[NJARC] Grounding question-Latest!

John Ruccolo jr6v6gt at yahoo.com
Mon Feb 16 01:31:24 EST 2009 

Hi Scott,

The 991 should continue to glow -- the glow should not disappear -- that's a clue that something is still not quite right -- could perhaps be the 991 itself. It only glows on one side because DC is applied -- would glow on both sides if AC was applied.

JR


--- On Mon, 2/16/09, Scott Roberts <ng19delta at yahoo.com> wrote:

> From: Scott Roberts <ng19delta at yahoo.com>
> Subject: Re: [NJARC] Grounding question-Latest!
> To: "New Jersey Antique Radio Club" <njarc at mailman.qth.net>
> Date: Monday, February 16, 2009, 1:07 AM
> Visit our web site - See http://www.njarc.org
> _______________________________________________
> 
> Ok- The hum is about 95% removed. The High Voltage negative
> to audio fixed most of it, the pi filter on the power supply
> fixed more.
> 
> I do have what sounds like brush noise form the dynamotor,
> so I will pull it for a look inside, as well as I am
> planning to re-repack the bearings: I had repacked them with
> synthetic grease, as recommended on one site, but I was not
> very happy with the stuff, so I am planning to repack with
> the original type grease, and go from there.
> 
> The radio is also doing something new- It is actually
> PICKING UP SIGNALS! However, only on one band so far. I am
> going to start checking through the alignment of the set. I
> imagine the ham who hacked it started fiddling with the
> adjustments trying to tune out the hum, which he put into
> the set!
> 
> Should it be a problem with the tuner sections, I do have a
> spare set for a BC-348-J which I will check to see if I can
> put into a 348-P.
> 
> I am quite happy with the fact it does seem to work.
> 
> A question for those who might know- The little neon
> tube(991?) used in the voltage regulator for the oscillator-
> What should it look like when operating? When the set is
> first turned on, it gets a large orange glow on one side of
> the little "hat" inside, which, as the set warms,
> shrinks and disappears altogether. Does this sound right, or
> should it have some other sort of glow?
> 
> Thanks!
> Scott
> 
> --- On Sun, 2/15/09, Scott Roberts
> <ng19delta at yahoo.com> wrote:
> 
> > From: Scott Roberts <ng19delta at yahoo.com>
> > Subject: Re: [NJARC] Grounding question- Good Lead!
> > To: "New Jersey Antique Radio Club"
> <njarc at mailman.qth.net>
> > Date: Sunday, February 15, 2009, 3:26 PM
> > Visit our web site - See http://www.njarc.org
> > _______________________________________________
> > Got into looking over the radio again this afternoon.
> > Re-examined the big transformer at the back of the
> set,
> > which houses 101A, 101B, 101C, and found something
> > interesting...
> > 
> > One of the regular mods done to the BC-348 model is
> that
> > the output connection is switched from High Impedance
> > output(early war) to Low Impedance output(later war).
> I had
> > noticed a wire removed from what is usually the high,
> and
> > one on the low. Only the low was marked, and I really
> > didn't think about it, as it looked like others
> I've
> > seen. Well, I took a closer look, and reread the
> schematic
> > on the transformer itself, and realized a major
> difference
> > from the schematic- instead of being paired in the
> normal
> > way- three levels, from top to bottom, of two
> terminals
> > each, and numbered 1 & 2, 3 & 4, 5 & 6, it
> is
> > actually setup this way- 1 & 6, 2 & 3, 4 &
> 5.
> > 
> > This caught my attention- ESPECIALLY when I noticed
> #6,
> > which is hidden at the lowest right side connection,
> has
> > "High" marked right above it- where you have
> to
> > look hard to see it.
> > 
> > So- Both High and Low impedance are connected- and No.
> 1 is
> > not. And guess what is supposed to connect to No. 1-
> The
> > High Voltage Negative output from the dynamotor.(and I
> > retraced this circuit to confirm it is that) Go
> Figure-
> > whoever hacked this radio never noticed the output
> > transformer had a non-standard layout, at least not as
> > regards many models, and did not bother to look at the
> > label: he just followed the general direction to move
> the
> > top left wire on it to the top right- which is correct
> on
> > many of these radios, but apparently not all... The
> high
> > impedance was cross-feeding with the high voltage
> negative,
> > with nothing going through the 101B circuit... Wonder
> if
> > that could be the overwhelming hum...
> > 
> > I'm going to go swap the yellow Hi-V neg wire back
> to
> > its proper position, and see what I get. 
> > 
> > Here's hoping- I'll post results.
> > 
> > Scott
> > 
> > --- On Sun, 2/15/09, Scott Roberts
> > <ng19delta at yahoo.com> wrote:
> > 
> > > From: Scott Roberts <ng19delta at yahoo.com>
> > > Subject: Re: [NJARC] Grounding question- Result
> > > To: "New Jersey Antique Radio Club"
> > <njarc at mailman.qth.net>
> > > Date: Sunday, February 15, 2009, 3:54 AM
> > > Visit our web site - See http://www.njarc.org
> > > _______________________________________________
> > > No Change.
> > > 
> > > Grumble.
> > > 
> > > Scott
> > > 
> > > 
> > > --- On Sun, 2/15/09, Scott Roberts
> > > <ng19delta at yahoo.com> wrote:
> > > 
> > > > From: Scott Roberts
> <ng19delta at yahoo.com>
> > > > Subject: [NJARC] Grounding question
> > > > To: "NJARC Radio Club"
> > > <njarc at mailman.qth.net>
> > > > Date: Sunday, February 15, 2009, 1:59 AM
> > > > Visit our web site - See
> http://www.njarc.org
> > > >
> _______________________________________________
> > > > This may sound like a simple question, but I
> do
> > need
> > > an
> > > > answer, although I am pretty sure I know it
> > already...
> > > > 
> > > > I am working on my BC-348-P, which I got at
> the
> > > swapmeet
> > > > back in August or September at Info Age.
> > > > 
> > > > I had thought I had corrected all the
> > modifications
> > > made to
> > > > the set, and returned it to original shape.
> > However, I
> > > still
> > > > get a loud hum over any and all settings. I
> have
> > been
> > > > starting to check voltages and resistances
> at the
> > > tubes with
> > > > the I-56-A test set.
> > > > 
> > > > Anyway, I just found a change I missed- The
> dial
> > lamp
> > > > circuit has been heavily modified- The power
> in
> > lead
> > > has
> > > > been moved from the AVC-Off-MVC switch,
> front
> > wafer,
> > > > position 1, and moved to the  VT-86(217,
> First
> > I.F.)
> > > tube
> > > > socket terminal 7. Continuing through the
> > circuit, the
> > > > original series arrangement of the lamps has
> been
> > > changed to
> > > > parallel, and resistor 503(the flat 60 ohm
> dial
> > lamp
> > > > resistor) has been bridged across with a
> piece of
> > bus
> > > wire.
> > > > 
> > > > Could these changes, having been left
> unnoticed
> > &
> > > > intact, be the cause of the overriding hum?
> I am
> > about
> > > to
> > > > restore the circuit, as I would anyway, but
> > wanted to
> > > see
> > > > what you guys think.
> > > > 
> > > > I'll let you all know the
> results(hopefully
> > > positive
> > > > & hum free) after i complete it and test
> the
> > unit
> > > again.
> > > > 
> > > > I am still not sure the neon tube in the
> > oscillator
> > > plate
> > > > voltage regulator, (id 218, 2J991, or 2V991,
> > JAN-991)
> > > is
> > > > operating properly, and wonder if it could
> be
> > related
> > > to
> > > > either, or both issues- the convoluted lamp
> > wiring, or
> > > the
> > > > hum...
> > > > 
> > > > Thanks!
> > > > Scott
> > > >
> > >
> >
> ______________________________________________________________
> > > > NJARC mailing list
> > > > Home:
> > http://mailman.qth.net/mailman/listinfo/njarc
> > > > Help: http://mailman.qth.net/mmfaq.htm
> > > > Post: mailto:NJARC at mailman.qth.net
> > > > 
> > > > This list hosted by: http://www.qsl.net
> > > > Please help support this email list:
> > > > http://www.qsl.net/donate.html
> > >
> >
> ______________________________________________________________
> > > NJARC mailing list
> > > Home:
> http://mailman.qth.net/mailman/listinfo/njarc
> > > Help: http://mailman.qth.net/mmfaq.htm
> > > Post: mailto:NJARC at mailman.qth.net
> > > 
> > > This list hosted by: http://www.qsl.net
> > > Please help support this email list:
> > > http://www.qsl.net/donate.html
> >
> ______________________________________________________________
> > NJARC mailing list
> > Home: http://mailman.qth.net/mailman/listinfo/njarc
> > Help: http://mailman.qth.net/mmfaq.htm
> > Post: mailto:NJARC at mailman.qth.net
> > 
> > This list hosted by: http://www.qsl.net
> > Please help support this email list:
> > http://www.qsl.net/donate.html
> ______________________________________________________________
> NJARC mailing list
> Home: http://mailman.qth.net/mailman/listinfo/njarc
> Help: http://mailman.qth.net/mmfaq.htm
> Post: mailto:NJARC at mailman.qth.net
> 
> This list hosted by: http://www.qsl.net
> Please help support this email list:
> http://www.qsl.net/donate.html

More information about the NJARC mailing list