[R-390] R390: 60 Hz on Audio

[Jim M.]

Some questions:  Is the shield cover installed over the filters?  I have
seen the top mounting screw come loose causing some erratic behavior.  Have
also had the cover short against one of the filter lugs causing weird things
(but I don't recall getting hum).  

-----Original Message-----
From: r-390-bounces at mailman.qth.net [mailto:r-390-bounces at mailman.qth.net]
On Behalf Of Larry Snyder
Sent: Tuesday, June 09, 2009 7:16 PM
To: r-390 at mailman.qth.net
Subject: Re: [R-390] R390: 60 Hz on Audio

Well, the mechanical elements are driven and sensed magnetically.
Just a data point.
-ls-


Jon Schlegel <ews265 at rochester.rr.com> wrote:
> Thanks Roger,
> 
> I'm beginning to question the grounding arrangement that I used when 
> I reinstalled the filters into the chassis after measuring them.  I 
> will also look closely at the grounding accomplished by S502/503 rear.
> 
> ADDITIONAL INFO:  I removed V501 and injected 455 kHz to pin 5 
> (plate) of the V501 socket and still see 60 Hz on recovered audio as 
> previously described.  This does suggest the 60 Hz is getting in 
> through the filter/switching/grounding arrangement as you 
> suggest.  Exactly how the mechanical filters would be sensitive to 60 
> Hz is still a mystery.

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