moore 433

My avt 150 is having a problem.
Last night, I went to play it and when it came on , the acoustic and clean channels were fine, but the 2 od channels are running alot cleaner and alot less volume than normal.

Today I replaced the tube in the preamp, but still the same thing. Now at full volume on the master and both od channels the out put is less than half of the output of the clean and acoustic channels....

If anyone has any ideas , I would greatly like to hear them....

Thanks
James.

timstoel

I don't have a schematic handy, but often I have seen the resistor between cathode and ground fail, which can cause the problem you are having. This resistor determines the operating point of the tube and has a direct effect on the gain of the circuit. Because these resistors are mounted close to the tubes, they often get very hot and crack, changing their resistance. Good luck! Tim