[jcassity]

UPDATE,
had another symptom that i was not sharing with anyone because i did not want to add it to the growing list of odd ball reactions this set was giving us.
I did not feel it was too important and frankly i would have felt bad adding it to the list of things i knew i would need help on. I was greatful to get help with the high level problems i was having, let alone nit pick about minor issues.

Since day one out of the box, with the radio on and sensitivity all the way CW, the volume control was spot on what i would expect.
If i rotated the sensitivity knob slightly CCW, the entire speaker output would go completely down. Lets say that rotating the Sensitivity knob 20deg of its total 320deg range would totaly null the speaker to zero audible output.

I worked on the IF T10 by inserting 240pf caps to remedy the fault of silver mica disease.

I noticed the sensitivity knob still had the same problem and i had a gut feeling this is not the way the factory turned out the radio as new.

i studied the circuit and with some clues Terry gave me a began another adventure down a rabbit hole for no other reason than standing a chance of learning something new.

It turns out what i suspected was correct.

I ordered some pico farad caps from Gary at PTOTP and he tossed in my order some random Automatic Corp IFs (branded as Stag) based on some pics i sent him.
these are NOS Stag brand IF's and the resistance on the pri & sec some were 17ohms and the others were 15ohms.

My orginal T10 IF pri / sec resistance was 9.5ohms. I was assuming this was a correct value but to test my theory on how it affected my sensitivity knob i did some tinkering.

What i know is my other two IF's (T11 & T12) resistance on pri / sec are reading about 15ohms.

the manual tells me that two IF's are the same pn, and the other is a different.
I cant tell by the manual and the actual set which is correct. The manual says T10 and T11 are the same but T12 is different.
T12 resistance is the same as T11.
T10 is pysically stamped with a different pn than T11 or 12. Confussed yet?
dont feel bad, i still am and So is Mr Chuck Dachis the Hallicrafters expert.

I totally tore out all my capacitor test subjects on T10.
I removed the IF completely because i just kept coming back to the idea in my head that i believed something was slightly bad about my T10 inductor windings be it corrosion, wear and tear or just plain ole kaput.

I installed one of Gary's Stag IF's which i picked out to be the 15ohm pri/sec variety.

Like magic, this cured my sensitivity knob response. Now the sensitivity slowly and more linearly adds in what i want to call bass or muffle.

with the old if, barely rotating the sensitivity knob cut out all sound.

now that the IF is totally replaced with a nos type, its working like i "think" it should.