二、CPU键扫描电路和系统功能设定电路常见故障造成这部分电路故障原因主要有两种;一种是因虚焊、接触不良、元件开路性损坏和矩阵电路的印刷电路(铜箔线)断裂而引发的开路性故障;另一种是因键开关触点之间漏电、矩阵电路中印刷电路之间漏电或它们对地漏电,以及元件短路性损坏而引发的短路性故障。对于系统功能设定电路来说,不论是开路性故 Second, the CPU key scan circuit and system functions to set the circuit common fault caused this part of the circuit failure causes are mainly two; one is due to Weld, poor contact, open circuit damage and matrix circuit printed circuit (copper foil) Open fault caused by failure; the other is due to key switch contacts between the leakage, matrix circuit leakage between the printed circuit or their ground leakage, and short-circuit damage caused by the components of the short-circuit fault. For the system function setting circuit, no matter it is open circuit