[Collins] Grounding attachments S-1 line

David Knepper cra at floodcity.net
Mon May 24 17:34:13 EDT 2004


  Jerry, I think that the bottom middle screw would make a great tie point
rather drilling a hole.

  I have seen some sets done this way.

  Dave, W3ST
  Secretary to the Collins Radio Association
  Publisher of the Collins Journal
  www.collinsra.com
  ----- Original Message -----
  From: "Dr. Gerald N. Johnson, electrical engineer" <geraldj at isunet.net>
  To: "Cal Shermerhorn VE4XQ" <banjo at mts.net>
  Cc: <collins at mailman.qth.net>
  Sent: Monday, May 24, 2004 2:42 PM
  Subject: Re: [Collins] Grounding attachments S-1 line


  > Sure enough, my 32S-1 has no grounding screw while my 75S3B has a
  > grounding screw on the back panel. As I looked I saw all those RCA phono
  > jacks sticking out, several not used. Any of them would be a good ground
  > with a piece of braid soldered to the shell of a good Switchcraft RCA
  > phono plug. Better than drilling a hole into a part or cable harness
  > inside the back of the chassis.
  >
  > As for logic, in the beginning of the S-line grounding wasn't yet the
  > hot topic it became in the 60s. I recall from the book about Collins ham
  > gear that the prototype 75S1 had a two wire line cord like all other ham
  > gear of that era. In the early 60s grounding became more important for
  > prevention of user shocks, and in some hamshacks, surely to minimize RF
  > burns on the operator's fingers and lips. Then three wire line cords and
  > ground posts or screws began to appear on all brands of radios.
  >
  > Sometime after I left Collins in 1966, Art was tickled by an ungrounded
  > appliance and he decreed that the power switch on every piece of
  > equipment shall have an insulating cover. At that point Art had lost his
  > confidence in grounds. By that time OSHA and UL had quite a bit of
  > confidence in grounds and tended to require them on everything that
  > wasn't double insulated. Today OSHA only believes on grounds when
  > there's a special ground maintenance program in the workplace. Otherwise
  > OSHA prefers GFCI which are often tripped by the line bypass filters in
  > vintage radios (large enough capacitors to draw 10 ma or more from the
  > line to the chassis, and that's enough current to tickle the tender
  > finger when the user and chassis grounds aren't connected by something
  > other than the finger).
  >
  > Another good ground screw location would be one of the chassis hold down
  > screws on the bottom of the case, but not one through a rubber foot.
  >
  > 73, Jerry, K0CQ, Technical Advisor to the CRA
  > --
  > Entire content copyright Dr. Gerald N. Johnson, electrical engineer.
  > Reproduction by permission only.
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