[rfeenstra]

One side of the filament of all tubes except the rectifier is tied to chassis ground.  The other filament pin runs from tube to tube and ultimately is tied to one of the wires of the filament winding of the transformer (at your "2" in the pic).  The other side of the filament winding is tied to chassis ground along with pin 7. Your pic shows that. Measuring from chassis to one of the filament pins (pin 7) will give 0 volts AC.  From chassis to the other should give somewhere around 5.8 - 6.3 volts AC (pin 2) as you indicated.  If the tubes and pilot lights are lit, then that part of the transformer is good and the wiring is correct.  What is the plate to plate AC voltage on the rectifier (careful, probably is nearly 600 volts AC without the rectifier in the circuit)? Also, what is the DC voltage at the positive terminal of cap 120?