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故障现象 每部分机在摘机后都有音乐和拨号的混合音。 分析与检修 每部分机在摘机后都有音乐和拨号的混合音,说明CPU未按程序正常工作,故障范围可能有以下几种情形:1.+5V电源电压偏离正常值;2.无CLK或CLK信号不正常;3.CPU或程序芯片及外围接口芯片损坏;4.交叉网络损坏。 测量CLK信号,发现频率升高且幅值较小,更换4M、0.001μF及7404后,发现CLK信号恢复正常。但此时摘机时又变为无任何声音。 检查CPU、2764、6264、8255和CTC各引脚信号,均正常;然后测量CTC有INT信号,而CPU此时无INT信号,
Symptom Each unit has a mix of music and dial after off-hook. Analysis and maintenance of each machine in the pick-up after the music and dialing mixed sound, indicating CPU does not work according to the program, the fault range may have the following situations: 1. +5 V power supply voltage deviates from the normal value; 2. No CLK Or CLK signal is not normal; 3.CPU or program chip and peripheral interface chip damage; 4. Cross network damage. Measuring CLK signal, found that the frequency increases and the amplitude is small, replace 4M, 0.001μF and 7404 and found that the CLK signal returned to normal. But at this time it turned out to be without any sound when off-hook. Check the CPU, 2764,6264,8255 and CTC pin signals are normal; then measure the CTC INT signal, and the CPU at this time no INT signal,