Legacy Car Audio LA-2078, LA-478 TroubleshootingTroubleshooting, Amplifier will not power up

Amplifier will not power up.

•Check for good ground connection.

•Check that remote DC terminal has at least +12v DC.

•Check that there is battery power on the + terminal.

•Check all fuses.

•Check that Protection LED is not lit. If it is lit, shut off amplifier briefly and then repower it.

STOP

High hiss or engine noise (alternator whine) in speakers.

•Disconnect all RCA inputs to the amplifier(s) – if hiss/noise disappears, then plug in the component driving the amplifier and unplug its inputs. If hiss/noise disappears, go on until the faulty/noisy component is found.

•It is best to set the amplifier's input level as insensitive as possible. The best subjective S/N ratio is obtainable this way. Try to drive as high a signal level from the head unit as possible.

Protection LED comes on when the amplifier is powered up.

4 ohm

2 -c hannel Amplifier (Operating in Stereo)

YES! 4 ohm

Two 4-ohm speakers, wired in stereo, will present a 4-ohm load to each channel of the amplifier. Most two- channel amplifiers will work well in this configuration.

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1600 63rd street. brooklyn. ny 11204

4 ohm

2 -c hannel Amplifier

(Operating in

Bridged Mono)

NO! 4 ohm

Two 4-ohm speakers, wired in parallel to a bridged two-channel amplifier. will present a 2-ohm mono load to the amplifier. MOST TWO-CHANNEL

AMPLIFIERS DO NOT SUPPORT 2-OHM15 MONO OPERATION! AMPLIFIER DAMAGE

COULD RESULT!

•Check for shorts on speaker leads.

•Check that the volume control on the head unit is turned down low.

•Remove speaker leads, and reset the amplifier. If the Protection LED still comes on, then the amplifier is faulty.

STOP

Amplifier(s) gets very hot.

•Check that the minimum speaker impedance for that model is correct.

•Check for speaker shorts.

•Check that there is good airflow around the amplifier. In some applications, an external cooling fan may be required.

Distorted sound

•Check that the Level control(s) is set to match the signal level of the head unit.

•Check that all crossover frequencies are properly set.

•Check for shorts on the speaker leads.

High squeal noise from speakers.

•This is almost always caused by a poorly-grounded RCA patch cord.

4 ohm

4 ohm

4 -c hannel Amplifier (Operating in Stereo)

4 ohm

YES! 4 ohm

Four 4-ohm speakers, wired in stereo, will present a 4-ohm load to each channel of the amplifier. Most four- channel amplifiers will work well in this configuration.

	4 ohm
	4 ohm
4 -c hannel Amplifier
(Operating in
Bridged Mono)	4 ohm

NO! 4 ohm

Four 4-ohm speakers, wired in parallel to a bridged four-channel amplifier, will present a 4-ohm mono load to the amplifier. MOST FOUR-CHANNEL

AMPLIFIERS DO NOT SUPPORT 2-OHM MONO OPERATION! AMPLIFIER DAMAGE COULD RESULT!

troubleshootingTroubleshooting