Nomad acting strange.

[zakk615]

Ok, I have a Nomad 45 with EL84 power tubes. I don't know if this is a symptom for a retube as I've only retubed this amp once, but I was playing it today and for a short bit of time, it seemed like the amp was running at half power (as if you were to pull two of the power tubes out). I had to crank the output knob to get the volume up to where it would normally be. So, I looked at the tubes, they appeared normal. The sound was awesome: I was getting much more power tube distortion then normal. But I was wary to keep on playing as I didn't want to break the amp. Then I switched the Standby (high volts switch) on and switched it back off and the amp goes "back to normal." I then had to lower the output knob to not break my eardrums.

I've had this amp for a good 3 years and never had experienced this. Last time I had to retube, the amp was making these "farting sound" noises, so I don't think the tubes are the issue. However, I guess there is a possibility that there may be something wrong somewhere internally. Has anyone else experienced something like this with any of their amps?

 

[no soul]

definitely sounds related to your power tubes.
Having to turn the output up and getting more distortion is powertube related. If I were you Id go ahead and retube the powersection just as a cheap way to isolate the problem. Worst comes to the worst, if the retube doesent help at all, at least you have some extra power tubes.

 

[mesa115]

My Nomad 45 did this about 2 months ago. The volume would cut significantly in the middle of playing. When switched to standby, then back, the volume would return. I did this for about a week, then the switch to standby didn't help.

I replaced the power tubes, very inexpensive really, with matched pairs, and the problem completely went away.

I bet this fixes your problem.

 

[cvansickle]

I had the same problem with my old DC-5. It used to eat tubes like Linda Lovelace!

Mesa115's standby switch solution would work, but it's impractical while you're playing. The problem went away with a new set of tubes.

 

[zakk615]

Ok, so it's just probably about time to replace the power tubes again. Thanks for your help guys!

Also, I've been wondering this for quite a while: Why is it on the Nomad that the Standby switch is called "Hi Volts"? Is that just another name for standby?

 

[Nomad]

EL84 Power Tubes dont last as long as say 6L6's. If you get a year out of em your doing good. Try to get some good Tubes IE JJ's or something like that. Dont get no real cheapos.

 

[zakk615]

EL84 Power Tubes dont last as long as say 6L6's. If you get a year out of em your doing good. Try to get some good Tubes IE JJ's or something like that. Dont get no real cheapos.

Yeah, I've actually been considering getting JJ's from Eurotubes.com. I read about them at the site and judging from the reviews (from here and other sites), they seem like good tubes.

 

[Nomad]

JJ's are good tubes. The nice thing about EL84's is you dont have to worry about biasing them.

 

[TheRazMeister]

JJ's are good tubes. The nice thing about EL84's is you dont have to worry about biasing them.

Actually Mesa's are fixed bias so as long as you don't switch from 6L6's to EL34's no re-biasing is necessary.

 

[Nomad]

Yes and no. You cant just throw any old tubes in there they have to meet a standard.

 

[Nomad]

In other words as I understand it. Mesa says the tubes used in thier amps must meet a certain set of parameters which they claim they test for. If you buy thier tubes these meet those qaulifications. If you buy a set of crappy tubes and throw them in the amp you may suffer consequences from that.

It could end up anywhere from a very cold bias to a very hot bias to something as crasy as a shorted tube which tends to reek havick on amps.

 

[Nomad]

I use the Mesa STR430 6L6 tube almost religiously. I have had very good luck with these tubes.

I do have a little SDG Vintage Tweed Proluxe amp with JJ's in it though. The guy that built it for me got me a matched Sextet of the JJ's to which the amp is biased for. So I wont need a bias for a while.

I havent had much luck with some of the preamp tubes though. Dont know why.

 

[TheRazMeister]

I called TheTubeStore.com and spoke to the resident Mesa expert and he says that the vast majority of Mesa owners order the SED Winged C (Svetlana) 6L6's. That's what I'll be trying next. As stated by Nomad, you have to get tubes intended for the brand of amp you have but in Mesa's case there is a wide range of quality tubes that will work.

I use the Mesa STR430 6L6 tube almost religiously. I have had very good luck with these tubes.

I do have a little SDG Vintage Tweed Proluxe amp with JJ's in it though. The guy that built it for me got me a matched Sextet of the JJ's to which the amp is biased for. So I wont need a bias for a while.

I havent had much luck with some of the preamp tubes though. Dont know why.

 

[Nomad]

You should see my box of tubes. Maybe I should take some pics. I'm working on my lifetime supply. I've got a bunch of 6L6's and everything else. Cant have enuff Toobs.