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故障现象:选择任意一种工作状态,开机一段时间后,喇叭内均出现很大的嘟嘟噪声,字符显示也忽明忽暗。分析与检修:根据上述现象分析,判断为公用部分的热稳定性能变差而造成的。因为屏显也忽明忽暗,首先检查了电源部分。电源变压器输出三组电压,分别提供给屏显、前级、功放。当故障出现时,各组电压没有明显变化。检测整流、滤波元件均未发现疑点。采用“温差检查法”,用酒精棉球遂个对可疑元件进行物理降温,故障依旧。排除故障在电源部分。然后重点检查功放部分。功放块由45485和功放主件STK4152组成,当用酒精棉球给功放主件STK4152降温时,噪声突然消
Symptom: Select any kind of working state, boot a period of time, there are a lot of beep noise horn, the characters are flickering. Analysis and Maintenance: According to the above phenomenon analysis, the public part of the judge as the thermal stability of the deterioration caused. Because the screen is also flickering, first check the power section. Power transformer output three groups of voltage, respectively, to the screen display, preamp, amplifier. When the fault occurs, the voltage of each group has no significant change. Detection rectification, filter components have not found any doubt. Using the “temperature difference test method”, with alcohol cotton ball then a physical cooling of suspicious components, the fault still. Troubleshooting in the power section. Then focus on the amplifier section. Power amplifier block by 45485 and amplifier main components STK4152 composition, when the alcohol cotton ball to the power amplifier master STK4152 cooling, the sudden noise