[Hallicrafters] ref sr-400 oscillates (to Greg)

[Walt Cates]

I have tried everything in the manual. Here is something different. I don't even know why I tried this. I have a 
clipped tube that I use to match tubes. I put it in and the rig works fine, I get 95 to 145 watts across the bands and the plate dip and power peak match perfectly. The tube gets a little hot at that level, but if I back off to about 75 watts it works fine.

Any thoughts.