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1、cd928型手机(1)故障现象:开机、关机均正常,但不能入网。 (2)判断检修:拆开机壳,连接好直流稳压电源开机,发现电流比正常手机电流大,测量U220中频处理芯片的供电管Q221、Q222的集电极,开机后无2.75V电压输出,测量+B输入电压正常,手摸U220芯片发高热,分析可能是芯片问题,用热风枪小心吹焊下U220芯片后更换,一切恢复正常,故障排除。
1, cd928-type phone (1) Symptom: boot, shutdown are normal, but can not access the network. (2) Determine overhaul: disassemble the chassis, connect the DC power supply and turn on the power, and find that the current is larger than the normal cell phone current. Measure the collector of the power supply tube Q221 and Q222 of the U220 IF processing chip without a 2.75V voltage output after power- Measurement + B input voltage is normal, touch the U220 chip high fever, the analysis may be a chip problem, carefully blow the U220 chip with a heat gun after the replacement, everything back to normal, troubleshooting.