why is my Mesa Dual Rectifier Humming?

[RufioChris581]

i turned my amp on today and theirs a hum i havnt heard before i can turn my volume down on my guitar and turn the gain down on the amp and i still hear it through the cab..i notice in the back of the Mesa head when i turn the fx loop normal nobs up the hum gets worst..is somethign not set right in the back of my head? or what can cause this?

 

[NoGlassNoClass]

Do you have FX pedals in the front end and the loop sharing a common power supply? Try with nothing plugged into the loop. Sharing a power supply between the front end and the loop can cause ground probs. Use a separate power supply for loop FX or use batteries.

Still got hum? Since the FX loop controls seem to affect the hum, I would probably suspect V4 (preamp tube that runs the FX loop). Try changing the tube in V4, if that doesnt work put a known good tube in V1, then switch it to V2 and so on till you find the culprit.

 

[RufioChris581]

i think it might be a ground problem but i switch locations and it still does the same hum...

 

[Boogiebabies]

Good suggestions.

 

[Guitarted]

It's the killer bees nest in the preamp section.

 

[Boogiebabies]

Never had any bee's in the preamp. When you get a quad of EL34's or 6L6's that dont run at -17 volts the amp smokes them out at around 30ma. It's a bad rap for a superb amp due to tube and output transformer warraties.
Just like every other amp maker, they know not everyone is a tube amp veteran so they bias them cold to keep the chuckle heads from blowing them up. Marshall, Peavey and Soldano do this.

 

[RufioChris581]

the humming kinnda stoped..do mesa rects hum when the gain is on 7 or 8?

 

[cnumb44]

Have you ever blown a power tube in the amp while it was running? That happened to me and I lost a screen grid resistor and that caused humming regardless of where I set the volume or gain. Once fixed, it was back to normal.