[R-390] Audio HUM WAS: B+ short in RF deck

[Dennis Wade]

Barry, yes...it has both fuses on the B+ line..

          D.


On Fri, Jan 2, 2015 at 1:25 PM, Barry <n4buq at knology.net> wrote:

> Does this receiver have the fuse in the B+ line?  If not, can you measure
> the load on the B+ supply to ensure it's not more than the rated load?
>
> Regards,
> Barry - N4BUQ
>
> ----- Original Message -----
> > From: "Dennis Wade" <sacramento.cyclist at gmail.com>
> > To: "R-390 HF Receiver List" <r-390 at mailman.qth.net>
> > Sent: Friday, January 2, 2015 3:13:05 PM
> > Subject: Re: [R-390] Audio HUM WAS: B+ short in RF deck
> >
> > Happy New Year all,
> >
> >         An update to the audio him issue.  Received replacement caps for
> > C603 and 606 and replaced the 20 year old caps on the headers I made back
> > when I got the receiver.  Audio hum remains at previous levels.
> >
> >         Placing a 47 mf cap across the B+ reduces the hum drastically, as
> > before, and another 47 mf cap in parallel drops the him down to about 160
> > mv on a 195 volt B+ line.
> >
> >         Obviously, something isn't working right.  I did check the dc
> > resistance of the inductors which is within spec.  Nothing obviously over
> > heating.  I am very tempted to wire in the additional C.
> >
> >         Short of swapping in another inductor(s), anything else I can
> > check?  The rectifiers are good.
> >
> >                       Dennis
> >
> > On Sat, Dec 13, 2014 at 8:46 PM, Roy Morgan <k1lky68 at gmail.com> wrote:
> >
> > >
> > > On Dec 13, 2014, at 11:37 PM, Dennis Wade <
> sacramento.cyclist at gmail.com>
> > > wrote:
> > > >
> > > > I did find a 10 uf @ 450 (after, of course), and hung that across,
> > > dramatic reduction in hum.
> > > >
> > > > Looks like I'll be ordering some caps…
> > >
> > > BINGO  I think you’ve got it.
> > >
> > > Check hayseed hamfest for plug-in caps that will do the job.
> > >
> > > Roy
> > >
> > > Roy Morgan
> > > RoyMorgan at alum.mit.edu
> > > K1LKY Since 1958
> > >
> > >
> >
> >
> > --
> > "If they trust you, it is an extraordinary privilege, and you simply
> can't
> > abuse it."
> >       - A. Alan Post  1914-2011.  California Legislative Analyst
> 1949-1977.
> >
> > -------------------------
> > Dennis L. Wade
> > KG6ZI
> > Carmichael, CA
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-- 
"If they trust you, it is an extraordinary privilege, and you simply can't
abuse it."
      - A. Alan Post  1914-2011.  California Legislative Analyst 1949-1977.

-------------------------
Dennis L. Wade
KG6ZI
Carmichael, CA