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[例1]故障现象 手机和台机不能互相呼叫。 分析与检修 有关SN-738/739型远程无线电话机的电原理图请参见1993年《电子世界》第10期和第11期。经询问机主,该机故障是由于雷击造成,所以应从台机电源开始查起。先检查12V和8V电源,正常。按下CALL传呼键时,CALL指示灯不亮,可断定发射电路振荡、推动部分没有供电电压。按下CALL键不放,测量Q11集电极和发射极,均无电压。测Q8,基极无电压而集电极有17V电压,可判断R65断路或C36、D8短路。经测试,D8短路。换上新的12V稳压管,开机,CALL指示灯一直亮。再测Q11和Q12,发现Q11发
[Example 1] Symptom Handset and desk machine can not call each other. Analysis and Overhaul For the electrical schematic of the SN-738/739 Remote Radiotelephone, please refer to Issue 10 and Issue 11 of Electronics World 1993. After asking the owner, the aircraft fault is caused by lightning, it should start from the machine power check. First check the 12V and 8V power supply, normal. Press the CALL page button, the CALL indicator does not shine, it can be concluded that the transmission circuit oscillation, there is no power supply to promote the voltage. Press the CALL button, measured Q11 collector and emitter, no voltage. Measured Q8, the base voltage without voltage and the collector 17V voltage can be judged R65 open circuit or C36, D8 short circuit. After testing, D8 short circuit. Put on a new 12V regulator tube, boot, CALL indicator has been bright. Retest Q11 and Q12 and found Q11 hair