[NJARC] Hallicrafters SX-16 PS

[John Ruccolo]

Scott,

**NOW** you tell us that the tube was glowing
purple!!!

Your're right -- it's dead, Jim (Kirk, not Whartenby).
Toss it and get a new 5Z3.

Now, I know what you're gonna say -- "Aw, Gee, John, I
don't have another 5Z3." In a pinch, do this: Pull one
of the 6V6 output tubes to limit the plate current --
or pull BOTH if you're willing to use headphones --
and use an 80 tube temporarily. I'm sure Dr. D'Amico
can fix you up with a nice 5Z3.

Oh, wait, pulling both 6V6's may kill the headphones
too. I gotta RTFS. Just pull one for now.

JR


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

> Visit our web site - See http://www.njarc.org
> _______________________________________________
> Thanks Jim-
> Would a rectifier just "go gassy"? When I was
> testing the radio
> the night before, the tube had a purple glow to it
> on both sides.
> I was not sure if this was normal, and had been
> planning to ask,
> but last night the purple glow had the addition of
> lightning,
> which was quite disconcerting... Or deconcerting,
> had I had a
> concert on the radio... (Ow!)
> 
> I will check the voltages to ground: and am still
> checking
> continuity through the turns  of the transformer,
> but it appears
> the 110 primary has continuity(once the power switch
> is on), the
> heater secondary has continuity, and need to review
> both sides of
> the turns for the 5Z3 tube.
> 
> Scott
> 
> --- Jim Whartenby <antqradio at sbcglobal.net> wrote:
> 
> > Visit our web site - See http://www.njarc.org
> > _______________________________________________
> > 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
> 
> 
> 
>      
>
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