[Hallicrafters] AC/DC Halli's, Grounds and HUM

[JM/CO]

Anyone who insists on using these AC-DC cheapo radios without an isolation
transformer obviously has a death wish. "MCM electronics", as well as "All
Electronics" now has 1.0 amp isolation transformers in stock for under $20.
These are small enough to be easily installed PERMANENTLY inside the case of
these radios.
Even though the present ( presumably knowledgeable ) owner may be aware of
the dangers of these sets, someone "down the line " may be killed. Do
yourself, and someone else a favor, and install one of these units.
Oh-yeah--it will eliminate that " hum when grounded" thing too.
Chuck N1LNH
-----Original Message-----
From: Phil Atchley <ko6bb at elite.net>
To: hallicrafters at mailman.qth.net <hallicrafters at mailman.qth.net>
Date: Tuesday, February 12, 2002 9:59 PM
Subject: [Hallicrafters] AC/DC Halli's, Grounds and HUM


>Hello All
>I have a Halli 5R10A (5 tube AC/DC set) that I recently completely recapped
>and went through with a fine tooth comb.  While I was doing the refurb I
>installed a new line cord with a  "polarized" (one prong fatter) line cord,
>making SURE that the neutral line (fat prong) is tied to the B minus side
of
>the power supply (as it should be).  The chassis then connects to this B-
>lead through a coupling capacitor for RF bypassing (AND AC line isolation).
>
>The set shows ONE big quirk though (and it did when it arrived here before
>the recap).  IF I tie the ground lug (connected to chassis) on the 3 screw
>antenna strip to the station ground I get a LOT of hum.  The set DOES NOT
>like to be grounded.  This precluded using my antenna/rig select switches
to
>apply an antenna to the set UNTIL I lifted the jumper from the ground screw
>to one of the antenna screws and operate the set in the "isolated" antenna
>mode (I.E. Doublet setup).  Doing this the hum does NOT show up and
>everything appears to be fine.
>
>Question 1:  Is this typical of the Hallicrafters AC/DC rigs of 5R10A, S-38
>vintage or should I be looking for a problem somewhere? (I don't remember
>this happening on my S-120 though back in the barracks in '63 I don't think
>I used a ground)
>
>Question 2:  Does anybody have the schematic and service notes for the
5R10A
>that they could scan and send me?  The set is so simple one can really do
>all the work without them (as I did) but it'd be nice to have.  (No, the
set
>isn't on the BAMA site).
>
>73 de Phil  KO6BB
>Loving home provided for wayward Boatanchor Receivers
>ko6bb at elite.net
>Merced, Central California
>37.18N 120.29W CM97sh
>
>
>
>
>
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