My Pultec EQP-1A power supply schematic is shown next. Note: heater connections are not shown. This schematic shows how I wired the Hammond 270FX transformer. The two green (GRN) heater wires connect to all heaters.
12AX7 / 12AU7 HEATERSSince the 270FX heater voltage winding is 6.3VAC, you need to connect the heaters on the 12AX7 and the 12AU7 in parallel by connecting pins 4 & 5 together on each tube. You then connect one green wire to pin 9 (center-tap) and the other green wire to pins 4 & 5.
6X4 HEATERSFor the 6X4 tube, you connect one green wire to pin 3 and the other green wire connects to pin 4. The 6X4 tube does not have a heater "center-tap" pin. The +60V on the green-yellow (GRN-YEL) wire floats 60 volts on the heaters and helps reduce cathode to heater potentials which can extend tube life.
Thanks for reading,