电源灯亮表明供电稳压电路正常。先用一导线短接继电器RY的常开接点,然后按正常程序通电试机发热盘EH发热正常。恢复接线,通电仔细倾听仍无继电器吸合声,表明可能为继电器损坏或无工作电源。实测集成块IC3{8}脚为高电平正常,但三极管BG1 b极电压为零。怀疑与R1相接的接插件接触不良,拔下插头另加检修延长线后测b极电压仍为零,查R1电阻已开路。用2kΩ电阻更换后,恢复正常。 |
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