[ARC5] [Milsurplus] BC-348 PSU questions

[WA5CAB at cs.com]

As I wrote yesterday, the BC-348-JNQ versions have a slightly different B- 
derived bias circuit from all of the BC-224's and all the rest of the BC-348 
models.  The JNQ alone has 25 ohms (two 50 ohm in parallel) resistance 
connected between the B- choke and chassis.  Bias to the 6K6GT is taken off of 
the top (connection to the dynamotor B-) of the choke and bias to the 6SA7GT 
mixer is taken across the 25 ohm resistor pair.  In all other receivers, the 
only bias is for the VT-152 audio output tube.

And again, I don't know what the DC resistance of the choke in the JNQ 
audio pack is but in the others it is the quoted 300 ohms.  I think I have a 
somewhat hacked Q.  If it still has the audio pack, I'll measure the choke 
resistance unless someone else does so sooner.

Robert Downs - Houston
wa5cab dot com (Web Store)
MVPA 9480

In a message dated 09/30/2015 08:52:58 AM Central Daylight Time, 
ianmwilson73 at gmail.com writes: 
> For the record, the DC resistance of the audio choke is about 300 ohms. 
> The
> developed negative bias is used only for the audio o/p tube grid, as far 
> as
> I
> can see on the schematic.
> 
> 73, ian K3IMW
> 
> 
> On Tue, Sep 29, 2015 at 6:24 PM, Roy Morgan <k1lky68 at gmail.com> wrote:
> 
> >
> >On Sep 29, 2015, at 8:50 PM, Ian Wilson <ianmwilson73 at gmail.com> wrote:
> >
> >>>
> >>>NOTE WELL: For an AC supply in this receiver, the negative side of the
> >>>supply must be left floating.  It goes to ground through a bias filter
> >>>network which is part of the audio output transformer (I hope yours
> >still
> >>>has the original transformer...?).
>