[45philcodon]

Curious,

You stated measuring the following voltages:
6F6 output
Pin 2 = 6.26VDC
Pin 7= 17.5VDC
Pin 3 = only 1.15VDC
Pin 4 only 1.41VDC

Relative to ground ---

6F6

Pin 2 should be ~6 volts AC not DC
Pin 7 should be 0 volts (ground)
Pin 3 should be greater than 200 volts DC
Pin 4 should be something greater than Pin 3


Voltages on the rectifier (5Y4G);
Pin 7 = 374VDC

For the 5Y4

There is no connection to Pin 7
Pin 8 should be something greater than Pin 4 of the 6F6

Check your ground connections, something is mis-wired to have voltages so far off.