[R-390] R-390A Current Regulator Tube replacement?

[Dan Rae]

One alternative I don't remember seeing for losing the hard to find 
ballast tube is to run the two oscillator tube filaments from the 
otherwise unused 12.6 Volt center tap on the power transformer. 

This involves adding one wire in the power supply (from transformer pin 
9, the centre tap,  to the previously unused pin 9 on the connector 
J111), moving the filament feed to the IF strip from the present pin 1 
inside plug P111 to pin 9 (in mine, it's the thinner of the two white / 
brown wires), and finally shorting out the current regulator pins 2 and 
7 in the IF strip.   And that's it. 

This has some advantages over the methods using a resistor, it's cheap, 
retains the original tubes rather than replacing them with 12BA6s, but 
does not have the advantages of another form of current regulator, solid 
state, for example.  

Anybody tried this before, or got any comments for or against?  
73
Dan
ac6ao / g3ncr