Crackle in full power mode when warmed up

[TimF]

After playing for maybe an hour, my Mark V starts to crackle. I notice this is in Full pwer mode, at 45W or 90W. The problem goes away if I switch to Variac power or switch to 10 watts.

Any thoughts what the problem is? If it seems like power tubes are the likely culprits, which ones?

Thanks,

Tim

 

[>Photi G<]

If it's in both 45 and 90 watts, then the Outer pair of power tubes need to be replaced.

 

[Gunner]

Tim,
I have the same issue. I called Boogie and they suspected a preamp tube. I bought a new Mesa 12AX7 and one by one swapped out each preamp tube and the crackling persisted. My Boogie is just out of warranty for the tubes so I guess I will bite the bullet and buy a new set of power tubes and a rectifier tube and swap those out. On another note, rumor has it that serial numbers 4000 and above have received some updates such as better screenprinting on the faceplate, new reverb tank, and some cap and resistor changes affecting channel 3 for the positive. My screen printing is coming off so I contacted Mesa and they said to call and get an authorization form to send it back and they will replace the faceplate and try to diagnose the crackling. Good luck!