Lg Electronics MIC/LINE MIXERS Manual Do Utilizador

20

•

Are the 

SUB ASSIGN 

 switches set

correctly?

•

Are the 

MAIN MIX Fader 

 and 

SUB

Faders 

 turned up?

•

If it’s one of the 

MAIN OUTs 

, try

unplugging all the others. For example, if
it’s a TRS 

MAIN OUT, unplug the associ-

ated XLR  outputs. If the problem goes
away, it’s not the mixer.

•

If it’s a stereo pair, try switching them
around. For example, if a left output is
presumed dead, switch the left and right
cords, at the mixer end. If the left speaker
is still dead, it’s not the mixer.

•

Turn the channel Faders 

, 

EFX 1

RETURN 

 and 

EFX 2 SEND 

 down,

one by one. If the sound disappears, it’s
either that channel or whatever is plugged
into it, so unplug whatever that is. If the
noise disappears, it’s from your whatever.

•

Our favorite question: Is the 

POWER

switch on?

Details concerning Warranty Service are

spelled out page 23.

If you think your CFX Mixer has a problem,

please do everything you can to confirm it be-
fore calling for service. Doing so might save you
from the deprivation of your mixer and the as-
sociated suffering.

Of all Mackie products returned for service

(which is hardly any at all), roughly 50% are
coded “CND” — Could Not Duplicate, which
usually means the problem lay somewhere
other than the mixer. These may sound obvious
to you, but there’s some things you can check.
Read on.

•

Is the 

ASSIGN 

 switch set correctly?

•

Is the channel Fader 

 turned up?

•

On mono channels, try unplugging any
INSERT devices.

•

Try the same source signal in another
channel, set up exactly like the suspect
channel.

When setting up for a show, oftentimes you

are plugging into an AC power distribution sys-
tem you know nothing about. You may even be
faced with 2-wire outlets that are missing the
third safety ground pin. It’s a good idea to have
a three-wire AC outlet tester in your toolbox so
you can check the outlets yourself to make
sure they are wired correctly. These testers will
tell you if the polarity of the hot and neutral
wires is reversed and if the safety ground is dis-
connected. Don’t use an outlet if it is wired
improperly! This is to protect yourself as well
as your equipment.

If you find that you must plug into a two-

wire outlet, you will need to use a two-wire to
three-wire adapter (cheater plug). These come
with a metal tab that you put underneath the
center screw that holds the AC outlet faceplate
in place. This center screw 

must be grounded.

You can check it by connecting the adapter to
the outlet and then plugging in your handy-
dandy AC outlet tester.

NEVER bypass the AC
plug’s ground pin. This is
dangerous!

The majority of AC outlets encountered in

homes and clubs (in the U.S.) are served by a
240VAC center-tapped service entrance trans-
former. This provides two phases of AC power
on either side of the center tap, at 120V each.

If lighting is used in a show, it is preferable

to power the lights from one leg of the service,
and power the audio equipment from the other
leg. This will help minimize noise from the
lights coupling into the audio (particularly if
SCRs, or light-dimmer switches, are used).

In order to minimize ground loops, the safety

grounds for all the outlets should be connected
to a common (“star”) grounding point, and the
distance between the outlets and the common
grounding point should be as short as possible.