[R-390] Tube Substitutes

[James A. (Andy) Moorer]

You can't make that substitution.
The 6BH6 is a SHARP cutoff pentode. At about -4.5 volts on the control grid, 
it stops conducting entirely.
The 6BJ6 is a REMOTE  cutoff (or semi-remote cutoff according to some 
manuals). It doesn't stop conducting until at least -20 volts.

Substituting one for the other will screw up the AGC behavior of the 
receiver.

Curiously enough, you could possibly replace the 6BJ6 tubes with the 6BA6. 
The pinouts differ in that the cathode and suppressor grids are exchanged. 
All uses of the 6BJ6 have the cathode and the supressor grid connected 
together except for V509, so 6BA6 could be substituted everywhere except in 
V509. I've never tried this. The cutoff of the 6BA6 is "more remote" than 
that of the 6BJ6, so there will be some difference in behavior. Who knows if 
it would be significant?

James A. (Andy) Moorer
www.jamminpower.com

----- Original Message ----- 

> Excuse my greenhorn questions, but has anyone tried using 6BH6 tubes in 
> the 390 in place of the 6BJ6?  With what results?
>