故障现象 :显微镜上、下运行不受控制 ,在工作时 ,用脚踏住向下运行的按键时 ,显微镜头从上向下运行至中线刻度时 ,不再继续运行。当用手将显微镜头调至底线刻度时 ,通电后 ,显微镜会自行向上运行至中线刻度。调节放大倍数的焦距控制按键时 ,焦距能自由调节。分析检修 :通过以? Symptoms: The microscope is not controlled by the up/down operation. When the user presses down the button that is running down when working, the microscope head will continue to run from the top down to the midline scale and will not continue to run. When the microscope head is adjusted to the scale of the bottom line by hand, the microscope will run up to the center line scale after the power is turned on. The focal length can be adjusted freely when adjusting the focal length control button of the magnification. Analytical overhaul: Through?