[R-390] Variacs and solas: additional thoughts.

[ToddRoberts2001 at aol.com]

One thing that hasn't been mentioned in this thread about variacs is - can 
using a variac possibly extend the life of the 3TF7 ballast tube? I notice in 
many cases when first turning on an R-390A that the ballast tube will glow much 
more brightly for a few seconds due to the current surge of the cold 
low-resistance BFO and PTO tube filaments in series with the ballast. If one were to 
bring up the line voltage slowly using a variac, then this might cushion the 
initial voltage/current surge into the venerable 3TF7. After all, no thread 
beating a dead horse is complete without mentioning the 3TF7 ballast tube!