[R-390] Ballast Tube Thread

[Barry Hauser]

Ah-hah!  A classical mid-20th century example of CYA engineering philosophy.

Hmmm.. better stock up on some more ballast tubes so my A will be properly
C'ed.

Uh-oh .. from the notes of the intrepid Three-Star General Torment:  "Letsee
now, the factor of tube aging -- of the 6BA6's -- was unknown, so you guys
worked with Amperite to come up with a new custom ballast -- with even less
aging history -- and threw that into the mix?  I see."

Which shows to go you -- even when you think you have your A's well C'ed
....

Not to mention that we need to keep this thread going 'til it goes bang -- 
it being the 4th and all.  BTW -- anybody have some burnt out ballasts to
blow up tonight -- assuming they're loaded with hydrogen, not helium.

Barry

PS -- As I write this the History Channel is playing "The Crossing" with
Jeff Daniels as G. Washington.  Am I mistaken, or didn't he play opposite
Jim Carey in "Dumb and Dumber"?  Either (a) I don't know how I feel about
that, being rather fond of the original George and/or (b) Jeff D. has quite
a range and may qualify as the worlds most underrated actor -- tho' I
wouldn't mind trading paychecks.



----- Original Message ----- 
From: "JamesMiller" <jmiller1706 at cfl.rr.com>
To: <r-390 at mailman.qth.net>
Sent: Sunday, July 04, 2004 11:11 AM
Subject: Re: [R-390] Ballast Tube Thread


> >From page 15 section 4.2.2.1 AC Power Units of Final Engineering Report
on
> Radio Receivers R-389 and R-390 Sept. 15, 1953:
>
> http://www.r-390a.net/faq-eng-r3.pdf
>
> "The filament regulation circuit for the oscillator filaments should also
be
> covered here although this ballast tube is mounted on the IF unit.
> Considerable work was done with Amperite Corp. in designing this special
> ballast tube which feeds a constant 300 mils to the two 6 volt 300 mil
> oscillator tubes used in the VFO and BFO. These three tubes are connected
in
> series across the 26 volt filament supply. The ballast tube (3TF7)
operates
> on a current of 290 to 330 mils and holds this current within ±10 mils for
> input voltage variations of ±15%. This reduced the 15% variation to
> approximately 3%. There is some question if a filament regulator is
> necessary in these receivers since the oscillators are very good even
> without regulation. However, since the stability was a big factor in this
> design and since the factor of tube aging was not known, the regulator was
> included."
>
>
>
>
>
> _______________________________________________
> R-390 mailing list
> R-390 at mailman.qth.net
> http://mailman.qth.net/mailman/listinfo/r-390
>