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

[jackiv at juno.com]

HI AGAIN.          I am not well versed on this rx. I had 2 but did not
go deep into them. One I did refurb as well as possible by replacing the
paper caps, cleaning the turret and some other minor things.
        Many owners have tried to mod these things with product detectors
and avc mods. Most from typical QST and 73 articles.
As used, the ssb was derived from the outboard adapter fed from the if
out connector.
                As to the 6C4 replacement, I would not favor it as the
output from the 6C4 can be much higher than the tv oscillator tube. 
 A 6DZ4 may be quiter, not sure.
  As always with these BAs,  have fun.       jack
 ===================================================================

> I also noticed that the osc. tube in the unit modified with the DC
> filament supply is a 6DZ4 instead of the 6C4 per the manual.  The 
> 6DZ4
> seems to be designed more for UHF, but again I can't see a 
> compelling
> reason for the change.  Any ideas?  
> 
> Thanks for the help!
> 
> Rich AA7P
> 
> 
> 
> -----Original Message-----
> From: jackiv at juno.com [mailto:jackiv at juno.com]
>  Tuesday, May 28, 2002 6:22 AM
> To: r.hebel at verizon.net
> Cc: hallicrafters at mailman.qth.net
> Subject: Re: [Hallicrafters] R-274D/FRR - Concerning a circuit mod
> 
> 
> 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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