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If you're silly enough to try this, then at your own risk be it!
How to make an oscilloscope out of a television
Yes it's true you can make a (CRT) television into an oscilloscope! But let's get this right - the method here is very simple and produces a dramatic effect, but it's not going to be a highly technical laboratory precision measurement device! Looks good though!
Now before going into details about the method of construction, a safety warning. Televisions are dangerous if you open them up, and opening up a television set without making the correct precautions first can be hazardous. So, before opening up the television you should check that you own it or have the permission from whoever owns it, or it could be risky as the owner of the television might get cross about it! Electricity is also dangerous, so you should be sensible about that too.
Now, here's what to do:
1. Locate the deflector coil assembly. This is a big coily thing which is all around the neck of the television tube. Or to put it another way, the tube neck is right in the middle of the television, and the deflector coil assembly is around it and further forward.
2. Locate the wires going to the deflector coil assembly. Ideally there should be four of them. Two of these are the horizontal and two of them are the vertical.
3. Find out which are which. (Worth taking time to get right rather than guessing, as an unlucky guess can blow the frame output!). To find out which are which, you need to snip the wires one at a time and reconnect them one at a time in turn and see what happens. Symptoms: If either of the vertical are disconnected, then there's no vertical, so you see a horizontal line. And, guess what, if either of the horizontal are disconnected, then there's no horizontal, so you see a vertical line. Special care should be taken not to electrocute yourself.
Having found which two wires are horizontal and which are vertical, now the "construction" begins. This is where the finesse of the simplicity of the design comes in.
4. Disconnect the four wires from the deflector coil assembly.
5. Connect the wires from the deflector coil assembly that were the "horizontal" to the "vertical" supply instead.
6. Connect the wires from the deflector coil assembly that were the "vertical" to a piece of mains flex which you then run outside the box.
OK! That's it! You should now have a horizontal line on the screen, and the display changes according to what you wire the extra flex into. A battery (DC) will make the line go up or down. A bicycle dynamo (AC) will make the line go up and down very fast and so produce a wavy line on the screen. One of the interesting things you can do with such an oscilloscope is to plug it into SOUND. It needs to be quite loud. The output from a guitar practice amplifier or a lounge hi fi will work. This produces a visual representation of the sound in oscillating waveforms.
You can connect the oscilloscope up to all sorts of things to see what the signal looks like. This is what oscilloscopes are about anyway, but they're usually more precise, have a variable time-base, multi-trace, storage, etc, and they look more like the "'scope" icon on the shareware icons page . However, home-made oscilloscopes of the type described in this write-up have the advantage of having a much bigger screen which a much brighter trace and so are more showy. Plus there is a certain smugness which comes of having tamed a television and converted it into something different!
Another similar trick that can be done to a telly is left-right reversing!
Special safety note: On some televisions, there are dangerously high voltages even a while after the set has been switched off. Make sure you find out if the set you are working on is of that type by using a neon screwdriver, rather than the hard way!
Incidentally, these instructions about things such as the "deflector coil assembly" apply only to TV sets which have a CRT (Cathode Ray Tube). The same isn't true of a flat screen TV!