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例1 故障现象:能接收而不能发射,按下发射键,红灯不亮,且无射频功率输出,但液晶屏上功率电平显示正常。分析与检修:若能接收信号且屏显正常,说明微处理控制和显示部分及PLL接收部分正常工作。根据故障现象分析,原因可能有三:一是发射机功放部分消耗电流过大;二是发射指示灯电路电流过大;三是R315阻值变大。因无射频功率输出,首先应查PTT,开关按下时发射机是否有电(测PA01与连接插头J201上T5端,正常为4.5V1如果电压正常.则是发射部分有故障;如果电压不正常,可能是Q236损坏或R315阻值变大所致。其相关电路如图1所示,检查晶体管Q236、Q235、
Example 1 Symptom: can receive and can not launch, press the launch button, the red light is not bright, and no RF power output, but the power level on the LCD screen shows normal. Analysis and Maintenance: If you can receive the signal and the screen is normal, indicating that the microprocessor control and display part and the PLL receiver part of the normal work. According to the analysis of the phenomenon of failure, there may be three reasons: First, the transmitter power amplifier current consumption is too large; Second, the emission current LED circuit is too large; Third, R315 larger resistance. Because there is no RF power output, first check the PTT, when the switch is pressed, there is power on the transmitter (PA01 and connector plug J201 on T5, normal 4.5V1 if the voltage is normal, then there is a fault on the transmitting part; if the voltage is not normal , Q236 may be damaged or R315 resistance due to its related circuit shown in Figure 1, check the transistor Q236, Q235,