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

[agis68]

maybe i missed on the text but this is only for audio waveform analysis or also for any purpose.....ie...to check a tv

[mgingerich]

Great instructable! I did this to an old black and white TV, and it came out pretty cool, except that for some reason instead of a full horizontal line showing up there is only a point or half-inch line that moves up and down in proportion to the input signal. Is there a way I can fix this?

[mgingerich]

I got it a little wider, but is there a way to make the wave use the whole horizontal length? It only moves in the middle third of the screen

[Magnelectrostatic]

Personally I'm not sure, but I think this instructable is jsut what you're looking for
http://www.instructables.com/id/Fully-Functional-Television-Oscilloscope/

[mgingerich]

Yeah, that's the sort of thing I want. After playing with my TV's settings for a while I realized the problem isn't easily fixed. Since the up and down dimensions are quite small, the signal from the vertical wires (intended for the vertical coil) that goes to the horizontal coil has too small an amplitude. I intend to substitute a sawtooth oscillator in place of the vertical wires instead.

[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.

[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

[Magnelectrostatic]

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.

[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!

[Magnelectrostatic]

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

[alex555155]

Could I just cut the wires instead of desolder?
I'm a noob at high voltage, and don't like desoldering.
Thanks!

[Magnelectrostatic]

You can!

[mysterion]

....tried this, turned on my tv it immediatly shorted out and turned off, reconnected the horizontal coil it worked.......tried it once more boom, some small capacitors started blowing :(

[Magnelectrostatic]

Aw man...that sucks. Sorry about the tv.

[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!

[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