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故障现象:开机“三无”。分析与检修:首先检查电源部分,相关电路如附图所示。打开机盖发现电源保险丝已熔断,说明有严重短路性故障。测厚膜块STR6309,其第①、②脚间电阻为0Ω,判断内部开关管的c、e极击穿,再查看R703有烧焦现象;怀疑Q703损坏使电流过大烧坏R703,但经测量IC703、D705、IC702第①、②脚电阻值均正常。于是怀疑该故障是由行扫描电路异常所致,然而对行输出管和行激励管进行检查均未发现异常,再对电源部分的其它元件进行检查,也未发现问题。分析认为电源块
Symptom: boot “three no.” Analysis and Maintenance: First check the power supply section, the relevant circuit as shown in the figure. Open the cover found that the power fuse has blown, indicating a serious short-circuit fault. Thick film block STR6309, the first ①, ② resistance between the feet 0Ω, determine the internal switch of the c, e pole breakdown, and then check the phenomenon of charring R703; Q703 suspected of excessive current burn out R703, Measurement IC703, D705, IC702 ①, ② foot resistance values are normal. Therefore, it was suspected that the fault was caused by the abnormality of the line scan circuit. However, no abnormality was observed in the line output and the line excitation tubes, and no other problems were found in the other parts of the power supply. Analysis that the power block