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.

Comments

[Reallunacy]

Is there a way to know what the max input for voltage is? I am needing an oscilloscope so that I can properly set the gains on my amp. I want to be sure it isn't clipping, but I want to be certain I am not going to just fry the unit once I do this.

[rainman002]

You might have trouble actually seeing the wave shape, as this does not do any sort of triggering or synchronization to keeps the waves in the same spot on the screen. To overcome that, you'd need to tune your amp-input to a frequency multiple of the scanning frequency of the screen (probably by trial and error).

In addition, the high inductance of the coils may affect the output from the amp. Maybe a voltage follower of sorts would help, but I'm not really sure.

[Magnelectrostatic]

Frying it probably won't be a problem, the input just goes to a coil of wire so you would probably need to burn off the insulation for something to break.
But on mine anything over about 1 volt goes above the screen, so I'm not sure if it would be much help (I don't know much about amps).
Hope this helps.

[amit dwivedi]

please give more elaboated idea of making cro from black and white tv and also elaborate about making dual trace cro from the same.give an account as soon as possible.

[ebuzztone]

On color TVs, is it possible to use the RGB colors to add color to the lines, so that for example the incoming sound determines the color of the waveforms? An idea would be to make an automatic switching circuits that switches between RGB combinations. Would that work?

[Magnelectrostatic]

There must be some way. This http://electronics.howstuffworks.com/tv10.htm shows how color CRT TVs work, and the next page tells how they switch the colors (I didn't really understand that page).
So it's definitely possible, it's just a matter of how....
Awesome idea by the way.

[R.A.T.M]

i need help i did what it said to do then i pluged the tv in and herd screeming like a cap charging then when i turend it on a loud pop happend now all the tv dose is scream

[Magnelectrostatic]

Interesting...are you sure you only touched the part of the circuit board where the coils are attached?

[R.A.T.M]

iv found out what happen i dont know howit happen i blew a transister the one that drives the fly back it wont let me post a pictur but right dow the middle and it wass preaty vilent

[Magnelectrostatic]

Weird, if you ever figure it out make sure to comment!

[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?

[Magnelectrostatic]

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

[Jimmy Proton]

A speaker is just a coil of wire but that never broke anything...

[hATEmATH]

it's great to turn the knobs to VoltDIV and timeDIV :)

[bears0]

how can i tell polarity or does it not matter

[Magnelectrostatic]

The polarity doesn't matter. When the polarity is one way the electron beam is deflected up, when it's the other it's deflected down.

[Ora]

I was taking apart the eyepiece for an old Sony Handycam the other day and I was shocked to discover that it had a tiny CRT in it. I immediately knew I needed to make a tiny oscilloscope out of it. Here's the result:

[bears0]

can you make an instructable please, i have one too and would like to know how you did it.

[Ora]

I just followed this instructable. It's the same principle, you just have to identify the vertical and horizontal coils of the CRT, and for mine I used a wall wart to supply power just to the eye piece so I didn't need the rest of the camera to power it.

[CameronSS]

That's quite brilliant, really. Modern cameras all have LCD viewfinders, but there are countless old camcorders out there with CRT viewfinders. There's a giant one sitting on my workbench right now -- I'm quite tempted to hack into it now.

[Magnelectrostatic]

That's awesome! (the fact that there was a crt in there in the first place, but more importantly that you made it into an oscilloscope!)

[manoch_dc]

I Operation and Vertical lose.

[highvoltage]

I build one from a 1992 color TV and it works great! Only took a couple minutes, easiest and most satisfying build I've done in some time! :D

[bobcat504]

i have a sylvania television i tryed to connect one coil to my stero and i kept the outher coil atteched to the main board i turn it on it has one little spot that lights up when my music plays it does nothing

[Magnelectrostatic]

Did you switch the vertical coil with the horizontal?

[bobcat504]

how can you turn a portable small black and white televison into a oscilloscope

[Magnelectrostatic]

If it's a CRT TV, it should be the same method that I used.

[bobcat504]

nice i made my black and white poritable television in to an oscilloscope i had to connect the white and the gray wire in to a coil it works

[bwandice]

This looks awsome, and I have been trying to get my '82 color tv to do this, but I think it might be too new to work. I have figured out which wires coming from the coil assembly are the vertical and which are horizontal. When I cut a vertical wire I saw a nice bright horizontal line, and vice-versa, so this made me think it would be able to work with this particular tv. So after cutting all the wires from motherboard to coil and after soldering the Horizontal wires from coil to where the vertical wires were on the main circuit board, I turn on the tv and there is neither a vertical or horizontal line at all! the Tv is just blank. Wat do?

[Magnelectrostatic]

Odd...Check the wires, if they're hooked up correctly try putting the wires back where they were before (vertical in vertical, horizontal in horizontal) to make sure nothing is broken, then try again, not really sure what to do other than that.

[jerkey]

the vertical of a TV set is 60 Hz (in the USA).  The horizontal is 15,750 Hz.  If you cut the wires for the vertical, you will get a Horizontal line moving across 15,750 times per second.  Music will not be visible because it is lower than this frequency.  If you cut the wires for the Horizontal, you will get either a vertical line or the TV will stop lighting up.

This is because the Horizontal coil is part of the circuit of the high-voltage power supply.  Some TVs will work with the Horizontal coil cut.  Some will not.  If your TV wont work, try connecting a different coil to the wires to keep the mainboard happy.  An easy win is to use the coil from another TV or monitor and zip-tie it off to the side.

If you get it working, you now have a vertical line which repeats 60 times per second.  You can loosen the metal clamp on the coils and rotate the assembly 90 degrees (turn it to the right, viewed from the back).  Now you have a Horizontal line.  You can feed signals into the old Horizontal coil, but they have to be amplified first - powerful enough to drive a speaker.

You can use an amplifier like a guitar amp.  If you only need to boost a headphone-like signal, you can use the amp built into the TV set.  Disconnect the built-in speaker and connect the Horizontal coil instead.  Find the wires to the volume knob - one of them is "from" the TV tuner.  Unhook that wire and connect it (and ground) to a connector on the outside of the TV.  Note:  sometimes "ground" is HOT and can shock the hell out of you.  Check first.  If it is, use a 1:1 transformer from Radio Shack between the knob and the connector.

[incapacitor]

I've got the tv to read it's own static by hooking up the speaker wires to the vert coil, but cannot figure out where to insert the music input wiring, presumably into the tv amp somehow. unfortunately, attaching wiring to the volume knob ground and the tv tuner yielded only a straight line [on the display]. what am I doing wrong?

[jerkey]

first, put the speaker back on so that you can hear what you're doing (unless you want to do this by watching the screen). There are three terminals on a potentiometer, such as a volume knob. More complicated volume knobs exist in stereo equipment, car stereos especially, but assuming your TV has a regular three-legged volume knob, here goes. One terminal will be connected to ground (it's not the middle one). The middle one goes to the audio amplifier and we'll leave it alone. The third terminal (opposite the ground one) is the signal coming from the TV tuner. The third terminal is the one you want. When you disconnect that wire from the knob, you will get a flatline (silence) instead of static. Now, connect an audio cable or connector to the potentiometer where it was formerly connected to the TV tuner signal. It must be at least loud enough to drive a pair of headphones. Now your signal is going into the volume knob - when you turn up the volume knob, it allows your signal to go to the amplifier. I hope this works!

[edwianni1]

Can this be done with a small portable 5" tv?

[Magnelectrostatic]

 If it is a cathode ray tube tv (big glass tube, not flat screen), technically it should be possible. I'm not sure if it would be worth it though. The wave is smaller than the screen, so a wave smaller than a 5" screen would be very tiny.

[edwianni1]

Thank you.

[Magnelectrostatic]

 No problem, and good luck.

[TobyBrock!]

I'm relatively certain I have it all hooked up correctly, but when I wire a power source to it, nothing happens. About how strong does the source need to be?

[Magnelectrostatic]

When you turn it on is there a horizontal line in the center of the screen? If not there's some sort of wiring problem.  Otherwise try a weak voltage, around 0.5 volts. I noticed that with a 1.5 volt battery the line would jump above the visible area so it looked like it wasn't working. 
Anything meant to power headphones should be weak enough to stay within the visible area, and strong enough to be visible.
If nothing works check everything or put some pictures up here and maybe I could take a look at them.

[TobyBrock!]

Actually, at this point, I blew the frame output. I'll need a new tv before trying this again. Oopsie!