The B+ is around 330VDC, and actual plate voltage will be determined by the OPT's primary DCR and plate current.
With the James 6113 / 6115 OPTs and an estimated 56-57 mA plate current (51V across 900 ohms) the plate voltage should be around 305-310VDC, as the drop across the OPT primary will be around 20VDC.
The cathode / filament normally sits around 51VDC above ground reference, so the total plate to cathode voltage is approximately 250-260VDC, which is running the tube fairly conservatively, about 85-90% of its plate dissipation rating of 15Watts - which is conservative in its own right....
With these vintage tubes, it seems apparent that solid-state rectification is not a good idea, unless the power transformer has lower secondary voltage and / or the cathode resistance is increased to 1100 -1200 ohms.
With everything according to the GSG manual, and using the 6AX5G rectifier tube, then 900 ohms cathode resistance gives better performance, and should provide fully safe operating conditions for your 6A5Gs.
It should be possible to run the 6A5G filaments from 6.3VAC, and save on eight SS rectifiers, four caps and two WW resistors, as the cathode should reduce or eliminate the usual DHT AC filament hum problems. Shannon ?
They should still be good adter all these years, if they were gently stored and handled... A little blue glow inside the glass is perfectly normal for these kind of power triodes, either 60 years old vintage or new production Sovtek, J/J, etc.
The "Ike" would run a PP pair around 10-15 watts (check the 6A5G spec sheet). I think the Ike boards are no longer available, but the circuit could be duplicated using point to point wiring. The real name is "eiclone" and the basic schematic is here:
http://www.diytube.com/6B4G_Ike.pdf
The LX-5s are great little speakers, I did the "Black Dahlia" mod to my smaller LX-4s, (bypass the crossover caps to Solen "Fastcaps" and add an indctor for the woofer) and they sound even better.
LX-4 mods:
http://www.blackdahlia.com/tipindex/Tip__3/tip__3.html
Excerpted from the site:
In the end I incorporated three inexpensive mods that elevate the LX-4 sonic report card from a C to a B. I'll describe these for those of you out there who aren't intimidated by a soldering iron.
(1) 0.47 mH air coil in series with the woofer. Pop out the woofer and terminal cup. Pull off the woofer's clip-on connectors and set it aside. De-solder the woofer's yellow lead wire at the terminal cup. Solder the coil leads between the lead wire and terminal cup. Locate the coil under the padding material, which is inside the box.
(2) Bypass the stock cap with a 0.1 microfarad high-grade cap (eg, Kimber or MIT). Solder the bypass cap in parallel with the existing cap.
(3) Insert a small square of acoustic-grade foam into the enclosure directly under the woofer. Reconnect the woofer's lead wires and re-screw the woofer and terminal cup
Some of the ceramic based tubes of the era did tend to get gassy, I have a NOS pair of WE 276As, which start flashing over around 450VDC, so they are not good for much beyond serving as ornaments, lamp bases or possibly the foundation for home made plasma globes Yellow_Light_Colorz_PDT_04
I tried all the tried and true techniques to "burn out" the gas to no avail.
/ed B in NH