1. Measure the crystal oscillator clock: Use a digital multimeter to measure the voltage across the crystal oscillator. If the voltage at both ends is half of the power supply voltage or one end is lower than half of the power supply voltage (more common in a higher frequency crystal oscillator), the crystal oscillator works normally. If one end is higher than half of the working voltage of the power supply, the crystal oscillator is not normal; but whether the frequency of its operation meets the nominal value can be judged by observing the working condition. For example, a VCD with ES series decoder chip, when the 27MHz crystal oscillator is frequency-shifted, there will be achromatic color or the boot screen will be enlarged and achromatic, and the 16MHz of the VCD servo circuit will not match, and the disc will rotate without reading. Phenomenon, at this time, you can try to replace the crystal oscillator.
2. Detection of the reset circuit: This item must use an analog multimeter because the instantaneous voltage response cannot be seen with the digital meter. When measuring, the multimeter is placed in the 2.5V gear, the red meter of the multimeter is used to connect the positive pole of the power supply, the black test pen is connected to the reset pin, and then the power is turned on. At this time, if the hands are slightly oscillated, the reset circuit is normal. Otherwise the reset is not normal. The amplitude of the swing varies depending on the set reset time. The above method is for the low-level reset circuit, that is, when the reset circuit is a normal workpiece, it is the power supply voltage. For the high-level reset circuit, that is, when the reset pin is working normally, it is 0V, then the red test pen is connected to the reset pin, and the black test pen is grounded according to this measurement.
Spherical lens is also called glass bead. It is a solid or hollow glass bead with a diameter of several microns to tens of microns. Its application fields involve various departments such as chemical industry, military industry, aerospace, transportation, petroleum, light industry, medical treatment and so on. It has the characteristics of good surface finish, good light reflection, directional reflection, high impact strength, chemical stability, light bulk weight and so on.
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