How To: Make a CRT TV Into an Oscilloscope

This is the simplest possible way to make a CRT (cathode ray tube) TV into an oscilloscope, it can be done in about half an hour.

Supplies
-A CRT TV (color may work, but I'm not sure)
-Some wire
-A soldering gun
-Rubber gripped pliers (for safety)
-A screw driver

Step 1: Identify Wires

After undoing all screws remove the cover from the TV.
Inside wrapped around the CRT are two coils of wire, one controls the vertical deflection of electrons, the other controls the horizontal deflection.
Find where these coils of wire attach to the circuit board, and desolder one coil.
Place the cover back on the TV(for safety) and plug in and turn on the TV.
If you see a horizontal line, you desoldered the vertical deflection coil.
If you see a vertical line, you desoldered the horizontal deflection coil.

Step 2: Placing Wires

Desolder the vertical coil if you haven't already and attach extra wire to the vertical coil, this will have to be long enough to come out of the TV so you can attach a voltage source.
Now desolder the horizontal coil, and solder it to where the vertical coil was.

Step 3: That's It

Really, it's an oscilloscope now.

Step 4: How to Use It With Music

I use mine to watch the waves created by music from my mp3 player
First take an old pair of headphones and cut one off, then strip away some of the insulation.
Now you should have multiple exposed wires, one will be slightly thicker than the others and wll have a thin coating of insulation on it - scrape it off.
Attach this wire to one end of the vertical coil, and the small group of wires to the other end.
Now plug it into a sound source, remember your attaching your mp3 player (or whatever) to a giant coil of wire, and there's chance it could break.

Comments

[DianaBarra]

Does anyone know how to turn off the TV timer? After a few minutes the oscilloscope turns off :(

[Martheus]

Some newer colored CRT TVs like Samsung are checking if everything is fine before the power on, so if TV is on and screen is black, it could be this problem (TV finds out that coil is not connected and it shouldn't start the screen). I solved it with stereo-switch between normal coil wiring (TV checks if coil is connected, no matter what coil) from TV board and input wiring. If so, switch to normal wiring, power on TV and after screen is on, switch to the input wires and it should work as described oscilloscope/music visualiser. Maybe it should work with some resistor connected between the coil wiring on board too...

[app0]

Hello, nice instructable!
But I want to make a multi-mode oscilloscope out of my old TV, so I can use it as a usual oscilloscope and as an X-Y oscilloscope.
How do i do that?

[Fixitfelix007]

Make a 2 channel amplifier. Check both vertical and horizontal deflection coils for impedance with a multimeter (ones usually more than the other) even it out with a high watt resistor in series.
Then connect one channel to each coil and viola!
Oh and put a double pole double throw switch on the horizontal coil (center taps to coil, position 1 to 60hz from board, position 2 to your amp) now you have a X-Y that can also switch to a single channel waveform.

[DWinker]

I'm really not sure....don't even know what that means actually, sorry I can't be more help.

[app0]

That's me again here after a year lol, I finally found a TV that I want to use, but, do i really have to switch the horizontal coil to the vertical source, or i can just connect the horizontal one to the sound input and get a vertical line? Don't really feel like messing with HV stuff :p

[DWinker]

I never thought of that. I tried hooking the sound input directly to the vertical coil and the distortion was awful.
Unless you have another plan for the tv your idea sounds like it's worth a shot (and if it works that would be really cool).
Also, just for the sake of info, the coils aren't the HV part. The only HV danger with this is that you have to stick your hands inside the tv to do any of this stuff.

[shomas]

I think a CRT's normal vertical sweep (picture frame) is 30 hz, and 525 horizontal sweeps per picture frame making the original horizontal sweep sweep 30*525=15,750 times a second. With the CRT's vertical sweep serving as the new horizontal sweep, a 600 hz signal will look like 20 wave cycles on the screen and a 1200 hz like 40 wave cycles.

On the other hand using 15,750 sweeps per second, will not display most audio frequencies well. A 600 hz single will look roughly look like 26 mostly horizontal lines moving to right (i think). But, If you want to inject a 60 khz single with a 15,750 hz sweep, it will look like 3.8 waves cycles.

[app0]

OK so I killed the TV in process lol.
Then I got a Mac classic with a bad logic board.
In process broke its vertical sweep generator somehow
So now ended up with this:
http://www.youtube.com/watch?v=ye3nyxc_MOw
http://www.youtube.com/watch?v=F0i6A2QjdBw

This was before the generator died:
http://www.youtube.com/watch?v=Fn_st_sX9fw

So now it's basically an XY scope, just need some filters and a second amp for the second channel, currently coils are connected to a mono amp with one channel.
Thanks for the i'ble!

[DWinker]

So THAT's an xy scope! It looks great!

[app0]

Well, I just need a visualizer looking like a scope so if it looks like a sinewave or etc. but not precise thats ok lol.
I'll give it a try soon and post the result

[Annnnnnnnn]

VERY IMPORTANT ALERT !!

Be careful about the ELECTRIC SHOCK.
Television is one of the most dangerous devices found in homes because of its HIGH VOLTAGE. Even when it is turned off, there may be some capacitors that are charged.
So be careful about the electric shock that can be fatal. Even air can flow the electricity when, the voltage is high enough.
So, when working with HIGH VOLTAGE EQUIPMENTS, SPECIAL INSTRUCTIONS SHOULD BE CONSIDERED.
Always close the cover of the television and stay far from it before you plug in it to the power.
Use plastic shoes to reduce the risk of electric shock.
And ...
For more informations please read:
https://www2.lbl.gov/ehs/pub3000/CH08/LBNL%20Electrical%20Safety%20Manual.pdf

[gc30]

Hello there,

I followed this how to and came up with a kind of working version (see attached video or https://www.instagram.com/p/BfRmjNyFkJR/?taken-by=mightlife). But as you might notice, the waves are quite small in comparison with the screen size and, in fact, the Behringer mixer which is providing the output signal, is maxed out, as is the synth that is being input.

Any ideas what I might be doing wrong?
TV - Westinghouse Sylph 12 (probably from the '70s, if not before)

Mixer (from Main outs) - Behringer Eurorack UB1002

It's certainly not at the stage where I can plug in an mp3 player, the signal would be far too low.

Any help is much appreciated,

Thanks and have a good day :)

G

[DWinker]

It looks almost like an XY oscilloscope (neat!), are both coils connected to audio signals?

As for the size, my CRT scope only used a fraction of the screen - the output was tiny. This instructable might be of use though https://www.instructables.com/id/Fully-Functional-...

Best of luck!

[Lola43210]

Hi ..?
This is the third TV burnt !! ?
It was showing that line and then after 7 minutes suddenly disappear! it is happening every time
Why that does not work with me?
The TV is working but the screen is black.
The horizontal coil supposed to handle the 60hz what is the wrong ?
I even could not try that circuit you suggested ...

[DWinker]

Sorry I took so long to respond! And I'm sorry about all the TVs; that's too bad.

The TVs don't work at all any more? And does anything actually burn? Do any components inside look like they failed?

Moving the deflection coils shouldn't make anything change in a way that would break the TV

[Lola43210]

no problem
actually I finally did it! and I find out what was the problem
thank you very much for your help :) and your instructions.

[TimS397]

Hello! I think I got the same problem as you at the time.

I can't get no line or point... The Tv is on, but the screen stays black. On the front panel the led blinks, wich is not habitual...

Do you have any idea? Is my Tv not old enough? I tried on 3 different TVs and only on of them works just fine (apparently the oldest one).

Thanks!

Tim

[DWinker]

Woohoo! I'm glad to hear that.

[JasonP155]

Try connecting a "dummy" coil to the disconnected output. Try to choose a coil of similar impedance to the yoke. (1-2mH, 5-10 ohms).

Next time try using a small black and white unit. The simpler the better.