gpuma Posted April 12, 2014 Share Posted April 12, 2014 I tried to swap tubes on my boogie 5:25 and I put in some nos mesa tubes in the preamp (5 12AX7) and some brand new mesa power tubes (2 EL84). The amp was sounding really good but I started smelling a bad smell. I fricked out and turned everything off. Now what? I guess I should put the old jj back in, uh? Link to comment Share on other sites More sharing options...
davesultra Posted April 12, 2014 Share Posted April 12, 2014 Depends on your definition of "smells bad". I know it's not unusual to have a bit of an odor when the tubes are new (I believe it's the paint they use to label the tubes). Don't know that I'd worry, unless it's a real overpowering odor as it usually dissipates over time. The Mini Rect-o-verb that I owned briefly did that. My Marshall Class 5 also has a slight odor that is beginning to fade. Link to comment Share on other sites More sharing options...
slider313 Posted April 12, 2014 Share Posted April 12, 2014 It was probably the power tubes. Put the old ones back in. Link to comment Share on other sites More sharing options...
Vanschoyck Posted April 13, 2014 Share Posted April 13, 2014 Mesa is pretty good about replacing new tubes if they are bad. If I suspect a tube in mine I'll switch back and forth to try and determine what's up. But if the amp is working I figure it's ok until it blows a tube or makes some wrong noise. I've had power tubes blow and it's spectacular - looks like the amp's on fire and it honks loudly for a moment. The worst that ever happened was a resister burned up and had to be replaced. Also, if you call Mesa they will talk you through the situation so you don't feel anxious. Link to comment Share on other sites More sharing options...
Redsand Posted April 13, 2014 Share Posted April 13, 2014 Could it have been the fretboard? Link to comment Share on other sites More sharing options...
tsp17 Posted April 13, 2014 Share Posted April 13, 2014 Could it have been the fretboard? good one. Link to comment Share on other sites More sharing options...
gpuma Posted April 13, 2014 Author Share Posted April 13, 2014 It was probably the power tubes. Put the old ones back in. Yep. It seems the power tubes were the culprit. I'll call MESA tomorrow. Thank you Link to comment Share on other sites More sharing options...
smokedtires Posted April 13, 2014 Share Posted April 13, 2014 Do Mesa's need to be rebiased with tube changes? Link to comment Share on other sites More sharing options...
gpuma Posted April 13, 2014 Author Share Posted April 13, 2014 Do Mesa's need to be rebiased with tube changes? No. Mesa amps have a fixed bias Link to comment Share on other sites More sharing options...
slider313 Posted April 13, 2014 Share Posted April 13, 2014 No. Mesa amps have a fixed bias Actually a fixed bias amp should be adjusted when changing power tubes. The thing with Mesa amps is, they don't have an adjustable bias pot. Picking a set of tubes that run "in the range" is usually a task. It's the cathode biased amps that don't need a bias adjustments as the bias is "regulated" with a large, usually 10 watt, resistor and a cathode capacitor. Link to comment Share on other sites More sharing options...
gpuma Posted April 13, 2014 Author Share Posted April 13, 2014 Actually a fixed bias amp should be adjusted when changing power tubes. The thing with Mesa amps is, they don't have an adjustable bias pot. Picking a set of tubes that run "in the range" is usually a task. It's the cathode biased amps that don't need a bias adjustments as the bias is "regulated" with a large, usually 10 watt, resistor and a cathode capacitor. Of course you are correct. Link to comment Share on other sites More sharing options...
tulk1 Posted April 14, 2014 Share Posted April 14, 2014 NOS Mesa tubes? Sorry, but for the longest time Mesa tubes were known to be the best of the worst. Bought cheap, put them thru their tube smasher, then labeled the ones that survived. Did you know Mesa pre's are now JJ's? Altho' I'm not a fan of JJ tubes, I'd consider that a step up. Link to comment Share on other sites More sharing options...
JeffB Posted April 14, 2014 Share Posted April 14, 2014 Ive put a bias adjustment in my mesa. Its worth it. I understand Mesa's reasoning for the fixed bias but compared to a stock mesa cold bias LS mine is......better I have tried it side by side with two others in store after I put the bias kit in. I can say the same for a Road King, Roadster and most notably a Stiletto, the difference to the Stiletto was the most obvious improvement. I put the bias kit in the LS just after I got it and completely voided the warranty. Im willing to bet I wouldnt have kept it if I hadnt but the bias kit in. Cant remember what tubes are in there now but the longevity of the tubes havnt been affected by biasing warmer than Mesa's fixed bias. The stock mesa LS are biased so cold. Stock they always feel brittle and hard to me. There is a fizz you cant dial out. It sits inside the sound or on top....I dont know. Its fatiguing what ever it is Biased more in line with a warmer fender bias they sound more like you would imagine they would. To me any way. Link to comment Share on other sites More sharing options...
gpuma Posted April 14, 2014 Author Share Posted April 14, 2014 NOS Mesa tubes? Sorry, but for the longest time Mesa tubes were known to be the best of the worst. Bought cheap, put them thru their tube smasher, then labeled the ones that survived. Did you know Mesa pre's are now JJ's? Altho' I'm not a fan of JJ tubes, I'd consider that a step up. So I swapped in the preamp some old jj for some older maybe crappy tubes (JJ or whatever else they used). The amp sounds good with the new tubes. The problem was in the power tubes, Mesa states they are russian so they should not be JJs. And it is not related to the sound at all.... Well, let's see what MESA CS says. Link to comment Share on other sites More sharing options...
gpuma Posted April 27, 2014 Author Share Posted April 27, 2014 the end of this story was a very trivial thing: there is a sticker the MESA testing sticker attached to the tubes that creates this smell during the first few hours. I feel really dumb Link to comment Share on other sites More sharing options...
slider313 Posted April 27, 2014 Share Posted April 27, 2014 the end of this story was a very trivial thing: there is a sticker the MESA testing sticker attached to the tubes that creates this smell during the first few hours. I feel really dumb Better safe than sorry. Whenever changing power tubes, even after a bias adjustment, it's a good idea to let them idle for 10-15 minutes and visually monitor them. An imperfection in the manufacturing process can cause a tube to "red plate" which can cause a blown fuse, smoke a screen resistor or worse. Here's a photo of a matched quad with one tube red plating. That tube would go back for a replacement, if under warranty, or in the trash if not. Link to comment Share on other sites More sharing options...
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