[MrFixr55]

Hi John,

I don't have this radio, but I can supply some info:

Based on your pic, pins 7,8 and 1 are used together, go to the wire in question and are also grounded to the sub-chassis.  This would be correct for the 6A8 as pin 7 is one leg of the heater, pin 8 is the cathode and pin 1 is the shield for metal or coated tubes.  For the non-coated glass tube, Pin 1 has no internal connection in that tube. The fact that pin 1 is grounded and a glass tube is used does not have a negative effect. However, if the tube does not have an internal shield, an external shield must be used if called for.

Attached is a base diagram for the 6A8 and 6A8G from the RCA Receiving Tube Manual RC14 (ca 1940).  
   

In the RCA Receiving Tube Manuals, the pin numbering is from the chassis side (worm's eye) view.  Where the ground is connected is important in an RF section, since, I believe, that this is sub-chassis is mounted to the main chassis by rubber insulators. However, since the pins 7,8 and 1 of the 6A8 are already grounded to the sub-chassis, this may make where the ground wire is attached to the main chassis to be less important. It seems to me that this should be connected to whatever filament lug is grounded for the 6K7 IF tube or whatever tube supplies the "hot leg" 6Vheater voltage to the sub-chassis.  I cannot tell from the schematic whether pin 2 or Pin 7 of the IF tube is at ground potential. Pin 1, the shield of the 7K7 IF tube is grounded or should be, especially if a metal or Zenith (Sylvania) Metal-Glass (their brand for a glass tube employing internal shielding) is used.  The cathode, Pin 8, is not grounded like the 6A8; there is a cathode bias resistor and a bypass condenser.