Mark V Stressing Me Out

Hi-

I have a Late 2012 Mark V. I love it on all three channels. Recently, when in 90w mode, it has started to develop the bad hum of a tube failure about to happen after playing for say ten minutes or so. Yesterday, when this happened on channel three, the hum built quickly and the guitar volume dropped quickly to nothing as well. I ran to check the back before shutting it down and both V9 and V11 were going nuclear together. Do you think that this is the sign of something really bad?

I brought it to the shop, but I'm still stressed about it. Any therapy would be much appreciated.

Thank you!

Sounds like it’s time to replace that set of power tubes.

Replace the powertubes and you should be fine. Mesa supplies matching power tubes. If you can replace both pairs, even better.

Not to add more fuel to the nuclear stock pile, that is the issue I had with the Mark V constantly within the first two months of ownership. New or old tubes would red plate in no time. I will not state what I did to correct this issue as the problem was persistent using the 45W power setting at full power or variac power modes. 90W mode the amp never really went into melt down. Some power tubes are more stout than others. I found the SED =C= 6L6GC tubes lasted the longest (8 months and no red plate vs 20 minute with the Mesa tube). Tung Sol 7581A also held up well. I found there was a bias issue with my amp so I had it corrected. Doubt you have the same issue here as I am sure mine was isolated.

Time to change all power tubes including the Rectifier tube. (just do not forget which one goes where, so swap in the 6L6's first and then replace the 5U4G tube last. It does not hurt to replace the PI tube with a fresh one too.