I've always been interested in Cathode ray tubes, but the one that I got to play with is only the CRT inside an old TV.
One of the many ways in which an old TV can be reused is by converting it into an oscilloscope.
First, I hacked into the TV to see if something interesting could be made out of it.
The above image shows the electron gun which is used to fire the electron towards the fluorescent coated screen and the electro-magnets which are used to guide the electron beam in the right path.
Making some changes to the horizontal deflection coil or the vertical deflection coil, we'll be able to convert it into a basic scope, however, we need to add some impedance matching circuits since the passive element we're handling here has a notable inductance value.
We'll be able to see the waveform of an input voltage given to the Y-axis deflection plate, that'll be the single channel input.
Here are some easy steps to follow:
VDC: Vertical Deflection Coil
HDC: Horizontal Deflection Coil
Firstly, disconnect the VDC and HDC from the main circuit board. Now connect the HDC where the VDC was initially connected in the circuit board. Attach two long wires to the VDC which will be the input to the oscilloscope. Now in case you need more precision, adjust the refresh rate by tuning the presets present in the circuit board.
Upon completing the above steps, once the TV is switched on,
This straight line indicates that the above-performed steps are correct.
Testing the scope with sample input:
With a basic transistor switch input, we can see the ON-OFF transients clearly!
Square wave input
Sine wave generated using PWM from Arduino
Finally, connecting one channel of an audio amplifier to the CRO TV to check the working!
Thanks for reading!