[Amps] T'bolt input

[John T. M. Lyles]

Interesting how the Thunderbolt quickly becomes T'bolt online!

The tuned input mode is preferrable instead of the 350 Ohm mode, 
which was made to work with Rangers, Navigaotors, Vikings, Messengers 
whatever they were called. Small tube TX with wide range output 
networks.

If you put it in tuned mode, and drive about 20-0 watts, it gets 
plenty grid I. Use a power attenuator if you must, to reduce drive. 
(see ARRL HB for details, or the manual for the amp). I found the 
screen I meter to be much easier to watch for max drive, while tuning 
the input knob. Another strange thing about the amp was that the 
output loading cap, a switchable bank of micas, has a gap between 2 
and 3 setting, which cannot be perfectly coupled. Like one of our 
caps is off value enough that the switch range didn't cover it. I was 
able to compromise on on or the other range.

Cannot put 50 ohms across the grid where the 350 ohm is, and expect 
to get 50 ohm at input. You could try putting a higher value in 
there, like Rich said, 200 ohm and then use a 1:4 transformer, much 
better idea. But you have to have lot more drive to get the grid 
voltage swing to drive it with 50 across the grid.

73
John
K5PRO