Tubes are still available for the SBE SB2-LA; but, they are expensive. And, unless the unit has been modified for grounded grid operation, the tubes must be matched.
The SB2-LA, and the earlier version SB1-LA, were some of the best "sweep tube" amplifiers produced. They employed six 6JE6 power pentodes in parallel. At the time, 6JE6's where rated at 24 watts plate dissipation and the bunch of them could do about 1000 watts PEP input on SSB. The power supply, which uses a separate filament transformer, was capable of higher power; thus, when the 6LQ6 became available, the amplifier could do an easy 1200 watts PEP input. It will tune the 17 & 24 meter bands without modification; but, is more efficient if the taps on the output PI network coil are changed for those frequencies.
Your letter asked about wiring the sockets for another tube. Unless you have a dozen or more of a particular tube rated for at least 24 watts dissipation, I wouldn't go to the trouble. Check our tube list at the "Power Pentode RF Amplifier Tubes" menu for the "9QL" base configuration and you will see the direct plug-in replacement tubes for the SBE linear amplifiers. Also, I have the schematic - need SASE. - - K4BOV
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