[NJARC] Philco 42-321

[Jim Whartenby]

Edward
This Philco, like John Ruccolo said, is not designed as a "hot chassis"
set. As long as the capacitor in "item 8" is not leaking.  If it is
leaking, then, unfortunately, it becomes a hot chassis AC/DC radio.

My comments were about the coil in "item 8".  It is so small in value
as to not be all that effective unless something else is going on in
the circuit.  Most sets just use a large value capacitor with a voltage
rating of 600 or so volts to AC ground the B- supply lead.

I think it is just a circuit trick thought up by the designer to
cheaply improve the AC grounding of the B- supply.  This is much like
the long leaded capacitor used as an IF filter.  I think it was a
0.047uF cap with long leads that formed a series LC circuit roughly
tuned to 455kc.  It helped (inexpensively) keep 455kc out of other
circuits in the radio.

That radio I mentioned with the two FM bands used an electrodynamic
speaker.  With new and smaller filter caps placed in a better location,
the hum bucker circuit in the speaker actually was adding hum to the
audio.  So I removed it.

The customer mentioned, after listening to the set, that tube radios
sounded so much better then transistor radios.  I think so too!
Regards,
Jim

--- Edward Otte <edotte at optonline.net> wrote:

> Visit our web site - See http://www.njarc.org
> _______________________________________________
> 
> 
> Jim,
> 
> I am not sure I fully understand. I just started taken note of the
> schematic
> and it dawned on me. Depending on how I hook the AC plug into the
> socket the
> chassis will either be ground/ neutral 0 volts or 120 Volts hot!
> Yikes! So
> the -B supply goes there too. 
> 
> But I agree with you how many Henry's could there be in a wire
> twisted six
> or seven times around a 1/2 inch capacitor. 
> 
> Edward
> 
> Edward
> This is an AC/DC set and it predates polarized plugs.  So it looks
> like
> it is a series LC circuit used to connect the B- power supply
> terminal
> to the chassis.
> 
> It would be nice to know the inductance so we could calculate the
> resonant frequency.  Need to know how many turns of wire and what is
> the cross section of the capacitor? And then there is the matter of
> Q.
> 
> I don't think Philco used this circuit for long.  I don't remember
> seeing this in a late 40s AC/DC set I reworked that had AM and both
> the
> old and new FM bands.  My gut feeling is that this inductor is not at
> all critical and can be deleted when you replace the old wax coated
> ones with modern capacitors.
> Regards,
> Jim
> 
> --- Edward Otte <edotte at optonline.net> wrote:
> 
> > Visit our web site - See http://www.njarc.org
> > _______________________________________________
> > 
> > Hello all,
> > 
> > I have a general question about the Philco 42-321. There is a
> > "condenser &
> > choke assembly" which consists of a 0.2 uF capacitor with a number
> of
> > wires
> > wrapped around it. There is a Philco part number but what if I
> wanted
> > to
> > replace it? The coil portion is just a wire and it has a certain
> > radius
> > would I have to recreate this or is there an easy solution? Thanks
> in
> > advance.
> > 
> > Edward
> > 
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> 
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