[Johnson] Invader 2000 Grid Current

[WQ9E at btsnetworks.net]

The big problem with the Tbolt is the low (2,000 volt) plate voltage which forces the 4-400A final into AB2 to reach the 2KW PEP rating.  My Heathkit KL-1 (same basic 4-400A circuit) but with 3,000 volts under load runs class AB-1 to its 2KW rating and even my little Yaesu FT-817 will push it to almost 2KW PEP.  Johnson also used the same relatively low voltage for the Invader 2000 and it has the same issue as the Tbolt when driven to the old 2KW rating.  The Invader 2000 looks pretty ugly on a spectrum analyzer when approaching the rated 2KW input.

Depending upon the life left in the Tbolt tubes I would treat it as a 1,200 to 1,500 watt PEP input rig which it will do without driving in into the grid current region.  The amp will run cooler and is much cleaner and the signal strength difference is almost unnoticeable.

I drive my Tbolt with a Pacemaker and the combination is pretty clean but it doesn't run quite at the old 2KW legal limit with the available drive from the Pacemaker.

Rodger WQ9E