For the whole professional sound system, the sound quality can be caused by many factors. In order to obtain a perfect performance, it is necessary to check the equipment in advance. During the test process, the sound quality of the speakers can be checked more accurately with the help of professional equipment. In the last two issues, we learned the observation and inspection method and the groping method. Today, we introduce the static parameter measurement method.

The measurement of static parameters must hold the maintenance manual of the equipment produced by the manufacturer, indicating the static working current or voltage at the terminals of each component. Use a multimeter to measure the current, voltage or resistance of each department of the circuit to see whether it is consistent with the nominal value.

1. Voltage measurement

In the process of making this measurement, the influence of the internal resistance of the multimeter on the measurement value should be considered. It should be noted that the static measurement value is different from the dynamic measurement value (when adding signals). Measure whether the voltage of each transistor pin, resistance and capacitor terminal is consistent with the nominal value in static state. The relative voltage of transistor pin can determine whether the tube is damaged.

2. Resistance measurement

Use the ohm scale of the multimeter × 100 or × 1K gear, do not use R × For 10K gear, since 22.5V battery is connected in the upper ammeter, the transistor measurement is different, and the transistor is easily damaged. Measure when power is off. If there is charging capacitance, it must be fully discharged with an insulated screwdriver. One end of the resistance in the measuring circuit must be welded open, otherwise the measurement is incorrect.

3. Current measurement

When using direct measurement, connect the ammeter in series into the circuit to check the current. When using indirect measurement, measure the voltage at both ends, remove the voltage value with the resistance value, and then obtain the current value.