mesa lonestar 1/2 power switching problem

[awalker]

My Mesa Lonestar Classic won't switch to the 50 watt setting on either channel. It makes a farting noise and then cuts out. Sometimes it makes no sound at all. All the power tubes are in working order and at full power it's fine. Any thoughts anyone?

[JimAnsell]

call mesa and ask em.
they cab be pretty helpfull.
the number and hours are on the site.

[Anaconda1126]

Sounds like a blown rectifier tube to me.