LSC driver tube?

[garoflex]

greetings. my lsc is humming, sputtering, crackeling in all modes. tried power tubes, still there. tried preamp tubes two at a time, still there. mesa manual says might be " the small tube that drives the power tubes". is this the 5U4 tube or could it be somthing else? thanx

 

[playdosboogies]

tHAT WOULD BE THE PHASE INVERTER TUBE..PREAMP TUBE CLOSEST TO THE POWER TUBES...

 

[stokes]

The driver tube is the 12AX7 or 12AT7 closest to the power tubes.The 5U4 is a rectifier.The noise could be from any number of things, could be as simple as dirty tube sockets,could be a bad tube.Try rocking the preamp tubes in the sockets with the amp on,in play mode.If you get the noise when one of the tubes is rocked you have found the issue,either a dirty socket or a bad tube or a loose connection in something associated with that tube.

 

[boogiemon]

could also be dirty effects loop jacks.

try the loop bypass switch & see if it goes away.

peace,

 

[ja22y]

I think that the full 100w mode uses solidstate rectifier so if it still sqeals in that mode then the last tube to check is the PI.

 

[garoflex]

thanx to all. looks like the fx loop. bypassed it and all is quiet. acually, i sprayed the jacks with contact cleaner and it worked but it looks like my mxr eq has a problem as the noise is back when i activate it. thanx for pointing me in the right direction