[NJARC] Hallicrafters SX-16 PS

Wed Mar 19 01:43:25 EST 2008

Scott
I wouldn't go through all of the trouble of disconnecting the
transformer secondaries at this time.  The problem could be just a
gassy rectifier.

If you pull all of the tubes and apply power, the transformer will be
unloaded.  Let the set run for a half hour or more with the transformer
unloaded while checking the transformer's temperature.

If it is just barely warm to the touch then the transformer is most
likely OK.  If the filament winding reads between 6 and 7 VAC then you
know the transformer is working properly.  Expect higher then normal
voltages since the copper losses are nil.  You are not pulling any
power out of the transformer when it is unloaded.  The only power used
is that which is required to set up the magnetic field and supply the
back EMF to the primary.

If you hear a slight buzz or notice that "burnt smell" AND the
transformer gets noticeably warmer then the rest of the chassis, then
there may be reason for concern.  A shorted turn will pull power from
the primary which will directly heat up the transformer.

Some transformer problems are from leakage to ground instead of a
shorted turn.  You can check each side of the high voltage secondary to
ground for the same voltage.  The voltage readings should be very
close.  The low voltage windings are a bit harder to test for leakage
since it is common practice in some sets to try to reduce the filament
induced hum.  It might be necessary to disconnect the low voltage
windings in order to check for leakage there.

Lastly, poorly designed and mounted transformers may actually induce
current into the chassis which in effect becomes a shorted turn.  The
cure is to space the transformer a bit above the chassis to reduce this
coupling.  So if the transformer gets warm but is otherwise OK, spacing
could be the issue.
Regards,
Jim

--- Scott Roberts <ng19delta at yahoo.com> wrote:

> Visit our web site - See http://www.njarc.org
> _______________________________________________
> I am going to take a heavy look at the transformer- I have some
> suspicions about it: the wax on the bottom, which is dripped out
> of it, is heavier since I last looked at it: it is also on top of
> connections I just made when recapping. Also, I want to check
> continuity through the windings: I tested the mains coil(110AC
> in) and it is NOT indicating continuity! It is showing an open-
> even though current is coming out the other side. Seems like
> there is something wrong. So I am going to disconnect all the
> connections, and test continuity of all the windings, and see
> what I come up with. I understand from postings elsewhere on the
> net that these transformers have a tendency to met out and short,
> so I am concerned this may be the issue...
> 
> Scott
> 
> 
> --- Scott Roberts <ng19delta at yahoo.com> wrote:
> 
> > Visit our web site - See http://www.njarc.org
> > _______________________________________________
> > The adapter is a straight through type, with the outside tabs,
> > and I'd used it last week with no issues. I will take a look
> > and
> > see- maybe something got inside it, but I doubt it. The blown
> > out
> > piece of the tube is on the pin which goes to the number 2
> > terminal on the transformer. Looks like blue wire: I am still
> > trying to find a chart of the transformer wiring and outputs-
> > all
> > I find is the same one which is on the Hallicrafters schematic:
> > which has no values on it... I am checking for a short: when I
> > have the DMM set for continuity(beep) I get an alternating ow
> > volume beep between the tube contact on the socket, and the
> > chassis. (A solid chassis to chassis connection gets a solid
> > tone
> > beep)
> > 
> > Anyone got a diagram of the transformer for an SX-16?
> > 
> > Scott
> > 
> > --- John Ruccolo <jr6v6gt at yahoo.com> wrote:
> > 
> > > Visit our web site - See http://www.njarc.org
> > > _______________________________________________
> > > Scott,
> > > 
> > > I figured you replaced the caps -- but I had to do a
> > > sanity check, just in case. ;-)
> > > 
> > > Hey, what about this "adapter" you put on the BFO
> > > socket? Could that have shorted to something?
> > > 
> > > I don't think the tube failed on its own (although
> > > *anything* is possible). I think something external
> > > caused it to fail. By your description, it sounds like
> > > the B+ got shorted to ground.
> > > 
> > > JR
> > > 
> > > --- Scott Roberts <ng19delta at yahoo.com> wrote:
> > > 
> > > > Visit our web site - See http://www.njarc.org
> > > > _______________________________________________
> > > > ALL CAPS REPLACED!!!!
> > > > 
> > > > The only change I made from last night was I rotated
> > > > the chassis
> > > > on the bench 180 degrees so I could access the BFO,
> > > > and put in
> > > > the adapter between the BFO 6J7 tube and socket, so
> > > > I could test
> > > > the voltages...
> > > > 
> > > > I will make the checks you just mentioned tonight,
> > > > and post my
> > > > findings. (I'm hoping my findings include another
> > > > 5Z3 tube in my
> > > > spares pile...)
> > > > 
> > > > When I was working on testing last night, I had the
> > > > chassis
> > > > upside down while I found the problem: then I put it
> > > > right side
> > > > up and ran it- I wonder if something in the tube was
> > > > damaged, and
> > > > came loose after it cooled, and shorted it
> > > > internally? 
> > > > 
> > > > Scott
> > > > 
> > >
> > 
> > 
> >      
> >
>
____________________________________________________________________________________
> > Never miss a thing.  Make Yahoo your home page. 
> > http://www.yahoo.com/r/hs
> > _______________________________________________
> > NJARC mailing list
> > NJARC at mailman.qth.net
> > http://mailman.qth.net/mailman/listinfo/njarc
> > 
> 
> 
> 
>      
>
____________________________________________________________________________________
> Looking for last minute shopping deals?  
> Find them fast with Yahoo! Search. 
>
http://tools.search.yahoo.com/newsearch/category.php?category=shopping
> _______________________________________________
> NJARC mailing list
> NJARC at mailman.qth.net
> http://mailman.qth.net/mailman/listinfo/njarc
> 