[Jukebox-list] Jukebox Wiring Question - switched and fused neutral

[Jimmy Day]

In the good old days (like in the early 1900s), there was "knob and tube" 
wiring, which had no ground. Just 2 separate wires run throughout the house. 
Plugs were not polarized, they had no need to be. The plugs on old jukeboxes 
are like this, 2 prongs of the same size. When electrical systems began 
using a ground, the "Greenfield" conduit was used, this is a flexible metal 
similar to the "gooseneck" on your table lamp. It was connected to the 
receptacle box, and the early adapters had a metal tab that was "supposed" 
to be, but rarely was, connected under the screw that held the receptacle 
cover. Now we had a dedicated neutral, and one blade of the plug was wider 
(neutral is wider).

As per the National Electrical Code - The ground wire (green or bare) must 
not carry any current, and must have an unbroken path to the electrical box. 
The neutral (white) does carry current, but must not be switched or fused. 
It has no appreciable voltage to ground. All neutrals and grounds are 
connected together at the main electrical box, and nowhere else. On a long 
run, in commercial/industrial systems, it is common to actually measure a 
volt or so between neutral and ground, due to inductive pickup.

The hot wire (black in 120 volt systems) is the only conductor that may be 
switched or fused.

As for the GFI receptacle, I have not seen any with only two wires. The ones 
in hair dryers are actually part of the unit and are not designed to power 
anything else. AFAIK, two-wire GFIs are not available for new construction, 
and if one feels that a GFI does not need to be grounded should see what 
their local electrical inspector thinks ;-) Using one inside a jukebox is of 
questionable benefit. What we are concerned about is leakage to the metal 
parts; for example, an old cracked fluorescent socket or the brittle wiring 
in an old AMI possibly touching the metal chassis. A regular 3-wire GFI 
would sense current in the ground circuit and immediately trip. A 2-wire one 
may not, since it is not "looking" at the ground circuit.

The GFI receptacles one finds at the supply houses do have a ground 
connection. I have also installed GFI breakers in the main electrical box. 
These breakers, unlike regular breakers, MUST be grounded to work. "Ground 
Fault Interrupter" - it trips if it detects ANY current difference between 
any of the three wires.

This is why we are getting our newbies confused. One says to use a 
three-wire cord, another says no, that is not safe unless it is done a 
certain way, someone else says yes it is safe but it must be connected so 
and so, etc, etc. I would be confused too!

*jimmy jukebox