[Johnson] Warning about high ac line voltage.

[Sherrill Watkins]

Gentlemen: I happened to be reading the book entitled "Care and Feeding of
Power Grid Tubes" published by Eimac in 1968 and noticed something
interesting. Eimac states that for power grid tubes an increase in the
filament voltage of just 3 percent over the rated filament voltage can reduce
the tube life by as much as 50 percent!! (Please don't argue with me about
this. I suggest to obtain a copy of the book and read it.) My measured ac
line voltage is about 5 percent over the U.S. Standard of 120 vac.
Therefore,it may be reasonable to presume that any vacuum tube equipment
operated on a line volatage of 125 vac will have a filament voltage that is 5
percent higher than the rated filament voltage. -73- Sherrill W. k4own