[Hallicrafters] R-274D/FRR - Concerning a circuit mod

[jackiv at juno.com]

Rich, that is a Sarkes-Tarzian plug in solid state replacement for the
5U4G and other rectifiers with the same socket connections. piv is not
high enough for the 5R4GY tho.
The ballast tube is a current regulator for the osc. and mixer.  This is
the Hallicrafters version??  (SX-73)

73   jack    jackiv at juno.com

On Mon, 27 May 2002 18:43:07 -0400 "Rich Hebel" <r.hebel at verizon.net>
writes:
> I am restoring a R-274D/FRR.
> 
>  
> 
> I am trying to reconcile the actual unit to the schematics.  There 
> are
> clearly a couple of non-factory mods.
> 
>  
> 
> One of them has me a little puzzled.  
> 
>  
> 
> According to the manual, filament power to the VFO and 1st Mixer is 
> fed
> from the main power transformer through a ballast tube and then on 
> to
> the filaments.  
> 
>  
> 
> In the unit I have, someone has replaced the ballast tube 
> arrangement
> with a bridge rectifier and a pi filter.  I guess I can understand 
> why
> someone might put a DC supply to the filaments.  However, in series
> between the output of this supply and the filaments is a device I 
> need
> some help with.  It is a black metal can, about 1" diameter by 1.5"
> tall, with an octal pin base.  The only markings on it are "JD" and
> "S-5251" and a small graphic that looks kind of like the schematic
> symbol for a diode with a symbol for a fuse overlapping it.  Does
> anybody have any idea what this is?  It is a two terminal device, 
> with
> pins 1 and 7 connected.  No other manufacturers ID or markings are
> present.
> 
>  
> 
> Any help would be appreciated.
> 
>  
> 
> Tnx
> 
>  
> 
> Rich AA7P 
> 
> 
> 
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