DIY Single-Axis CRT Oscilloscope

I’ve always been fascinated by old-school oscilloscopes,

So I decided to build the most basic oscilloscope I could – one that only moves in the Y axis. No math, just a CRT, some analog circuitry, and a bit of trial and error.

It doesn’t display waveforms like a full oscilloscope, but it does visualize analog signals in real time – and it looks awesome doing it.

It’s a great beginner project for anyone who wants to understand how CRTs work and how analog signals behave.

Note: You cannot leave exposed wires inside the TV. Use electrical tape to protect and insulate all connections.

Basic Tools & Equipment:

1. Soldering Iron
2. Soldering Wire
3. Screwdrivers
4. Alligator Clips
5. Welding Gloves / High Voltage Gloves (recommended for your safety – I’m using cheap welding gloves)
6. Old CRT TV (single color only)
7. Electrical tape

Signal Source:

1. Signal Generator (can be a function generator, a simple transistor-based oscillator, or even your computer running a tone generator)
2. AV Audio Output Jack
3. Shielded AV Cable (recommended for noise reduction, but a regular one works too)

1. Unplug the TV.
2. Safety first – always.
3. Lay the TV screen-down
4. Use a soft towel or cloth to protect the screen.
5. Remove all the screws on the back panel.
6. Usually 4 to 8 screws. Some may be deep – use a long screwdriver.
7. Lift the back cover carefully.
8. Pull it gently upwards and back.
9. Some models may have wires connecting to the back shell.
10. Done.
11. You now have access to the inside.

All the technical terms mentioned in this step are illustrated in the image.

At this point, put on your insulated gloves for safety.

Connect one end of the alligator clip to a screwdriver, and the other end to the point where the black ground wire is attached to the metal frame of the CRT tube (refer to the image).

Carefully slide the screwdriver under the anode cap and make contact with the metal terminal inside. Tap it several times to ensure proper discharge.

A visible spark may occur — this is expected.

After confirming that the charge has been safely discharged, you may remove the gloves and proceed with the next steps.

1. Set your multimeter to continuity mode (usually indicated by a diode symbol or sound wave icon. if you dont have a Multimeter you can use an LED connected with one leg to batteries and to use the other wires as probes).
2. Locate the four wires coming from the deflection yoke on the neck of the CRT.
3. Test continuity between wire pairs:
4. Place the probes on each possible pair of wires.
5. When you hear a beep or see continuity on the meter, that pair forms a coil.
6. You will find two pairs with continuity: one is the horizontal (X) coil, the other the vertical (Y) coil.
7. Cut one Pair of Wires in thier middle
8. Connect The TV to Power and turn it On
9. if there is a Vertical line on the screen leave the wires disconnected
10. if there is a Horizontal line on the screen solder the wire Back and cut the Other Pair

Step 4: Connecting the Output Jack

1. Take the output jack and solder the wires you disconnected in Step 3 (the X deflection coil wires) to it.
2. If the wires are too short to reach outside the TV case, solder extension wires to the disconnected coil wires.
3. Drill a hole in the TV case and carefully pull the output jack through the hole, securing it in place.
4. That’s it — you’ve just built yourself a basic oscilloscope!