[Kamakiri]

Sometimes having a TV friend staring at something helps you to bring clarity...

Ed: "Okay, but you didn't replace one section of the candohm"

Me: "Right, but it ohms out perfectly"

Ed: "But did you ohm it to ground?"

Me: "Well, no. I usually replace all the sections, but this one tested fine. Wouldn't the value be off if it was shorted to ground?"

Ed: "Don't EVER trust a candohm. Replace that section and power it up and see where you are"

So I did, and now it's got a stable linear picture, and nothing's sizzling. Takes a few minutes of running to get decent AGC and there's some occasional snapping static in the audio (could be a tube socket that needs cleaning), but we'll see if that levels off with repeated 5 minute stints of usage. Have to tweak the adjustments too, of course.

The moral of the story: like Ed said, never trust a candohm......