Roderick M. Fitz-Randolph w5hvv at AENEAS.NET
Wed Feb 18 12:57:05 EST 1998

>  Sean, be very careful ...the S38 series receivers all had AC-DC power
>supplies with no isolating transformer and one side of the power cord is
>always HOT to the 120vac line.  When the plug is inserted in one way, the hot
>sideof the power line  is connected directly to the metal chassis and the
>case, creating a definite shock, or even electrocution hazard if one happens
>to sumultaneously touch ground, or any grounded metal object. Most of those
>vintage tabletop radios have no polarity protection, and can be plugged in
>either way. Later 2 wire cords had a larger pin on the ground side of the
>power cord. There have been many cases of electrocution caused by this
>long-abandoned power supply system.
>73, Dick W0EX
A suggestion:  When restoring any of the older AC/DC sets, it might be
apropos to replace the original cord (many of them have rotted insulation,
anyway) with a modern 3-pronged plug.  Assure that the chassis is connected
to the ground lug and the "hot" prong (determined by using a voltmeter on
your wall plug, in reference to the ground lug) used to go to the "hot" side
of the filaments and rectifiers.  The remaining prong is not connected.
This should eliminate any safety hazard, I believe.  What say others?

This is, of course, assuming your house wiring and wall plugs are correctly
installed and that your wall plugs have a properly connected ground lug.

I've made several AC/DC transmitters using this scheme, in conjunction with
plastic chassis/cabinets along with 12 volt actuated reed relays for the CW
key and there is no exposed voltages other than the 12 volts available on
the key..... pretty damned safe!  Of course, I don't operate them on the edge
of my bathtube when I'm taking a bath!  Some sense in handling is required.
Millions of AC/DC sets were manufactured and sold and used safely.  Only a
few dumb bunnies set them on the side of the tube while taking a bath (like
I've seen my sister do!  Fortunately, it never fell in and she is still alive).

Rod, N5HV
w5hvv at aeneas.net

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