测整机高压供电电路C4对地+305V电压,正常;测低压供电电路c92对地+18V电压,正常;测C91对地+5V电压。正常;测比较器U2B(1)脚输出端对地电压为0Vl正常为+4.9V)测U2B(7)脚同相输入端对地+3.4V电压。偏低(正常为+36V),U2B已由高电平变为低电平。用万用表R×10k挡测同步电压比较电路发现取样电阻R16(470kΩ/2W)变值为600kΩ。更换R16后整机恢复正常。 |
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