[John R]

The 12sa7 goes from a -.7 to -3 (distortion increases) but the 12sk7 is -.7 but the station is muted when I attach the probe and the value stays when I move off the station. I have changed both tubes but no change.
  I do have a signal tracer that was given to me a Heathkit IT-5283 with probes doesn't look like it was used, but have never used it other than as an external pm speaker. looked at the inst online but it was less than clear( can only find a partial manual 9 pages)) to me like is the chassis energized? Hook the black lead to the antenna then probe with the prob with the diode selected on the probe?

Eric,
This site has a 40 page manual for $15. Think I've used them in the past?
John

https://sc2.vom.com/d8/index.fwx?C=MANUALS