First, the power amplifier work environment
1, the user should place the amplifier in a dry, ventilated place, avoid moisture , high temperature, corrosive fumes from chemicals in the work environment .
2, the user should be placed in the amplifier safe, stable , easy to fall countertop or cabinets used to avoid collision damage or fall on the ground, will cause more damage to the machine or man-made disasters , such as fire, electric shock, etc.
3, the user should avoid amplifier serious environmental electromagnetic interference , such as fluorescent ballasts aging radiated electromagnetic interference will cause the machine CPU program confusion, cause the machine does not work.

Second, the power amplifier power requirements
1 , power on normal user should carefully read the instructions before use , to ascertain the operating voltage of the machine , to avoid damage to the machine with the wrong voltage , resulting in unnecessary trouble and consequences.
2, according to the needs of the international market , in order to meet the needs of foreign customers , some models such as the Grand Hyatt amplifier : F128A, APPLE, SW10, SW12 and others have two or more operating power. AC 115V/60Hz respectively and 220V/50Hz, so check before users in the use of the machine 's power switch to select whether the state matches the voltage of your listening environment , or they may damage the machine , not the normal playback.
3 , China's civilian power with AC 380V/50Hz and 220V/50Hz generally two types, but we generally use home amplifier supply voltage are AC 220V/50Hz, please be careful not to plug in the machine 's 380V/50Hz use the power outlet , do not place the machine power selection switch 115V/50Hz stalls , or they may damage your machine.
4 , for some voltage instability region should increase exchange regulator power supply fixed voltage surges to avoid damage to the amplifier .

Third, the amplifier requires a connection with the band planted
1, the amplifier output and the speaker connection polarity to be consistent, otherwise it will affect the audio amplifier output curve , so that the phase and the sense of hearing the sound source is changed .
2 , the connection between the channel and speaker placement to be correct, otherwise the amplifier for audio reproduction orientation disorder will occur , thus affecting the auditory effect .
3 , amplifier speaker load impedance, power nominal value should be chosen and amplifier output impedance and power of the nominal value of the same or substantially close to the amplifier for audio reproduction to get better performance.
4 , avoid overloading the machine , and audio distortion caused by excessive , causing damage to speakers or amplifiers due to overloading , excessive current and burn.

Fourth, the requirements of the amplifier for audio
1 , available to more audio power amplifier , such as CD players, VCD machines , LD player, DVD player , etc., but we require audio performance must be well , otherwise it will cause the audio output of the self-excited DC or other adverse signal to the amplifier inside , causing damage to the amplifier .
2 , audio amplifier audio connection requests on the analog input terminals must be in good contact , otherwise it will cause buzzing sounds constantly issuing from the speakers , and even damage to the speakers or amplifiers. If the source is a fiber optic cable fiber optic cable must ensure good contact with the fastening and machine port , or digital audio will not be played.

Fifth, the amplifier under normal operating conditions and time
1 , power amplifier working condition power source and the load that speakers are three indispensable , we require work on the master volume amp maximum undistorted output third state, but need to be adjusted appropriately.
2, the machine working time generally require continuous play four hours later, must be shut down for 30-60 minutes before re-use , otherwise it will be too long for some components using heat damage .
Three , karaoke OK amp maintenance
Kara OK PA common faults are: no output , AC or noise, output fault small voice, distorted , OK no output , OK self-excited and can not decode and so on. Repair method described separately below :
One , no output fault repair
Amplifier has no output failure may have the following reasons:
A, power supply failure: failure of power supply performance indicator , the display is not lit , no output all channels .
Repair method is to start checking the fuse is blown , the power switch contacts are burned out. The two cases because the machine has a large capacitor filter circuit in the boot of the moment due to the impact of the formation of the charging current can sometimes make the fuse blows or the power switch contacts burn out , you can use a multimeter ohm test plug ends hands to indicate to a few ohms as normal, you can also use a multimeter test transformer secondary voltage profile discharge voltage , if the test sub- discharge voltage is 0V, internal transformer may be open , if the measured voltage is normal , positive and negative rectifier output voltage is 0V may be damaged bridge rectifier or rectifier .
B, the protection circuit relay does not pull, disconnect the speaker while still pull amplifier circuit may occur DC , abnormal working conditions , will cause the amplifier output DC -bit offset , or tube amplifier output current is too large , will cause the protection circuit relay does not pull, the amplifier has no output . Cause the amplifier output voltage is not normal many reasons : If the power supply circuit of a filter capacitor deterioration failure , leakage, an arm of the bridge rectifier diode performance is poor, resulting in positive and negative voltage asymmetry, because the amplifier circuit is generally full DC coupling circuits, circuit elements may cause any change in the output voltage is not normal .
If the protection circuit itself can also cause failure of the relay does not pull, the amplifier will be no output . However, this happens much, check the protection circuit should generally focus on examination of each of the circuit transistors, diodes is normal, if there is leakage and other capacitor . Another relay contacts burned or bad , will cause no output failure.

Second, hum or noise is a big overhaul
Power amplifier hum large fault occurs generally:
A, power supply filter circuit fault : When the filter capacitor failure or capacity becomes very hour , there will be bad filtering , power supply filtering large , resulting in hum . Sometimes accompanied by low-frequency filtering undesirable self-excited sound. If only the positive or negative side of the power supply filter capacitor failure will result in positive and negative supply voltage asymmetry , and even cause the protection circuit, the relay does not pull .
B, when there is an arm bridge rectifier circuit , the fault phenomena and filter capacitor failure similar phenomenon is hum increases, small-signal still capable of playback , the volume appears slightly larger signal blocking or protection circuit .
C, input circuit causing hum is entered by the input jack , it is generally just unplug or turn down the input line input level control volume can be eliminated . Resulting in the input circuit is usually the cause hum input signal line shield wire break or input signal itself, the quality is poor, this situation should change a good quality signal line to try.
Big noise amplifier failure usually have the following situations:
A, random noise that is a regular "click ... carbazole ... " sound, kind of condition is generally short-circuit or circuit board components caused by moisture leakage . If the input coupling capacitor leakage , leakage compensation capacitor or the input of a transistor amplifier circuit poor leakage between internal electrode , there may be caused by poor soldering components . Also there will be a "click ... carbazole ... " sound , in which case if gently tapping case , they will be issued with the knocking noise .
B, the other one is the continuous " sand ......" sound, a noise within the input transistor of the amplifier circuit caused by defective products .
C, there is a self-excited noise. Low-frequency noise can be divided into self-excited self-excited self-excited noise and high frequency noise .
Low self-excited low frequency noise , such as " Poof ...... " sound and the " beep ...... " sound , low-frequency noise is the noise from the excitation frequency is low, usually due to the filter capacitor failure or poor performance caused by power supply power adapter resistance increases cause.
High-frequency self-excited high frequency noise is self-excited noises, such as high-frequency whistling and so on. Multi -frequency self-excited or unstable for a solution transistor input and output lines are too close , there may be compensation capacitor failure or deterioration caused .
D, there is a noise is due to poor contact caused by the potentiometer . This failure is characterized by a rotating potentiometer will be " rattling ...... " sound, or sound occurs when the big small phenomenon , replace potentiometer or potentiometer after cleaning with alcohol could be resolved, such as our ML-585 Kara OK some adjustment potentiometer will sometimes encounter this situation.

Third, small voice, output shortage Troubleshooting of gain reduction
If the input signal is normal , but a weak signal only output amplifier , speakers sound small tube amplifier output may be due to excessive current being burned , or the emitter resistor burned, driven only by a small tube output directly signal. Another case is the volume encoder may use a long time , the oxidation of poor contact volume control or input board coupling capacitor failure , an integrated IC damaged front panel , etc., may cause small voice, gain down such failures , check this fault segmentation method is the best method and signal injection method , fast and accurate detection speed .

Fourth, the distortion fault repair
When the amplifier distortion , we can according to the fault analysis of the phenomenon .
A, a situation is when the sound is very small, audible signal distortion is large, voice of the broken, there is a sense of obstruction , but the output is large, the sound is relatively normal. This one is the output tube amplifier quiescent current is too small due to crossover distortion . This phenomenon may be bias circuit transistor performance deterioration caused by poor or . We can check the multimeter electrical barrier transistor amplification or substitution method to solve such failures.
B, there is a self-excited circuit amplifier distortion caused in this case , the output signal associated with self -excited calls, so that the output sound becomes ugly, we can change the anti- self- excited circuit capacity to resolve the class of phenomena .
C, should also note that , when there is sound distortion , you should make sure the distortion caused not by the speaker before overhaul on the amplifier .
Sound system distortion is sometimes caused by the speaker . If the sound is often made ​​of sand bass speaker unit failure , the sound muffled tweeter is generally caused by burning .

Five , karaoke OK electrical performance failure
Kara OK No output failure:
A, Kara OK without causing a situation Kara OK output switching circuit can not be opened , this situation is often Kara OK switch is damaged or can not get the switch control signal is applied .
B, the other is the front end circuit IC4558 OK OK circuitry is damaged or not working properly. Generally detected by the voltage method , a more intuitive and accurate .

Kara OK self-excited , no reverb failure:
A, Kara OK OK self-excitation may be used by external components caused by reverberation manifold , such as capacitance wrong, capacitors false welding and so on.
B, Another case is the reverberation manifold itself can also cause damage to self-excited Kara OK and OK to reverberation failure. If the reverb circuit 5V power supply can also cause abnormal Kara OK without reverb.

Six , the decoding circuit fault and Precautions
A, after decoding circuit may cause damage to the fiber no output , coaxial no output , the output sound intermittently blocking other undesirable phenomena. But decoder board properly, causing no signal digital port many reasons . If the DVD is set incorrectly, optical output port signal is turned off , the fiber glass lens off or plug thread and poor will lead to optical fiber, coaxial no output failure.
B, DTS DIGITAL SURROUNDTM discrete 5.1 channel data is audio format can be recorded on CD, DVD and LD , but most of the CD, DVD or LD player can not decode and playback. For this reason, when DTS-encoded software is played from a CD, DVD or LD player's analog output noise will appear great .
C, if the player's analog output amplifier directly connected to the analog input port , there will be a great noise , there will be the possibility of damage to the audio system , in order to avoid possible damage to the audio system , the user should take proper measures in connection .
D, to enjoy DTS DIGITAL SURROUNDTM play program , an external broadcast programs with DTS DIGITAL SURROUNDTM decoding systems such as : ML-787, M66, M88, ML-585, etc. to be connected to a CD, DVD or LD player 's digital output (S / PDIF or TOSLINK).
Reset several typical methods of operation amplifier
If the result of certain factors cause the machine not working , please do not rush to repair the machine to be diagnosed after a system reset before the machine is faulty repair process .

The following models of the system reset for each of its methods :
1, ML-787 models
In the case of the microphone is not inserted , while holding down the panel MIC VOL- and DIRECT button on the remote control or press and hold GrandHigh Standard key until the screen displays GRANDHIGH STANDART ( Grand Hyatt standard ) , the system restore all data to factory settings .
2, ML-383I models
While holding down the panel MIC VOL- and EXT511 key until the screen displays : FACTORY ( factory ) , the system restore all data to factory settings .
3, ML-383 models
While holding down the panel MIC VOL- and MUTE button until the screen displays : FACTORY ( factory ) , the system restore all data to factory settings .
4, ML-585 models
First the machine power switch off, then press and hold the panel SPK SEL key, then the machine's power switch is turned on , until the display shows RESET ( reset ) when the SPK SEL button is released , the system restore all data to the factory settings.
5, DM868 models , DM838 models , DM858 models are equipped on the remote system reset button , Unknown See instruction manual.
6, C388 and C288 amplifier, the remote control has a reset button .