[Boatanchors] SX-122 hum and noise

[The Pollacks]

Don't know about this particular unit, but I have traced many cases of hum
to poor grounds at tuning caps, tube sockets, and terminal strips.

-----Original Message-----
From: boatanchors-bounces at mailman.qth.net
[mailto:boatanchors-bounces at mailman.qth.net] On Behalf Of Byron Tatum
Sent: Thursday, March 25, 2010 7:45 PM
To: Boatanchors at mailman.qth.net
Subject: [Boatanchors] SX-122 hum and noise

Hello-
    I am trying to root out two types of objectionale noise coming out of
audio channel on mySX-122. The receiver has a  new filter cap, that I have
ruled out, as there is no ripple on the B+. I recently installed shielded
leads on the AC power run from rear panel to front panel on/off switch. It
did not seem to help.
        1. A constant hum is present in the audio, it is not too terribly
objectionable but quite a bit more than any of my other tube receivers.
        2. A lower pitched hum is added in when the BFO is turned on, and
this hum is noticably louder. The hum does not change in any way as the BFO
is tuned.
    I believe hum in the audio has been a common problem with these sets,
does anyone have any advice or info?
                                                        Thanks, Byron.  
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