How to modify an oscilloscope with a monitor

　　An oscilloscope can intuitively demonstrate the working state of electronic signals. When electronics enthusiasts make electronic circuits, it would be much easier if they had an oscilloscope. One day, when I was sorting out my belongings, I found a black-and-white monitor that had been idle for a long time. I suddenly had an idea. The working principle of the black-and-white monitor's picture tube is similar to that of the oscilloscope, but the specific working method is different. If it is modified, can't it also be used as a simple oscilloscope? So I analyzed, designed, and modified it.

　　1. Working Principle
　　
　　Compare the picture tube and the oscilloscope tube. Both have electron guns, fluorescent screens and auxiliary circuits.

　　The difference lies in the electronic deflection mechanism. The picture tube uses a deflection coil to increase the size of the display screen. The oscilloscope uses a deflection electrode to increase its upper frequency limit. The respective auxiliary circuits of the two are adapted to their respective working methods.

　　The field frequency of the display is 443Hz. Therefore, the operating frequency of the oscilloscope after the modification will not be very high. Try to minimize the circuit changes, as long as it is simple and practical. Keep the circuit board inside the machine unchanged. Use the sawtooth wave of the field circuit to drive the line scanning coil. Use an external audio amplifier to drive the scanning coil.

　　2. Materials and modification steps:
　　
　　A monitor (working well. The circuit is normal), a set of audio amplifiers above 6W, a 100kll potentiometer, a 10μF/50V capacitor, a pair of two-core plug sockets, a single-core shielded wire of one meter, and a small alligator clip.

　　Internal modification: solder the line scan leads, insulate them, solder the field scan coil leads to the line scan coil. Add leads to the field scan coil and solder a two-core plug to the outside of the machine.

　　External attachment: Use a common audio amplifier circuit (as shown in the attached figure), with a power of about 6W, the simpler the better. Solder a two-core plug to the ground of the power output of the audio amplifier, and solder a 100kΩ potentiometer to the ground of the signal input. After a 10μF capacitor is connected in series to the adjustable end of the potentiometer to isolate the DC, solder in a single-core shielded wire about 1 meter long. Connect a small alligator clip to the shield layer, and connect the core wire to the probe.

　　3. Debug
　　
　　After checking the circuit is correct. Connect the amplifier to the two-core plug from the TV. Adjust the TV brightness to the lowest, power on and test the machine. Adjust the brightness potentiometer until the horizontal line on the display is appropriately bright. Use a probe to detect the signal source. Adjust the 100kΩ potentiometer until the waveform is displayed well. For example, the waveform is reversed up and down or left and right.

　　The two leads on the corresponding coil can be swapped. After power off, install the case and the oscilloscope is modified.