Troubleshooting low output, distorted sound

[pdrie]

Having ironed out all of the issues with my Ceriatone express kit, it is time to move to the next project. I have a Fender Custom Vibrolux Reverb that has low output, distorts all the time, and has a slow (once per two seconds oscillation) pulsation to the sound. I have replaced the tubes one-at-a-time and replaced the power tubes. Does anyone have any idea where I should look next? I am thinking that a cathode bypass cap may be bad, but there are probably lots of other possible causes. Any help would be greatly appreciated.

Thanks for all of the great information, and for the time that you all take to share your experience.

Paul

[Allynmey]

What are you tubes Biased at? That amp doesn't come with adjustable bias so measure your tubes to see what it's biasd at. The reason I say this is it is a bias wiggler (Tremolo circuit is an integral part of the power tube bias circuit). I have one right in front of m. The amp comes fixed bias and very cold at that!

[pdrie]

Allynmey,

Thanks for taking the time to reply. The Winged Cs that I just put in are running at 32 mA. I haven't checked the plate voltage yet, but if the plate voltage is close to the schem value of 435 VDC, 32 mA seems to be cold for a 6L6GC (<50% rated dissipation). I need to pull the chassis and check voltages to see just how cold my 32 mA really is.

If I need to adjust the bias, I guess that I have to change the values/ratio of the 2.7K and 18K resistors in the bias supply circuit.
Thanks again for your time and help.

Paul