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A. The visual inspection method

Visual inspection method is to disconnect the power immediately after. Without instruments, meters, with an intuitive feeling, to mobilize visual, hearing, smell, touch and feel characteristics of four kinds, to judge. Check the accuracy of this method, although poor, but, fast, visual inspection method is especially useful for checking the power failure.

First to look. Outside and observe the structure of the machine or parts. Look at key switch, interface, light loose, then board thread without loss, with or without Weld, discoloration, cracks, bursting phenomena, whether the blown fuse, ignition, smoke, deformation, not stuck and other issues, the use of the eyes, to directly identify and judge.

Second to listen. Gently flip the machine or parts, swing swing, listen to the availability of spare parts scattered or screw off the case, whether there is rattle. There are all normal for continuous flip the "creak" sound or "pops" ignition sound (when powered). If these phenomena, the failure may occur in these areas.

Third to smell. Smell with his nose to smell without burning smell, to find the odor source, the fault may release odor out of a place.

Fourth to touch. Touch to feel the transformer casing (after power failure), do not touch the terminals, because sometimes there is a result of a charged capacitor, the voltage is very high, endangering safety. Feel if this is more than the normal temperature, hot, can not touch. Power tube without overheating or cold phenomena. Whether the regulator is not hot or cold thermal phenomena. If these phenomena, the problem may appear in these places.

B. The test method

Heuristics for suspect part of the circuit compared to segmentation, alternative, simulation and other test methods, to find fault lies       , and then excluded. Specific methods are as follows:

a. compared with the failure to find a machine exactly the same type of machine, in the professional equipment using the same machine the left and right channel components, measuring the corresponding part of voltage, resistance, current quantity, coupled with a comparison to find the fault lies .

b. the split will be a part of the circuit and other parts torn off, connect the external power supply, the injected signal, to judge.

c. with a good alternative to replace suspect components, components, or left and right channel components of the change, in particular, the integrated circuit block can be carried out. If the components of change, the machine back to normal, then the problem parts or damaged.

d. analog temperature simulation, using the hair dryer heating, or cooling with alcohol, the temperature performance of inspection, vibration simulation is the use of thin plastic insulated rod tap some of the components, see the circuit working conditions, you can find some of the Weld phenomenon, check the fault lies. This method is generally carried out by the skilled personnel, they are liable to increase the failure phenomenon.

C. The static parameter measurements

Static parameter measurements must hold manufacturers of production equipment maintenance manuals, indicating the various components endpoints quiescent current, or voltage, using the multimeter to measure the various parts of the circuit current, voltage or resistance, to see if consistent with the nominal value.

a. The resistance measurement

To use a multimeter or ohm × 100 × 1K file, do not use R × 10K file, because this file on a 22.5-volt internal battery meter, measurement of transistor inappropriate, easy to damage the transistor. Measurement in case of power failure, if there is a charged capacitor, must be insulated from the cone screws after full discharge. Measuring circuit in the open end of the resistor must be welded, or measurements are not accurate.

b. The voltage measurement

In making this measurement process to consider the multimeter resistance measurement value impact. Static measurements and dynamic measurements (adding signal) is not the same, it should be noted. When the transistor static measurement pins, resistors, capacitors voltage is consistent with the nominal value, the transistor voltage to determine the relative foot tube is damaged.

c. The current measured

When direct measuring, the current meter in series circuit, check the current size. Indirect measurements, measuring the voltage at both ends, remove the electrical resistance of the voltage value, they will have current size.

In addition to the static parameter measurement, it can also use the dynamic test method, the use of the signal source and oscilloscope, signal directly into the inspection, the circuit judge. This approach directly, accurately, and not easy to damage the components, but also on the electrical and mechanical structure adjustment and proofreading.