Instructables Project

The purpose of this project was to demonstrate how to make a TV oscilloscope with materials in a Maker Space. My partner Johnson and I chose this project because we found all the necessary materials in our makerspace, and we. Some of these materials included an old CRT TV, a Wii, and spare wire.

Do you need an oscilloscope? “Yes, you need one, if … you really care about electronics. Seeing and therefore knowing what’s going on in a circuit is crucial to understand and perhaps fix it. And especially for my kind of learning it’s the most important tool to understand electronics and getting better in it.”
https://sciencing.com/uses-oscilloscope-5348699.html

Understanding how a CRT TV works is crucial to making an oscilloscope.

My interpretation of how the CRT TV works is as follows: an electron gun shoots an electron beam (picture2) at a specialized screen that captures energy and holds it for a while as visible light. There are electromagnets on the side of the beam that move the beam left and right, and another on top and bottom moving it up and down. If you cut the left and right electromagnet wires, the TV will only show a thin vertical line. Using these electromagnets, we changed the input for the y-axis (up and down) to the output of an aux cord. This will show sound waves as visual waves.

Materials

• Old box TV (non color will work better, but color TV’s also work)
• Multiple of alligator clips
• A simple multi-meter
• A video source (unless your TV can produce white noise video by itself)

Steps:

• The first thing you want to do is check the TV works. If it does, open the TV by removing the screws.
• IMPORTANT: DO NOT LOSE THE SCREWS, tape them to the outside of the box. The inside might look like the tenth picture (below). Do not randomly stick your finger in the TV as there are a lot of sharp and dangerous objects that will shock you.
• IMPORTANT: You will need to discharge the screen. This is important BEFORE you venture inside the TV due to the risk of shock. Grounding is possible by: taking a flat-head screwdriver, connecting an alligator clip to the screwdriver and the other side of the clip to the actual ground plug on the outlet coming from the TV (this also makes sure the TV was powered off). Next, make sure you are insulated from the floor (think rubber shoes, not touching anything with your legs). Finally, carefully slide the grounded flat-head under the rubber cover from picture 6. Once you slide the flat head under the rubber, you should hear a pop, and maybe a small flash of light. Congratulations, your TV screen is grounded!
• Once you have your TV screen grounded, you will need to locate the Y-axis electromagnet. There should be wires connecting the electromagnet to the PCB board. This is your main play area. You can cut these and gain access to a somewhat strong electromagnet and a very strong x-ray tube.
• Trace the wires back, and find the two wires connected to the top and bottom of the tube.
• Cut and strip the correct wires and connect the two wires to the wire of your source.
• Attach your audio source to the newly cut and stripped wires. Your audio source could be an AUX cable connected to a phone playing music.
• Our TV had an unused aux cable input, so we hijacked it by connecting the electromagnet cables to the hot and ground connectors. This means all we had to do to start the oscilloscope was plug in an aux cord to the front of the TV and the back
• The final step is to close the TV with the screws it started with. –if you don’t lose them first!
• We needed to connect a Wii to the TV because ours did not display white noise. If it did, then we would not need it.

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