[R-390] R-390A Alternative to 6DC6 RF amp

[Larry H]

I wanted to give you a little more info about the list of candidate tubes that I started with.  The list was restricted to those tubes with only the '7CM' basing diagram because the suppressor grid (pin 7) is now grounded or should be.  This is due to production modification 2.  If it were tied to the cathode (pin 2) as in the original design, which is  reflected in the schematics in TM11-856A and TM11-5820-358-35 (dated 12-8-1961), then 2 more basing diagram tubes could be used.  These 2 very commonly used tech refs do not include the RF amp changes made in production mod 2.  The only schematics I've seen online that include it are the ones created by Pete Wokoun and are included in all the Y2K tech refs.  Thanks Pete.
Regards, Larry