QSC CX4T User Manual download pdf (Page 10)

CX6, CX6T, CX12 and CX12T

When the amplifier is first turned on, the red “PROTECT” LED on each channel will light for about two or

three seconds, during which the output relays will stay open to mute the speakers. After the turn-on muting

interval, the “PROTECT” LEDs turn off, the green “POWER” LEDs light, and the output relays close to enable

the speaker outputs. Even during the muting interval, the yellow “SIGNAL” and red “CLIP” LEDs operate

normally if there is a signal present. If the “CLIP” LED is on while the amplifier is muted, cut the gain back

immediately to avoid a full-power blast of sound when the output relays close. If a channel stays muted

with “PROTECT” lit, or if its “SIGNAL” or “CLIP” indicators light up when the gain is turned all the way down,

it may be defective; see the troubleshooting segment for more information.

The “SIGNAL” LED indicates signal levels that are -30 dB (referenced to full rated output power) or higher.

Whe the amplifier is shut off, the amplifier should mute both channels virtually instantaneously, with the

“PROTECT” indicators lit until the power supplies are discharged.

TROUBLESHOOTING

Problem: Channel will not come out of muting

• If reducing the gain control to × attenuation does not release muting, the channel is defective or

overheated (see “Overheating,” below).

• If reducing the gain releases the muting, raise the gain back up slowly while you watch the “SIGNAL”

and “CLIP” indicators; the problem may be an abnormal signal (with excessive ultrasonic energy, for

example) that could otherwise damage your speakers.

PROBLEM: No sound (CX6/CX12)

• Is the channel muted? (If the “PROTECT” indicator is lit, the channel is muted; see below.)

• Is the “SIGNAL” LED lit or flashing? (If so, the speaker is open or blown, there is an open circuit in the

speaker wiring, or there is an open circuit in the internal output wiring of the amplifier.)

• If the “SIGNAL” indicator is dark, there is probably not enough signal, or even none at all. Try turning

up the rear panel attenuators or boosting the signal level at the input.

• If the “SIGNAL” indicator shows little or no activity but the “CLIP” LED is lit or flashing, there is probably

a short circuit in the speaker wiring, especially if the “PROTECT” indicator starts flashing. It is also

possible, but less likely, that the channel’s output relay is defective and will not open, thereby short-

circuiting the channel output and producing the same symptoms.

PROBLEM: Channel goes into muting, with “PROTECT” LED on (CX6/CX12)

• If the fan is running full speed, the channel probably suffers from severe overheating. Unless there

is a blockage in the flow of cooling air, the channel should return to normal within a minute or so (see

“Overheating,” below).

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QSC CX4T User Manual Page 10