Family choice and use of power

Pa - performance index

The main performance indexes are amplifier output power and frequency response, the distortion degree, signal-to-noise ratio, output impedance, damping coefficient, etc.

Output power: unit for W, because each manufacturer of measurement method is different, so some names of different way. Such as the rated output power, maximum output power, music, music peak power output power output.

Music is refers to the output power: the distortion degree does not exceed the specified under the condition of the music, the moment signal amplifier maximum output power.

Peak power: refers to the distortion of the conditions, not to the maximum volume will power amplifier, the maximum output power can music power.

Rated output power: when the distortion degree for 10% of the average output power. Also called the most useful power. Generally speaking, the more power, peak power of music, music power than the average power rating peak power power rating is about 5-8 times.

Frequency response: amplifier frequency range, and the frequency range of evenness. Frequency response curve of the flat or general use decibels [db] said. Household HI - FI amplifier FRF 20Hz is generally positive 1db 20KHZ - the range is wider. Some of the best power amplifier FRF have 0-100 KHZ.

The distortion degree: ideal amplifier should be the input signals and no change after the faithful reduction. But due to various reasons the amplifier amplification of the signal and the input signal, often compared to produce different degrees of distortion, the distortion is distortion. In percentage terms, the numerical 55x55mm are. HI - FI amplifier in total distortion. 03% - 0. 05% between. The distortion of the amplifier is harmonic distortion, intermodulation distortion, cross cutting wave distortion, distortion, the transient distortion, the transient intermodulation distortion etc.

Signal-to-noise ratio (SNR) : refers to the signal level with the power output of various noise level than with the values, said db. Average household HI - FI amplifier and signal-to-noise ratio in 60db above.

The speaker output impedance: the equivalent resistance, called output impedance.

Power - the breakdown maintenance

HI - FI acoustics and AV amp common faults have no job, no sound engine output, sound, light, distortion, noise and screaming, etc.

The overhaul of fault introduces below and repair skills.

Machine doesn't work

The work is not the fault that the amplifier without any, each function keys are failure, nor any sound, like an electrified.

When first check the power supply circuit. Available on both ends of the power plug multimeter measure dc resistance (the power switch should connect), normal when hundreds of ohm resistance. If the measured resistance, and many smaller power transformer, severe heat power transformer is the primary windings of local circuit, If the measured resistance to infinity, should check whether the fuse, whether the primary winding transformer fusing between power and plug, without break. Some machines increases the temperature in power transformer protection device, the primary windings of the meet (usually installed in temperature fuse power transformer, will remove the external insulating transformer can be seen), it can also make damage power transformer breaker primary windings.

If the plug is normal, but energized at resistance measurement circuit each output voltage power is normal or not. For the control system microprocessor or logic control circuit, should focus on the amplifier circuit control of the power supply voltage (usually + 5V) is normal.

If no + 5V voltage, measure the three voltage should be integrated circuit 7805 input voltage is normal, if the input voltage is not normal, should check rectifier, filter circuits. If the input voltage, and 7805 normal output voltage is low voltage or ten 5V, disconnect the load voltage at + 5V can resume normal. If + 5V voltage, fault in load circuit, If the voltage remains unusual + 5V, fault in 7805 itself.

If the system control circuit, the power supply voltage normal + 5V should check the microprocessor and reset signal is normal clock, keying and display driver circuit is damaged.

No sound output  wholesale hi-fi

Silent for various operation fault, have corresponding function keys, but without the condition that signal output.

Maintenance of protective circuit, should see amplifier can absorb after startup protective relays. If no action shall be measured, relay output voltage amplifier circuit midpoint, flow testing whether offset voltage is normal. If the midpoint voltage offset or flow testing, abnormal voltage power amplifier circuit fault, should check is positive, negative power is normal. If the positive and negative voltage asymmetry, can be positive and negative power load circuit with judgment is disconnected, power supply circuit itself is not normal or amplifier circuit fault. If the positive and negative power amplifier circuit, should check each amplification is damaged pipe.

If the amplifier circuit midpoint voltage output and flow test voltage all normal, and protection relay, is no fault in the protection circuit, should check relay drive IC or is damaged, the drive tube detection circuit is normal. If the relay contacts, but can not sound output, should check whether the speakers are normal and relay contacts good contacts, static circuit.

If these parts, reoccupy signal interfere with the normal method of fault is in check before or after the amplifier circuit grade level. Using the multimeter, R x 1 against the red BiaoBi grounding, black BiaoBi fast points after touching the input amplifier circuit, if the speaker has strong ", "kalos cascade amplifying circuit fault in the former stage, If the speaker is no response is the amplifier circuit fault.

For not using peripheral protection circuit of integrated circuit amplifier circuit (usually in integrated circuits have internal thermal protection), can measure the power supply voltage is normal or not. If the power supply voltage signal interfere with the normal, reoccupy check: in the signal power integrated circuit dc input signal, if add.misunderstandings speakers have stronger "and" kalos cascade power integrated circuit fault in normal, former amplifier circuit, If no less, but less related peripheral components and check on the amplifier is normal, integrated circuit itself.

No sound output tube amplifiers, also should check whether the power supply, watching the filament, tube and shell temperature is normal. If the filament is not bright, tube and shell is cool, should inspect pipe filament and power voltage screen is normal or not. If the voltage is not normal, check again -- step into the power circuit shall, when necessary, disconnect the power supply circuit, in order to determine the load is the power circuit fault or load is short. If the voltage is normal, but in the center of the volume of dc concentres jamming signal head to join, if have strong reaction after class, amplifier circuit fault in normal, former amplifier circuit, Conversely, the amplifier circuit fault. But in promoting the grid and input amplifier tube of grid disturbance signal to join, where grade -- add interference signals, the grade is behind the circuit doesn't work properly. For suspicious components (if available) tube substitution of maintenance.

With dolby surround AV amplifiers, decoding function in dolby surround sound if each channel state cubits all silent at the sound track conditions in the power circuit, the normal situation, usually is dolby surround decoding circuits or systems control circuit doesn't work properly. If the surround channels and direct mode are the silent, should check the system control circuit, signal total volume control circuit and choice.

Sound light

Alleged sound light fault, refers to the audio signal transmission in amplifier amplification process, because of a change in the level or put a link to the amplifier is attenuation, decrease or gain power output.

Repair, the first should check whether the sources and speakers available to replace the normal, to check. Then check all kinds of control and switch potentiometer can greaten, volume.

If the above all normal, each part should identify the fault is in the former stage or in class. For a sound track can be light, former the output signal input to the exchange of another channel after class, if the speaker's voice circuit fault, the size of constant level circuit, Conversely, the fault in the former stage circuit.

The cause of the sound amplifying circuit, the main light output power shortage and gain enough two reasons. Used appropriately enlarging the input signal (such as the signal output to radio loudspeaker directly to the amplifier circuit input, change the volume of the radio, observe the power output of the changes which method to judge the cause. If the input signal output increased after the sound is big enough, output power amplifier, just enough to gain lower, should focus on the check relay contacts have contact resistance increases, the input coupling capacitance capacity, reduce resistance increases, the negative feedback capacitor capacity, or smaller feedback resistance increases or open, etc. If the input signal output increased after the sound volume and no distortion, appear to increase significantly after class, the output power of amplifier, should check the positive and negative power amplifier is low voltage (if only a light, but don't sound track inspection power supply, power tube or integrated circuit performance deteriorated, whether large or emitter resistance etc.

Former circuit switch potentiometer, caused by the sound, light, easily find visual inspection can be cleaned or change of its. If suspect a signal coupling capacitance value, can try parallel. Enlarge tube or op-amp integrated circuit performance, usable also substitution of inspection. In addition, negative feedback element has a problem, also can cause circuit gain.

Noise big

Hum, the noise amplifier, induction crackling noise and white noise, etc.

Repair, should be judged from the former stage or noise from the circuit. But the former, the latter signal connection plug, if the noise, fault before smaller magnitude circuit, Conversely, the fault in class.

Hum refers to feeling low, drab and stable 100Hz exchanges, mainly is humming part should be emphatically improper filter, power rectifier, filtering and check pressure components is damaged. Before and after the power amplifier circuit back coupling capacitance virtual welding or failure, also can produce an effect similar to a humming noise frequency oscillation noise.

Induction noise is complicated composition and harsh hum, mainly is the former circuit switching, potentiometer grounding attachment or signals poor improper shielding.

Fires refers to the "continuous cracks", "kaka", in the former stage circuits, should inspect signal input plug and receptacle, switch potentiometer, whether such contact, without virtual welding coupling capacitance and leakage, etc. After the amplifier circuit should check relay contacts are oxidation, input coupling capacitance without leakage or contact undesirable. In addition, the differential input circuit after level tube or a constant-current tube soft breakdown, also can produce similar edm "kaka" noise.

White noise is refers to the rules for "sasha vujacic, usually by level before and after the input level transistor amplifier circuit, mosfet or op-amp integrated circuit performance of the poor, maintenance, the noise of the same specification available components of the multi-chart try.

Distortion,

A distortion of the fault is robustly migration or amplifier amplification level push-pull output level caused by asymmetric work. Repair, can according to the output power amplifier and distortion, to judge the changes of specific failure.

If the distortion of the tube amplifiers and output power (sound light), should check whether the push-pull amplifier amplification tube in an aging, working or output transformer partial short-circuit the imbalance of work, If the distortion at the same time, more power output feedback circuit is the resistance and capacitance value change failure or the cathode bias bypass capacitors short-circuit.

If a transistor amplifier with volume increased and the distortion, should check the stage a transistor is offset (usually working in the protection of the amplifier circuit) or feedback circuit of capacitance distortion, If there are whether volume, fault before distortion of amplifier circuit, should check whether the amplification of working.

Integrated circuit amplifier abnormal voltage or amplifier circuits inside damage, also can cause distortion (no protection circuit machine). |

screaming

Screaming failure is caused by the existence of self-excited circuit, and low frequency and screaming into screaming.

Screaming refers to the low frequency low "poop-poop" or "beep" sound, usually due to a power supply or improper decoupling filtering out screaming at the same time (usually accompanied by hum), check the power supply voltage stabilizer and filter capacitance, decoupling capacitor is open or refund, internal power failure. Integrated circuit performance, power will appear low-frequency fault, screaming at the integrated circuit working temperature will be high.

High frequency of screaming, usually is higher in vibration frequency amplifier circuit failure or extinction capacitance level op-amp integrated circuit performance deteriorated. But the level of power amplifier circuit decoupling capacitor combined isolation ends up back to check and capacity. In addition, negative feedback element damage, or off when that could cause high-frequency positive feedback and high-frequency screaming.