[AMRadio] R-390A Help

[Larry Szendrei]

Another way of dealing with missing or bad 26Z5s is to rewire the 
sockets for 12BW4s, connecting the heaters in series. IIRC this was 
published long ago in Electric Radio, along with the suggestion of using 
a PL34 (an inexpensive tube at the time) to replace the 3TF7 regulator. 
The latter also required a slight re-wire of the socket, again IIRC. I 
did both mods when I acquired  an R390-A about 13 or so years ago and 
never looked back.

73,
-Larry/NE1S