[Collins] Grounding attachments S-1 line

[Dr. Gerald N. Johnson, electrical engineer]

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.