[NJARC] RCA Victor C-2E

[Jim Whartenby]

There is much more to this then just simple time constants.

The bigger the capacitor used in the filter circuit, the larger the
peak capacitor charging current.  Exceeding the peak rectifier current
is why vacuum tube rectifiers generally have lower emission when
compared to other tubes in the radio. 

The reason for this is that the high capacitor charging current exacts
a price on the rectifier cathode and the service life of the rectifier.

Check out "Radiotron Designer's Handbook" (RDH), 4th Edition, pages
1170 through 1176.  Also check out pages 99 and 100 of RDH to calculate
the value of the resistors, one for each plate, that are needed to
reduce the peak rectifier current to a safe value.

If you don't want to do the reading and the math, simply use a
convenient resistor value between 100 to 150 ohms at 3 watts for a
typical radio receiver.  If your rectifier has an octal base, the
resistors can be connected to the unused socket pins.  Move the
transformer plate leads to an unused rectifier socket pin and then
connect the resistor from this new point to where the wire was
originally.  Repeat this process for the other transformer / rectifier
plate wire.


Once the resistors are installed, it will not matter how big (within
reason!) the replacement filter capacitor is.  No more of "I can't find
an 8uF 450 volt capacitor!  Use a 20uF (or larger) if that is what is
on hand.

Your radio will thank you with longer trouble free service!
Regards,
Jim

PS
I noticed a few cars with NJ plates at Dayton, OH.  Who did I miss
meeting?

--- Harry Klancer <klancer2 at comcast.net> wrote:

> Visit our web site - See http://www.njarc.org
> _______________________________________________
> Edward,
> 
> Consider. Time constant of an RC is   T = RC   (dropoff is
> exponential).
> (Remember, microfarads are 10 -6, kilohms are 10 +3)
> 
> A bigger C just means that the voltage from the peak doesn't drop off
> as fast.. For 60 cycle half wave, there are 16 milliseconds between
> peaks.
> Make yourself a little drawing, and you'll see what I mean.
> 
> As long as C is not so large that the RC never discharges, the dc 
> voltage will
> be OK, so you can use a larger C. 60 percent larger is not normally a
> 
> problem.
> As Marty says, 47/47 instead of 50/30 is fine. BTW, modern standard 
> values are
> 22 and 33 and 47, etc.
> 
>                                                           Harry K
> 
>                                          
> 
> 
> 
> Edward Otte wrote:
> 
> > Visit our web site - See http://www.njarc.org
> > _______________________________________________
> > What is the rule of thumb here on going bigger?
> >
> > -----Original Message-----
> > From: njarc-bounces at mailman.qth.net
> [mailto:njarc-bounces at mailman.qth.net]
> > On Behalf Of Marty Friedman
> > Sent: Tuesday, May 15, 2007 2:07 PM
> > To: New Jersey Antique Radio Club
> > Subject: Re: [NJARC] RCA Victor C-2E
> >
> > Visit our web site - See http://www.njarc.org
> > _______________________________________________
> > good work Aaron I missed it in the Sams index.. I found it in
> Beitmans. The 
> > C2 had 50/30 mfd, in the C3 they "improved" it to 50/50 mfd. so 2-
> 47s will 
> > be fine.
> > Marty
> >  
> >
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> >
> >   
> 
> 
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