[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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