[R-390] Regulated filament voltage

[rbethman]

Drew,

I see the 3TF7 and the other mentioned methods as adequate.  It is that 
simple.

With over ten years of running an R-390A running 24/7, I have have had 
"other" things go pfft!  Like a 6AK5, that took out a resistor in the 
the audio deck.

I've yet to have a ballast tube go pfft!  I also acquired a number of 
them that are kept as spares, BEFORE they hit a ridiculous price.

I get more concerned with the ones out there that STILL have the 
selenium rectifier in use.  That would be a very wise change, since the 
gases emitted when THEY croak are very unhealthy.  The same can be said 
for the AC line input filters, since the GFCI issue is hitting more and 
more of us.

The addition of an external bucking transformer comes to mind as a wise 
thing with the power companies pushing line voltages up into the near 
130VAC range to keep from replacing all that wire to carry the load.

I have NO objection to tinkering!  I just like to do so in the areas 
that really are issues.

YMMV, and each to his own.

Bob - N0DGN

On 2/20/2011 1:31 PM, Drew P. wrote:
> We tinker with these radios because we like to tinker.  Atop that, we, as stewards of these fine receivers, in a way envision ourselves to be somehow allied with the brilliant designers who created them.  We then become "armchair engineers". We conduct seances to commune with the ghost of Art Collins on the Astral Plane.  No harm in that.  We see the Achilles Heel (every design, even the best, has at least one) as the somewhat failure prone 3TF7, and this coupled with the high price of a 3TF7, and ready availability of technology that wasn't around when these were designed, makes BallaSubstitutes ir-"resist"-ible.
>
> How many mods do you see for the RF deck?  Not many.  We can't find a way to REALLY improve upon it.  But a BallasTube that goes "pop", $50 or more for a new one, cheap new electronics, a cheapskate mentality, mostly easy design at 60 Hz and no RF to deal with, and idle time making the hands wanto do the Devil's work....you get the picture.
>
> "That LM-317?  I swear, Art made me do it!!"
>
> Drew