I have a LSS that I bought new in April 2005. Within the last couple of months I've noticed a nasty harsh overtone on CH2. Last week while I was setting up for a gig, it started to squeal. The cause seemed to be that I had not plugged the FX return line into the pedal board. Plugging it in stopped the squeal, but when I turned the amp off at the end of the gig, there was another squeal as the tubes powered down.
At home, I can make both channels squeal by turning the pots to the max. I thought it must be a microphonic tube. Pulling the tubes one at a time, the squeal stopped when I pulled V2, and again when I pulled V3. It also stopped when I pulled V5, but that only proves it's not the power section. Tapping the tubes produced a lot of ringing on V1, V2, and V3.
I could make the squeal stop if I switched the FX loop out of the circuit. Making me think that the FX (V3) tube might be the bad one. there is also a great deal more noise with the FX loop switched in.
I substituted, one at a time, four old, but good tubes from another amp, first into V2, then V3, then into both V2, and V3. the squeal continued during all of those combinations.
Since I've never changed any of the preamp tubes, I ordered new preamp tubes from Mesa, but I'm not sure that will solve the problem. I've never had this kind of symptom from tubes. Crackle, hiss, popping--I've heard those from bad tubes in my Fender, but this squeal is something new to me. Also new is this unpleasant harshness--not at all like this amp has sounded.
This is my first Mesa, so I'm looking to see if anybody has ever experienced anything similar? Do Mesa preamp tubes wear out this quickly and this way? I've hardly ever had to change preamp tubes in the two Fender amps I have and only then when they start to pop and crackle. Or is this something else in the FX circuit?
The power tubes are about a year old, replacing the originals, which still sounded OK.
I'd appreciate any insight or help that anyone might have. Thanks!
At home, I can make both channels squeal by turning the pots to the max. I thought it must be a microphonic tube. Pulling the tubes one at a time, the squeal stopped when I pulled V2, and again when I pulled V3. It also stopped when I pulled V5, but that only proves it's not the power section. Tapping the tubes produced a lot of ringing on V1, V2, and V3.
I could make the squeal stop if I switched the FX loop out of the circuit. Making me think that the FX (V3) tube might be the bad one. there is also a great deal more noise with the FX loop switched in.
I substituted, one at a time, four old, but good tubes from another amp, first into V2, then V3, then into both V2, and V3. the squeal continued during all of those combinations.
Since I've never changed any of the preamp tubes, I ordered new preamp tubes from Mesa, but I'm not sure that will solve the problem. I've never had this kind of symptom from tubes. Crackle, hiss, popping--I've heard those from bad tubes in my Fender, but this squeal is something new to me. Also new is this unpleasant harshness--not at all like this amp has sounded.
This is my first Mesa, so I'm looking to see if anybody has ever experienced anything similar? Do Mesa preamp tubes wear out this quickly and this way? I've hardly ever had to change preamp tubes in the two Fender amps I have and only then when they start to pop and crackle. Or is this something else in the FX circuit?
The power tubes are about a year old, replacing the originals, which still sounded OK.
I'd appreciate any insight or help that anyone might have. Thanks!
