How many tubes does this have? It's been so long since I've worked on one...
What a person can do is swap out the 6LQ6's for 31LQ6's if there are 4 tubes, or 24LQ6's if there are 5 tubes, tie all the filaments in series and run the filaments with the 120V AC off the power switch.
Another way you could attack this is to replace the 6LQ6's with EL519's (6KG6A). You'd have to swap a couple wires on the tube sockets to make the EL519's work, but they would work and give you a little more power.
I have done both methods in the past with good results.
Just my .02 worth.
-Exit