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

Dennis Wade sacramento.cyclist at gmail.com
Fri Jan 2 16:14:18 EST 2015


That should be drops the ripple on the B+ down to 160 mv.

       D.

On Fri, Jan 2, 2015 at 1:13 PM, Dennis Wade <sacramento.cyclist at gmail.com>
wrote:

> 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
>



-- 
"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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