[R-390] 6tf4 Ballast

[Steve Hobensack]

Tom, a rule of thumb for ballast tube nomenclature: The first number usually 
means the current in milliamps the ballast tube will hold. The number at the 
end usually indicates the "head voltage" required for regulation. As in the 
6tf4 , it will hold 600 mills of current and you need at least 4 volts over 
and beyond the tube voltage for minimum holding of current. 4 volts is at 
the edge of hold , ideal voltage would be a few more volts above 4 volts 
more than tube filament voltage. This may be explained at the  amperite web 
page. I don't know the web address offhand.

73....Steve...n8ye