[R-390] Which Ballasubstitution? You decide.

[Drew Papanek]

Hello All,

On the subject of ballasubstitutions a question was raised by Kenneth.

He inquired as to which of two methods is the better. Each has advantages 
and disadvantages:

1. 12BH7 modification: same heat production as 3TF7, needs another tube, 
keeps the stock 6BA6's,
     looks reasonably authentic.   12BH7, 12BY7, 12BV7  can be used and can 
have gas, shorts,
     and/or no emission so long as the heater is good.  Using a defective 
tube as a power resistor
     gives you a sense of accomplishment; that you got something for 
nothing.

2. Two 12BA6 and a paperclip: about 3.8 watts less heat on the IF deck, 
needs other tubes, big empty
    socket.  12BA6 are easy to find.  I did not use the traditional 
paperclip to jumper the ballasocket;
    instead I  wrapped a fine wire around the two correct pins on the 
defunct 3TF7 and plugged it back
    into the socket.  Except for missing the very faint glow of the 3TF7 now 
gone dark, looks original.

Make your choice (Remember also many other substitution schemes).

Drew