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
