it's the configuration for LL1623 3k ultralinear 50%?
are pins 1 and 8 of the EL 34 connected together and connected to the 31v auto bias?
yes, 1 and 8 connected at the tube socket, and connected to the auto bias resistor
what 'is voltage and amperage of the secondaries of the power transformer?
LL1650 has 2 secondary to 173V 0.63A to be connected together, is that right?
346 V AC, 0,63 A
3 secondary 6.3V are used for the tube filaments: it's the last one unused?
yes, not in use