Diagnose Power Line Problems With A Simple DeviceJuly 24, 2008 4:17 pm Live Sound
One of the first things I check when we start to set up for a Rusty Strings show in an unfamiliar venue is, “Where’s the AC power source?” We’ve had everything from a multi-tap outlet right at the sound man’s position and another one onstage to a single two-prong outlet “around back of that other building there” for everything to plug into - that was at an outdoor gig. I always take a long extension cord, just in case.
Naturally, our gear all uses 3-wire, grounded AC cables, as do our power strips, cube taps, etc. Most venues, like restaurants or clubs, have grounded AC wiring in place, as required by modern electrical codes. But sometimes we find ourselves playing at someone’s old house or homestead that still has the old style ungrounded 2-wire AC outlets.
I take 3-to-2 AC adapters with me to handle such a case, but plugging in to an ungrounded system is always a bit iffy because of the possibility of introducing hum into the system, not to mention the risk of “ground shocklets” from microphones, guitar strings, etc.
The fact is, even if there is a nice-looking grounded outlet for you to use, there is no way to tell by looking at it whether the ground connection, or any of the wires for that matter, are hooked up right. Well (singing heroically) here it comes to save the day: the portable AC line tester!
Testing 1, 2, 3
OK, a line tester can’t actually save the day, but it can at least tell you that the day needs saving! Here’s a life-size photo of the cute little unit I take to our gigs:
It’s pretty simple to use, not to mention cheap (like under $10). You just plug it into the outlet you want to test and observe the various lights on the unit. Specific patterns of lights correspond to specific wiring problems that the unit has detected. Only one pattern is deemed “Correct.” (That big red circle is a button you press to control the test process.)
Besides “Correct,” the light patterns indicated on the side of the unit are labeled as follows:
- Open Ground
- Open Neutral
- Open Hot
- Hot/Grd Reverse
- Hot/Neu Reverse
Detailed explanations of these conditions and others as well as how to remedy them are provided in the instruction booklet that comes with the unit.
Of course, you usually can’t remedy the conditions - you don’t own the place! But, if you turn up a dicey reading at one outlet, you can at least ask if you can try another outlet, perhaps in a different room around the corner or something. Show the manager the readout on the device if there are any questions.
As a bonus, if you use the bad outlet anyway and the PA hums or acts funny or unpleasant string shocks occur, you will have something specific to blame. Maybe you can sue!Tags: equipment -->