[Tubesforme]

Have you checked the ground on condenser 14, the 0.25 mfd between resistors 17 and 18, and that of condenser 16 ? a bad ground on either might be causing your problem.

I originally did rebuilt this condenser block. It has two Xicon .22Uf @ 630V caps inside the housing with the commons soldered directly to the can, as in original Philco cap was and then bolted to the chassis with the original self taping screws. Resistor #17 is a new 470K 1W and resistor #18 a new 100K, that I replaced a second time because the first one read low. Both are new 5% carbon comp type. Capacitor #19, the .01 was replaced a second time, this time with a new Illinois Capacitor .01uf @ 630V. All grounds have been redone as have been all soldered connections to the capacitor blocks. All excess rosin was brushed off every connection. Grounds were also jumped to the chassis with jumper clips when I was testing it. The only part between the 24 detector and the 27 audio tube that has not been replaced is #16, the 250 uuf mica. Tubes have been substituted three times with NOS tubes. All tube sockets were cleaned by hand with a Q tip and Deoxit D5 and tightened. When the 27 grid is grounded or the tube pulled the hum leaves. Pulling the detector does nothing to help the hum. Disconnecting part #19, and leaving part #20, in circuit the hum remains. All of this was done long before I posted on this site for assistance. I do not suspect anything between the detector and audio tube as the problem. Part #21 the interstage transformer was replaced by one from AES, supposedly equivalent to a Stancor A53-C. I wondered if by chance there might be leakage in it. The hum sounds like 60Hz. The voltages on the grids of the 71's is correct. I now have the original Philco speaker assembly and that brought the voltage at point J to the correct value. Bias on the 71's was measured from one side of the filament. Bias on the 27 was measured from its cathode. Voltage on the 27 cathode was measured from the PT, CT. B+ voltages were measured from the PT CT. This response isn't  met to be flippant, I just wanted everyone who has given advice to know what has been done and what didn't work. Thanks to everyone for your ideas.