Metallic clank when playing low E (.22+)

[Milan]

Pulled out an unused Mesa Boogie .22+ from storage (switched over to bass) and tested it out. Works fine, great sound, but when I play an open low E, I get a metallic clanking sound. Does not happen on higher notes. The sound goes away when I turn the Presence knob to 10. The sound is not that loud and is really only audible when playing solo without other instruments.

Would love to get this amp back in perfect shape. Many tubes are MB and might be original. I think I switch out the power tubes years ago. No longer remember.

 

[Neptical]

I'll suspect it's a preamp tube. Same noise happened to me before with my main V1 tube. Changed it out and it went away. Give it a shot.

 

[Milan]

I assumed it was a tube since they are old and the problem goes away when changing the presence.

 

[bigbean]

V2 is the main gain stage just behind the input jack. The only time V1 is in the circuit is when the lead gain is engaged by the foot switch. The presence control feeds one side of V5. If it's old, probably replace all the tubes. One thing cool about this design is that it's cheap to retube (compared to say a twin).

Good Luck!