[Radioroslyn]

As Ron sez pay close attention to the HV at the plate and screen grid. If low try a new 84 tube. Also measure the grid bias by connecting the + meter to the cathode and the - to the control grid. Should see around -8v or so. Too low grid bias will cause distortion and cause the 41 to draw excessive plate current. I took a quick look at the schematic and see they added a little negative feedback around the 41. The cathode is tied to the high side of the speaker and receives it's ground though the output transformers secondary. This is done to improve the low frequency response and lower distortion.
Terry