Yes bias is derived from the plate voltage. D 107 converts it into negative voltage and looks like it's dropped along that 100k going to the 220k bias feed resistors. You may have blown the HV fuses. If you put you're red meter lead on pin 3 of the tube socket and black on chassis and you get nada you likely blew the fuse and you should get no neg bias voltage either. You should get oh I guess around 75 volts from that 100k to ground. I'd scrap all those zeners and pit a pot after the 100k and send the wiper to the 220k bias feeds and pin 1 to a resistor to ground. Thats just me though.