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例1 故障现象:射频输出时,有伴音无图像。速修:该机射频调制输出盒的图像载频电路以D_1(2SC636三极管),D_1(2SC636三极管)和D_3(2CD1215R三极管)为主要元件。此时用示波器测量D_1的基极,出现了视频信号输入波形。转而测量D_2的发射极时,没有发现正常的信号波形。往回测量D_1的发射极时,出现了视频信号波形。这说明以D_1为主的前置放大电路之工作是正常的,故障原因是D_2坏。
Example 1 Symptom: When the RF output, there is no sound image. Speed ?? repair: The aircraft RF modulation output image carrier frequency circuit D_1 (2SC636 triode), D_1 (2SC636 triode) and D_3 (2CD1215R triode) as the main components. Oscilloscope at this time measuring the base of D_1, there has been a video signal input waveform. Instead of measuring the emitter of D_2, no normal signal waveform was found. When the emitter of D_1 is measured backwards, a video signal waveform appears. This shows that the D_1 based preamplifier circuit work is normal, the cause of the malfunction is D_2 bad.