Could I add in series to the two 0-250V 0.8A parallel the one secondary 0-48V 0.1A to increase the voltage to 298V 08.A? I have on hand cap 820uF 550V.
No. You can only add in series different voltage secondaries. In that case the voltage will be good but the weaker ones are the current limit. I.e. 80mA * 0.63 bridge DC mA derate to 50mA. You could add in series the 48V to already paralleled 250V though. But don't play with transformer without dim bulb tester and disconnected from PSU.
No Salas, I want to paral·lel the existing one 0-250V 0.16A and add in series the 0-48V 0.1A one to have 298V máx. 0.1A if 0.1A * 0.63 = 63mA is enough?
But there is something not ok with the PSU isn't normal to have only 310V from an input cap with a bridge, 250V x 1.41 = 352V....
Its usually less, about x 1.3 with losses from not too stiff a Tx and diodes
Better I will order a custom new one, enough 250V 0.2A or may I ask more volts & mA seen what's happening with Lundahl?
I have only few times used Lundahl step-ups for MC carts, and OPT for medium power push pull tube amps. I don't know about their power transformers.
With CCSed reg loading can happen on so so regulation % Tx especially when pushed near max DC mA spec
The 0.1A secondary now is the weaker link so 63mA DC after full bridge derate as in their datasheet note.
Making cables short and tight & grounding the caps at the filaments reg.
What Raw DC and B+ you ended up with your now power transformer? What type of new one you ordered? How does it play now that you can listen better without any hum? Picture with final hum-less wiring arrangement would be nice to see.
