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例1 故障现象:功能处于CD状态时,音箱出现较大噪声,而放入碟片放音时,噪声消失。通常,CD机在未装入碟片时,应该由消噪电路电压加至数字电路中处于静音状态,而不会产生很大的噪声。故重点检查消噪控制电路有关元件。此机CD的数字信号处理电路采用CXD1167Q大规模集成电路,(19)脚为静噪输入端。测量(19)脚电压,无论片盒内有无碟片电压均为0V,检查静噪控制电压由N8(插头)⑥脚提供,顺此脚至CXD1167Q的(19)脚间进一步仔细检查,发现此两脚降压电阻(R74)1.5kΩ开路所致。换上同阻值1/4W电阻后,故障排除。例2 故障现象:在正常使用时,显示屏突然无显示,一切功能键全部失效。首先测量显示屏-30V灯丝电压(正常),其他各输出端未见异常,该机CPU采用TMP47C870CN集成
Example 1 Symptom: Function in the CD state, the speaker appeared more noise, and put the disc playback, the noise disappears. Normally, when a CD player is not loaded with a disc, the noise from the noise canceling circuit should be added to the digital circuit to be muted without generating much noise. Therefore, the key check noise control circuit related components. This machine CD digital signal processing circuit using CXD1167Q large scale integrated circuits, (19) feet for the mute input. Measure the voltage of (19) feet, no matter the disc voltage is 0V in the cassette or not, and check the squelch control voltage is provided by N8 (plug) ⑥ feet, then further examine carefully to the foot of (19) of CXD1167Q and find This two-leg step-down resistor (R74) 1.5kΩ open circuit due. Replace the same resistance 1 / 4W resistance, troubleshooting. Example 2 Symptom: In normal use, the display suddenly no display, all function keys all failure. First of all, the display screen -30V filament voltage (normal), the other no abnormal output, the machine CPU using TMP47C870CN integrated