[Greg]

Hi,

I'm guessing the 6S7 was substituted for the 6U7 RF tube.

Sounds like you are the antenna. Do you have an antenna connected? if not, several feet of wire should be OK for now.

If you do have an antenna attached I would check to see if there's a break in the path between the antenna and the grid of the 6S7. By touching the grid you are bypassing the antenna and filter in front of the tube. Does this affect only one or all of the bands?

Look here for schematics if you don't have one. They seem to have clear copies:
https://www.tubesandmore.com/schematics/...-corp/38-2
Specifically:
https://www.tubesandmore.com/sites/defau..._pg8-1.png

The path from the antenna to the 6U5 grid starts at terminal "A" (antenna terminal at top left of schematic) through C1 (band switch) through the selected transformer (1-BC,2-SW1 or 3-SW2) through C12 and to the grid of the 6U7. If something in that path is broken the there's essentially no antenna and no, or very little, signal to the tube. I'm guessing something may be bad in this path for the affected band(s).

Greg