[R-390] R-390A power transformer hum

[Barry Scott]

I seem to recall that from my R-390A/URRs.  The transformer in the
R-390/URR doesn't seem to do that.  The cost reduction must have taken
its toll there.

Thanks,
Barry - N4BUQ

On Sat, Oct 19, 2024 at 8:21 AM Tom Frobase <tfrobase at gmail.com> wrote:
>
> Some are noisier than others.  I have a large supply here if you want to
> replace it.  Contact me offline ... tom, N3LLL
>
> On Sat, Oct 19, 2024 at 8:18 AM Leo Reynolds via R-390 <
> r-390 at mailman.qth.net> wrote:
>
> > Is it normal for a R-390A power transformer to hum audibly? Not through
> > the speaker, though there is a little there too, but through slight chassis
> > vibration. It is there from the instant of turning on power and changes
> > slightly as the rectifier starts conducting and B+ flows. It is easily
> > audible in the shack, as if it were a small AM broadcast transmitter minus
> > the blower.
> >
> > Thanks,
> >
> > Leo Reynolds
> > K4LDR
> >
> >
> >
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