[rck46]

I am getting low volume on this radio with the volume control turned all the way up when tuned into a very strong local station.  I have gone through this radio and replaced all the electrolytics, paper caps, some of the micas, and out of spec resistors.  All the antenna, RF, oscillator, and IF coils show continuity.  In the process of aligning this radio I noticed that I could not get the secondary of the 1st IF to peak no matter how much I turn the adjusting trimmer screw.   I took the cover off of the IF to see if there was anything obvious and noticed that there is a black wire that makes one wrap around the secondary coil between the third and forth windings.  Here is a picture of the IF.  The top coil with four windings is the secondary coil and you can see the black wire with some of the insulation flaking off.
 
One end of the wire goes to chassis ground and the other end attaches to pin 5 of the 6K7 I.F. amp tube.  I see nothing on the circuit diagram that indicates this.  Circuit diagram is at http://oldtech.net/Philco/37-630p1.gif.  

Any ideas as to the purpose of this wire and if it relates to my problem of not being able to peak the secondary of the 1st IF and low volume?

Other things I have tried or checked.

1.  Voltages check out reasonably against those listed on Riders, page 7-59.

2.  Subbed tubes - no change.

3.  Get loud hum when touching grid cap of 6Q7 tube.

4.  My shadow meter is open so I subbed a 1500 ohm, 1/2 watt resistor to replace it.

5.  I noticed I get somewhat louder reception when a gound is connected to the gound terminal on the back.

Two more questions.  The circuit diagram shows the aerial and ground terminals.  Is the antenna to be connected to the red or black terminal or does it make any difference.  Also there is a link attached to the ground terminal that can be swiveled between the black terminal and terminal 4.  What is the correct position for this link?

I also posted this over at the antique radios site.


Thanks, Bob