Preston Electronics, LLC


Stayin' Alive

Have you ever set up at a club and received a shock when you touched your equipment? If so, you have been the victim of faulty electrical wiring. You are lucky to be reading this.

The 'standard' AC outlet has very specific standards for correct wiring. Unfortunately, non-technical people often think they can repair or replace a broken outlet. Worst case is when someone puts in a three-wire grounded outlet in an old building with only two wires, and gets the wiring backward. The results can be lethal.

If you look closely at a standard AC outlet, you will see a short slot, a long slot, and a round slot. The short slot is the 'Hot' slot where high voltage is present. The long slot is the 'Neutral' slot, which is the return path for electric current. The round slot is a 'Safety Ground' terminal. The metal chassis and cabinets of your equipment are connected to the wire that plugs into this ground terminal. If the equipment malfunctions and causes AC voltage to be connected to the chassis, it will be grounded by this wire and protect you from electrocution. For safety, each outlet must be correctly wired and your AC cords must have all three blades.


Outlet tester

We recommend that you carry with you an outlet tester such as the one shown. This model can be purchased at Radio Shack, but similar ones are available at any hardware store for less than $10. Use it to test every outlet that you plug into, to be sure it is correctly wired and has a ground. If the outlet tester indicates that there is a problem with the outlet, you are risking electrocution if you use the outlet.

If the tester shows reversed hot and neutral, the outlet is EXTREMELY DANGEROUS. You would be justified in declining the gig if you can't find any correctly wired outlets. Call it to the attention of the owner. If he won't do anything about it, report it to the fire department.

You may also find an outlet with only two slots (old style ungrounded outlet). PLEASE DO NOT CUT OFF THE GROUND PIN of your cords to use this outlet. Suggest to the owner that he get an electrician to upgrade the electrical wiring - at least for the stage circuits.

Plan ahead for this situation. Here's your shopping list:

Alligator clipBattery clipGrounding adapter

1. Alligator or crocodile clips (RadioShack Cat # 270-346 or Cat # 270-356)

2. Battery clip (RadioShack Catalog #: 270-344)

3. 'Grounding adapter' from (Radio Shack or your local hardware store)

4. 20-50 ft of #18 stranded insulated wire (RadioShack Cat # 278-1226 or 278-1220)


Attach the alligator clip to one end of the wire and the battery clip to the other to make one long clip lead.

Notice that there is a tab (or possibly a wire) on the adapter that makes contact with the outlet cover plate screw. If you are lucky, that screw is connected to grounded conduit. Plug the outlet tester into the ground adapter, then plug that into the two slot outlet. If the adapter has a wire instead of a tab, touch the wire terminal to the cover plate screw. If the tester shows normal, loosen the screw and connect the wire or the tab to it.

If the tester shows no ground, try to find a COLD water pipe and attach the battery clamp to it. (Be sure it's not a gas pipe!) Then connect the alligator clip to the ground tab or ground wire of the grounding adapter. Plug the tester through the adapter into the outlet and be sure the tester indicates good wiring.


One other thing.... look at the grounding adapter blades. You will notice that one blade is wider than the other. For awhile, two-slot outlets were made with a short slot and a long slot and were said to be Polarized. Unfortunately, before that time they were made with two narrow slots, and there was no standard for which slot was hot or neutral. The grounding adapter will not fit that type of outlet, and it is best not to try to make it do so.

Live long and prosper!