Chris Thompson
Member
Hi, I was wanting to know if anyone on here has ever took a bias reading to see how much current stock Mesa tubes draw with the Lonestar special? I know they are class A and run hot but, I have recently picked up a used one that I am concerned about. I have not had any problems with the 5y3 rectifier tube at all like some have mentioned but, I have had some power tube issues. New Mesa el84's I installed here recently have had an issue with redplating. Two of them redplated at the 30 watt setting after about 1 to 2 hours of gig volume level. I put the amp in standby for a few moments and then back on and they worked fine with no more redplating. I then probed all 4 power tubes in 30 watt mode and I get readings over 51 plus MA per tube with plate voltage around 338 or so. I am not a tech but, I do know enough to get inside an amp safely and have not been able to see anything burned or unusual in side the chassis. I also put the old power tubes in and probed them as well and got similar readings (in the low 50's as well and same plate voltage). The redplating has happened 2 times with the new Mesa tubes. The first time it happened I thought it might be the cathode follower preamp tube because it did have one of the Mesa Russian 2 tubes in there. The volume got distorted and dropped considerably and I wasn't looking behind the amp and didn't see the redplating. When it happened the second time several days later is when I knew it was not a preamp tube issue and looked back behind the amp and found the power tube problem. Anyone who has experience with these amps I would appreciate your input. Thanks