[Amps] TL922 Power Plugs

[Paul Christensen]

> To reiterate: The danger comes when neutral and ground are bonded together 
> at
> the appliance AND both neutral and ground wires back to the service 
> entrance
> become open. Under that circumstance, at least some of the "hot" AC will 
> appear
> on the chassis of the appliance.

For that to occur with both the neutral and ground opening, the grounded 
equipment chassis needs to find an alternate neutral path through other 
connections (e.g., grounded PL-259, RCA jacks, BNC, a grounded operator, 
etc.).  This probably presents the most serious potential fault condition if 
both ground and neutral become open.

However, it doesn't necessarily take the opening of both the neutral and 
ground to present a dangerous condition.  A danger still exists even when 
neutral and ground are bonded at the equipment and there is no wire-open 
fault of any kind because an equal portion of neutral current can divide at 
the equipment chassis (say 50% neutral conductor; 50% ground conductor if 
they're sized evenly) and result in two separate current paths back to the 
service entrance panel.  In this case, the danger is in the flow of current 
through the ground wire -- when it shouldn't.

Witness the many older Alpha and Henry amps in service in North America 
where 3-wire service is incorrectly used and although the ground lead is 
correctly tied to the amplifier chassis, that same chassis is tied to the 
neutral lead for the 120 VAC blower.  For these older amps fed with 3-wire 
service, ground and neutral become one.  Of course, equipment with an 
exposed chassis where the neutral and ground are tied would present a much 
more dangerous condition if located outside near water or perhaps a damp 
basement.

Another serious condition can still occur without both neutral and ground 
opening if: (1) the neutral and ground are tied at the equipment; and (2) 
only the neutral opens between the equipment and service entrance panel 
while ground remains intact.  In that case, neutral current divides and 
flows through the equipment chassis, the ground conductor, grounded PL-259s, 
BNCs, and a grounded operator.

Paul, W9AC