so there i was minding my own business basking in the glory of my latest rebuild,listening to the am radio (which i hate) and the set goes dead! i punched fm and all is right with the world,back to am, zip. was my nos ha1138 defective? no all the voltages were reasonable. i probed and fussed all day yesterday to no avail all i knew for sure was if i turned it off for 20 min.'s it would come on and run for a while,tomorrow will be a better day! so this morning i decided to recheck the ic and see if there was much difference in the voltages when it was on as opposed to "faulted out". no apparent difference was noted. i put my finger on the ic to see if it was warm when withdrew my hand i ever so lightly touched f4. atf-020-0 and the set came to life! repeated touching would cause the thing to go off and on. theres no mention of its adjustment in the service manual,but i guess its a ferrite core. i moved the adjustment about 4 degees back and forth and put it back where it was and now i cant get the thing to trip off no matter what i do. i dont believe in magic and all the solder connections are perfect. does anyone have any ideas or comment or know if a NEW f4 can be had any where?