日立扫描电镜真空控制电路故障维修和改进

Vacuum Control Circuit of SEM of HITACHI Troubleshoot and Improving

日本日立（HITACHI）公司生产的各种型号扫描电镜在我国的使用量不少,其真空控制电路基本相同,例如S520、S450等系列扫描电镜的真空阀门的驱动级均为一受控双稳态电路,通过二级不同时间常数的延时电路,触发达林顿功率放大级,去推动电磁阀线圈。第一阀门一组电路,电路参数均相同。在此取S520扫描电镜的V1真空阀控制电路加以分析说明（见图1）。该公司电镜的电磁阀是直接带动真空系统的阀门,所以压差大。

More kinds of the model about the SEM made in the HITACHI are generally used in our country. The vac-uum valves of the S520、S450 series and most Kinds of the SEM in them are directly driven by the electromag-netic valve. So it's strong about the pressure difference and the moment of force, and the circuit of power ampli-fier has to use the high-valt in 100V. And the power amplifier transistor used to be hitten through. This article will introduce to you about the troubleshoot of the circuit and some way to improve them through the analysing.