Remove the trans,take it to a electric motor rewind shop and have it vacuum
impregnated....No baloney with shims,etc,etc,...End of story...Jim K7RDX..
----- Original Message -----
From: "EP Swynar" <gswynar@durham.net>
To: "W5CUL" <w5cul@sbcglobal.net>; "'Van K7VS'" <wa7fab@cdsnet.net>
Cc: <amps@contesting.com>
Sent: Sunday, June 10, 2007 10:45 AM
Subject: Re: [Amps] HV transformer buzzing!! Help Please
> In the past, I've actually "injected" silicone into the innards of
> bell-ended transformers, in anticipation of (possible) vibration from
older
> such units...
>
> I don't know if this notion really works, or not --- they were, after all
&
> in all instances, pre-emptive moves on my part --- but, I can honestly
(and
> happily!) say that whenever I've done this, I've never once had a
> "...vibrator" in the bunch.
>
> Perhaps a better idea might be to tip the transformer upside down, & then
> simply pour something a little more viscous --- like maybe
varnish? ---down
> in between the end bells & the windings themselves...let it soak in a tad,
> then pour in some more...
>
> Last but not least, the thing should be allowed to thoroughly dry --- a
> process that'd no doubt take several days to complete.
>
> As I say, I've never personally tried this last trick myself, but in the
> final analysis, aren't transformer windings sealed with some sort of a
> shellac, anyway? And if the original stuff dries hard over time, & becomes
> brittle (resulting in vibration), what harm could a "fresh" application of
> varnish / shellac like this be...?
>
> ~73~ Eddy VE3CUI - VE3XZ
>
> **************************
>
>
> ----- Original Message -----
> From: "W5CUL" <w5cul@sbcglobal.net>
> To: "'Van K7VS'" <wa7fab@cdsnet.net>
> Cc: <amps@contesting.com>
> Sent: Sunday, June 10, 2007 1:19 PM
> Subject: Re: [Amps] HV transformer buzzing!! Help Please
>
>
> > Van,
> >
> > Transformers will vibrate when voltage is supplied, specifically the
> > windings. This can happen if the primary and secondary windings are not
> > wound tightly. Or if the winding as a whole does not completely fill
the
> > window of the iron, and thus is a little loose, you can develop some
> > buzzing. I would check the HV transformer for shims (wooden wedges)
> between
> > the windings and the iron core. If there are no shims, I would make
some
> > out of wood and place them between the winding and the iron core such
that
> > the windings are tight within the assembly. If there are shims already
in
> > place, then readjust them until the noise is abated. Now all of this
> advice
> > is without actually seeing the transformer, but from what you describe,
it
> > certainly has the symptoms of loose windings. Hope this helps. I will
> > defer to Tom and others if this does not solve your problem.
> >
> > 73,
> >
> > Mike
> > W5CUL
> > -----Original Message-----
> > From: amps-bounces@contesting.com [mailto:amps-bounces@contesting.com]
On
> > Behalf Of Van K7VS
> > Sent: Sunday, June 10, 2007 1:14 AM
> > To: amps@contesting.com
> > Subject: [Amps] HV transformer buzzing!! Help Please
> >
> > I just finished tearing down and rebuilding a HV/LV supply for a Globe
> King
> > 500A. Galvanized the chassis and repainted all the xfmrs. Looks great,
> > works great BUT the supply is buzzing quite loudly. I know it is coming
> > from the HV supply on this deck. LV supply quiet. The buzz is there
when
> I
> > turn on the HV supply switch and become quite a bit louder when I load
the
> > HV supply down (loading and running the transmitter section).
> >
> > Any thoughts of what might cause this noise. I don't think its any kind
> of
> > arcing but a mechanical noise and probably around 60 cycles...maybe. It
> is
> > low pitched. This supply using a filament xfmr for the 866A retifiers,
a
> > 350 ma choke and large High voltage transformer. I know I have to
isolate
> > the noise to one of the xfmrs but then what do I do? Any help/thoughts
> > would be appreciated.
> >
> > Thanks much. Van, K7VS
> >
> > PS. Next step is to clean off the modulator deck, remove all the rust
and
> > rebuild it. The RF is pretty clean but doing the same to it. I fired
up
> > the transmitter section today and got 300+ watts into a dummy load thru
> bird
> > wattmeter. Pretty good for an old boy that probably hasn't been on the
> air
> > for thirty or forty years with a very rusty modulation section and very
> > rusty power supply deck that now looks like it just came out of the
> factory!
> > HI HI.
> >
> > _______________________________________________
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> > Amps@contesting.com
> > http://lists.contesting.com/mailman/listinfo/amps
> >
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>
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