Advise on HQ 110A problem

[N0WVA]

Ahhh! I cant take it anymore! Im actually trying to duplicate your conditions here on my receiver by desoldering here and there. If it werent for robbing you of the satisfaction of figgering it out, Id pay you to ship it here so I could exorcise the demons out of it.

I just dont think the oscillations has to do with the tuned input coils. I would like to say it sounds like a faulty grid leak, but we know its getting bias via the AGC line. Im gonna look over the schematic again.

 By the way, thanks Mitch K9PNP for the schematic.

[N0WVA]

If the front end still squeals, I would try one more thing, just to isolate the situation. Disconnect C8 going to the converter and see if it still oscillates.That would rule out any feedback coming from that tube.

[W3RSW]

But when you clip antenna directly to the stator of the ant. trim cap w/o the 12pf cap it works fine, oscillation goes away, selectivity and tuning are still sharp, on frequency and all is well?

Then your antenna is not loading down or' snuffing' a very high impedance LC, 1st RF amp. circuit.  Hooked directly at the secondary it normally would yield very broad signals, overload, etc. unless it's only a few feet long or otherwise grossly mismatched in impedance.
 
Does the ant. work fine on other stuff?  Is it 50 ohms and used for xmit with other equipment?

"Velly Intellesting...."