Ac Safety Tips; Power Source Integrity; Turn-On Sequencing - Yamaha PM4000 Operating Manual

way to ground via the safety ground,
instead of via a person's body. When
checking AC power lines at the outlet, be
sure you have proper testing tools and
some familiarity with the danger of shock
hazards from AC power. Follow the dia-
gram shown here, being careful not to
touch metal with your hands. Do not short
the test leads together. If you are not
familiar with AC power distribution, don't
experiment; have a licensed electrician
perform these tests and correct any dis-
crepancies.
Figure 4-4. Testing A 3-wire AC Outlet

4.2.6 AC Safety Tips

1. If you are going to verify the quality of AC wiring,
there are two inexpensive items you should carry.
One of these is a commercial outlet tester, the other
is a neon lamp type AC voltage tester. These items
are inexpensive and available at most hardware
stores, electrical supply houses and some lighting
stores. It is advisable to also have an RMS (or
averaging) voltmeter to measure the exact AC line
voltage.
2. The outlet tester should be used on all power
outlets, The neon voltage tester should be used to
check for voltage differences between microphone
and guitar amps, microphones and electric key-
board chassis, and so forth.
3. If you're not sure whether an outlet is good, don't
use it. Just in case, carry a long, heavy duty
extension cord. A good extension should be made of
#12-3 (12 gauge, 3 wires), and no longer than 15
meters (about 50 feet).
4. If there is no suitable power source at a venue, don't
plug in your equipment. Any fault in the wiring of
the AC outlet is potentially hazardous. Rather than
take a chance with damage to equipment and
possibly lethal shock, it is best to refuse to use a
faulty outlet until it has been repaired by a licensed
electrician. Don't take unnecessary risks.

4.2.7 Power Source Integrity

Finally, make every effort to assure that your source
of power is clean and reliable. Synthesizers, computer
sequencers and other digital equipment, in particular,
normally require a filtered power source with surge
protection in order to avoid glitches, system hangups
and possible component damage. Power distribution
strips with such protection built in are widely available
commercially. The ultimate protection is provided by
using a power line isolation transformer, such as the
"Ultra Isolation" transformers sold by Topaz. Such
devices are designed not only to exclude noise and
distortion in the AC signal, but also to hold the voltage
at the device's output to a nearly constant value regard-
less of major fluctuations of the line voltage at its input.

4.2.8 Turn-On Sequencing

In larger systems, it is often difficult to obtain a
sufficient number of 20-amp circuits to accommodate
the power surges that may occur when the equipment is
turned on. Many modern power amplifiers, for example,
each require the full capacity of a 20-amp circuit at
turn-on, though their operating current requirement is
usually much lower. The solution to this problem is to
use a stepped turn-on sequence; in fixed installations,
the turn-on sequence is sometimes automated with
timing and control circuitry.
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