to expand...

That's why I knew it would be different, because the configuration is much more complex with the Mark V, and there are tons of options. I typically have my Channel 3 set to Pentode and then Channels 1 & 2 set to Diode, which is how it came the day I bought it.

Well, at least now I know that everything should be fine. The way I look at it is, Mesa wouldn't have the bias feature on the back if they didn't want you to try to run EL34 tubes in them, especially their own branded tubes. I read online that the Mark V has a tendency to run EL34 tubes a little hotter than some of the previous models, so the fact that they were at such high temperatures makes more sense now. I've just never experienced an amp running tubes that hot before, so that's why I've been proceeding with caution.
 
Re: Mesa Mark V Tube Problem

Mad-Max said:
That's why I knew it would be different, because the configuration is much more complex with the Mark V, and there are tons of options. I typically have my Channel 3 set to Pentode and then Channels 1 & 2 set to Diode, which is how it came the day I bought it.

Well, at least now I know that everything should be fine. The way I look at it is, Mesa wouldn't have the bias feature on the back if they didn't want you to try to run EL34 tubes in them, especially their own branded tubes. I read online that the Mark V has a tendency to run EL34 tubes a little hotter than some of the previous models, so the fact that they were at such high temperatures makes more sense now. I've just never experienced an amp running tubes that hot before, so that's why I've been proceeding with caution.
Click to expand...

Just make sure you have the fan switched on, and plenty of room for air to circulate around the amp, and you should be fine.
 
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