Troubleshooting – QSC Audio TD-000271-01 User Manual

Page 10

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TROUBLESHOOTING

10

EN

NO POWER, NO LIGHTS, NO FAN

Confirm that the AC cord is fully seated and connected to a

live outlet. Check the AC source by trying another device

such as a lamp. Check the BREAKER on the back of the

amplifier by pushing in the button. If the breaker trips off

quickly, the amplifier needs servicing.

AMPLIFIER LOSES VOLUME

If the amplifier is worked too hard, GuardRail™ will

reduce volume to prevent thermal muting. The fan should be

running at full speed. Reduce input signal somewhat and the

amp should return to normal gain within 1-2 minutes. If the

amp feels hot and the fan is not running, it needs to be

serviced.

CHANNEL 1 PRODUCES DEEP BASS ONLY.

Check the position of the CROSSOVER switch on the rear

panel. Set on FULL RANGE for normal, independent use of

each channel.

CHANNEL  INPUT SEEMS DEAD.

Check the position of the CROSSOVER switch on the rear

panel. Set on FULL RANGE for normal, independent use of

each channel.

AMPLIFIER SOUNDS DISTORTED.

If the red CLIP LED is flashing, the amplifier is being played

beyond its normal rated power. GuardRail™ circuitry will reduce

volume somewhat to prevent severe overdrive, but if the input

signal is further increased, the limiter can be overridden, with

increased distortion.

If the speakers or speaker cables are shorted or defective,

the amplifier may distort at lower-than-normal levels, with

increased flashing of the red CLIP LED. This should be

checked by trying an alternate speaker and cable.

If too many speakers are connected to each channel

(impedance below 4 ohms), the amp will overload more

easily and will probably run hot.

If the sound is distorted or garbled without flashing the red

CLIP LED, the distortion is not occurring inside the amplifier.

Either the speaker is bad or the input signal is distorted.

• Confirm that the speaker is OK by trying a different unit.

• Input overload can occur if the amplifier Gain controls are set too

low, and the input source is overdriven to compensate Reduce the

source volume until the distortion clears up, and increase amp Gain

to reach the desired level. It is generally desireable to keep the

amp gains at or near their full, clockwise, position.

• Check all input connections. Do not plug two different sources into

the same channel. Use a mixer to blend sources.

NO SOUND, WITH BLUE LED ONLY, NO GREEN OR

RED LED

Confirm that the Gain controls are turned up. Confirm that

the input cables are correctly installed at both ends. If using

1/4-inch speaker cables, do not confuse with input cables.

Confirm that the source is active. If necessary, try another

source, or connect another amplifier to the existing source.

NO SOUND, BUT THE GREEN LED IS RESPONDING

The green LED indicates the amp is producing a signal, so

sound should be heard if the speaker is connected. Check

the speaker connections at both ends, and try a different

speaker.

NO SOUND, RED LED ON

The amp mutes briefly when turned on and off to prevent

thumps. If the amp overheats severely, it will mute until it cools off.

The fan will be running at full speed, and sound should

resume in less than a minute. If the amp feels hot and the fan

is not running, it needs to be serviced.

BACKGROUND HUM

Balanced XLR or TRS cables are better for long runs. Hum can be a

problem when connecting to TV-cable rigs, since the TV cable often

creates a ground conflict. Request or install a TV-cable isolator to

reduce this problem.

Hum can also occur earlier in the signal chain, depending on the

types of connections. It often helps to plug everything into the same

AC strip, if the total power consumption is not excessive.

As a last resort, mild hum can sometimes be reduced by

lowering the amp gain, and increasing the source gain to

compensate, but you must ensure that the source can deliver

the extra volume without overload distortion. If this does not

reduce hum, it is coming from the source.

AMPLIFIER NEEDS SERVICING

The following conditions indicate possible unsafe conditions

that require service before using. If observed, unplug the AC

cord from the wall and when safe, remove the amp for

servicing.

• If the amplifier emits smoke or burning smells

• If the case is severely dented or deformed

• If the amplifier is soaked with any fluid

• If internal parts sound loose

• If the AC breaker trips when power is applied

• If the amplifier is dropped, carefully inspect for damage or

loose parts before attempting to use.

TROUBLESHOOTING

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