[NJARC] BC-348

[John Ruccolo]

Hi Scott,

In general terms, you want to start by injecting an RF signal at the antenna and move forward, or start by injecting an audio signal at the output stage and move back.

But first, check is any of you operating voltages are anywhere *near* correct.

Regards,

John


--- On Tue, 11/4/08, John Ruccolo <jr6v6gt at yahoo.com> wrote:

> From: John Ruccolo <jr6v6gt at yahoo.com>
> Subject: Re: [NJARC] BC-348
> To: "NJARC Radio Club" <njarc at mailman.qth.net>, ng19delta at yahoo.com
> Date: Tuesday, November 4, 2008, 1:27 PM
> Visit our web site - See http://www.njarc.org
> _______________________________________________
> Scott,
> 
> Sorry about the B-24. But, seriously....
> 
> So you ARE running the 348 off the dynamotor, correct? I
> assume the dynamotor "spins up" as it should? Did
> you measure the B+ output from it?
> 
> How loud is the hum? You said you hear it regardless of vol
> control setting....hmmm. What happens if you stick an audio
> signal on the grid of the output stage? Or measure the plate
> voltage at the output stage, for starters.
> 
> Did you try "jamming" a signal into the antenna
> via an RF generator? Is so, what happened? If not, try that
> too.
> 
> JR
> 
> 
> --- On Tue, 11/4/08, Scott Roberts
> <ng19delta at yahoo.com> wrote:
> 
> > From: Scott Roberts <ng19delta at yahoo.com>
> > Subject: Re: [NJARC] BC-348
> > To: "NJARC Radio Club"
> <njarc at mailman.qth.net>
> > Date: Tuesday, November 4, 2008, 2:17 AM
> > Visit our web site - See http://www.njarc.org
> > _______________________________________________
> > Well, I haven't had any replies yet...
> > 
> > I added a pair of filter caps and a choke to thw 28VDC
> > power supply I cobbled together, but no change in the
> hum.
> > So, I am going to replace the caps in the dynamotor
> and see
> > what that does. After that, ? I guess I just start
> fiddlin
> > with stuff.
> > 
> > Any help still appreciated!
> > Thanks!
> > Scott
> > 
> > 
> > --- On Mon, 11/3/08, Scott Roberts
> > <ng19delta at yahoo.com> wrote:
> > 
> > > From: Scott Roberts <ng19delta at yahoo.com>
> > > Subject: [NJARC] BC-348
> > > To: "NJARC Radio Club"
> > <njarc at mailman.qth.net>
> > > Date: Monday, November 3, 2008, 2:24 PM
> > > Visit our web site - See http://www.njarc.org
> > > _______________________________________________
> > > Hi Everybody-
> > > I am messing about with my BC-348P(Not my
> Uncle's,
> > but
> > > the one I picked up at the swap meet a few months
> > back) and
> > > am setting it up for its original power supply.
> Dave
> > Sica
> > > did me a great favor, and swapped me a BC-348
> > dynamotor and
> > > mount in exchange for a radio I had he was
> interested
> > in. I
> > > cleaned & relubricated the bearings on the
> > dynamotor,
> > > and put it into the de-modified chassis after
> testing.
> > My
> > > test rig is simply a 25.2 VAC transformer,
> rectified
> > through
> > > 4 1N4007 diodes, but no filter caps. (This tuning
> > units, see
> > > nothing may be important...)
> > > 
> > > The dynamotor tested out nicely- on 25.2
> > VDC(rectified) it
> > > was putting out around 230 VDC. The few caps in
> the
> > > dynamotor are original, one a nice metal one, the
> > other a
> > > paper cap. (It is a DM-28-Q, from a BC-348-Q)
> Caps
> > have not
> > > been replaced in the dynamotor, but all caps were
> > redone in
> > > the BC-348-P.
> > > 
> > > When I switch the unit on, in either AVC or MVC
> mode,
> > with
> > > the proper impedence headset, or speaker, I get a
> hum,
> > but
> > > no indication of volume control- no scratchiness,
> > nothing,
> > > but a hum. I have tried running it through the
> FL-30-M
> > > filter(similar to FL-8-A) but it has no effect.
> Could
> > this
> > > be a hum from my cheap-a** power unit(literally
> thrown
> > > together to form a circuit) that could be solved
> by a
> > couple
> > > filter caps before it comes into the radio?(If
> so,
> > would
> > > 47/450Es be about right?)
> > > 
> > > I have been rechecking my wiring repairs, and,
> other
> > than
> > > tearing out the tuning units and looking into
> them I
> > see
> > > nothing obviously missed. Tubes have all been
> tested
> > on my
> > > Precision tester, and check out fine.
> > > 
> > > Ideas?
> > > 
> > > Thanks!
> > > Scott
> > > 
> > > _______________________________________________
> > > NJARC mailing list
> > > NJARC at mailman.qth.net
> > > http://mailman.qth.net/mailman/listinfo/njarc
> > _______________________________________________
> > NJARC mailing list
> > NJARC at mailman.qth.net
> > http://mailman.qth.net/mailman/listinfo/njarc
> 
> 
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