Members killart Posted April 2, 2007 Members Share Posted April 2, 2007 Guys, Help. turned on my amp today and had this issue. It's a Mesa Nomad 55 head and has three channels. channels 1 and 2 clean and dirty are fine. sound gorgeous. However, when I kick on the high gain channel(3) I get this helicopter like low drone coming out. Like a pulse of some sort. I can get a guitar signal, but it never feeds back and the volume sucks on that whole channel. Does this sound like it in need of a new set of preamp tubes? Or a larger problem? Link to comment Share on other sites More sharing options...
Members zepman Posted April 2, 2007 Members Share Posted April 2, 2007 It sounds like tubes issues 4-sure and thats a cheap place to start troubleshooting.............John Link to comment Share on other sites More sharing options...
Members zepman Posted April 2, 2007 Members Share Posted April 2, 2007 It really sounds like a powertube to me........... Link to comment Share on other sites More sharing options...
Members Paul J. Edwards Posted April 2, 2007 Members Share Posted April 2, 2007 It really sounds like a powertube to me........... Nah!!! If it sounds good with the clean channel but not on the dirty when you kick in the extra preamp stage than it is most likely the last preamp tube. Make sense???? Link to comment Share on other sites More sharing options...
Members killart Posted April 2, 2007 Author Members Share Posted April 2, 2007 I figured it was a preamp tube issue as it only happens when I kick on the additional gin stages i.e. channel 3. Link to comment Share on other sites More sharing options...
Members potaetoes Posted April 2, 2007 Members Share Posted April 2, 2007 no need to replace all the tubes - you only need to replace the bad one. buy one good 12ax7, and try it in each preamp tube position until the problem goes away. Link to comment Share on other sites More sharing options...
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