Analysis of the reasons for the large brightness difference between the two lines of the SR-8 two-wire oscilloscope

　　1. Improper use
　　
　　, such as the position difference between the brightness knobs of the two lines is too large; the Y-axis or X-axis "attenuation" and "amplification" knob positions of the two lines are far apart, that is, the Y-axis or The brightness of a small line is greater than that of a line with a large gain, or although the amplification amounts of the two lines are basically similar, the amplitudes of their respective input signals are very different, which will also cause a difference in brightness between the two lines. These are all operational problems and generally not faults of the instrument itself.
　　
　　2. The performance of the two electron guns of the oscilloscope tube is very different.
　　
　　For example, changes in the cathode emission capability and the grid control capability will cause the brightness of the two lines to be inconsistent. When the brightness of the two lines is seriously different due to the large difference in electron gun performance, the oscilloscope tube should be replaced, or unequal voltages should be artificially applied to the control grids of the two electron guns to obtain a two-line display with similar brightness. In terms of oscilloscope circuits, there are many reasons for the large difference in brightness between the two lines, such as improper brightness balance adjustment; too large a DC voltage difference between the control grid and the cathode; too large a difference in the voltage applied to the accelerating anode, etc. . When checking whether the brightness of the two lines is balanced, you can rotate the Y-axis and X-axis amplification knobs counterclockwise to zero, that is, there is no Y-axis signal and scanning pulse signal on the deflection plate of the oscilloscope tube, and the light trace is only two points. By adjusting the focus so that the two points are the same size, you can determine whether the brightness of the two lines is balanced.