测整机高压供电电路c4对地电压为+305V,正常;测低压供电电路EC92对地电压为+18V,正常:测EC91对地电压为+5V,正常。测比较器U2B(1)脚输出端对地电压为0V(正常为+4.8V),测U2B(6)脚反相输入端对地电压为+0.8V偏低(正常为+3.8V)。用R×100挡测LM339外围电路及元件均正常,判定LM339已损坏,更换LM339后整机恢复正常。 |
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