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.

-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.
<p>great instructable. I just completed this on a 1988 Cosmo Communications 5&quot; portable color TV. My only issue is that the right half of the signal image is out of focus! I've tried every adjustment save the ring tabs on the neck of the tube which are glued together.... Any ideas? Short clip attached showing the problem!</p>
Is there a way I can make it display a single transverse wave and not multiple... well whatever those waves are called. I don't want to settle for less and I really want to make this oscilloscope. If it's another circuit I can do with that. I know it's been three years since you last answered a question but can you help me out?
Thanks that helps a lot! I'll check out the video. And I was reading the first top comment and it said 3 years so I thought that would be the most recent one. Thanks again!
<p>There's a response from ten months ago if you look further down! But I am pretty sporadic with response times...<br>So if I understand correctly, the problem with this is that there will be multiple waves visible on the screen at once?<br>I think it's related to the refresh rate of the screen - the electron beam moves across the screen at some finite rate, over and over again. Say that we put in an audio signal thats a higher frequency than the beam's frequency; now the beam wants to move up and down faster than it moves sideways, so it starts drawing weird looking stuff. This guy made a scope the same way, http://www.youtube.com/watch?v=8kupA_gp3EE , and gets some really nice looking - low frequency waves at the beginning.</p><p>But that could also be completely wrong! Maybe the old waves haven't faded out by the time the next one is drawn on, which would be a property of the phosphor coating on the screen. Or maybe something else! If you have any more questions let me know, and good luck!</p>
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.
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.<br>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).<br>Hope this helps.
<p>Series resistors might help with more volts in the input signal. If the signal is clipping, add any one of following resistor, 10, 100, 1k, or 10k, ohms in series with the coil. </p>
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).<br><br>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.
Hello, nice instructable!<br>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.<br>How do i do that?
I'm really not sure....don't even know what that means actually, sorry I can't be more help.
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
I never thought of that. I tried hooking the sound input directly to the vertical coil and the distortion was awful. <br>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). <br>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.
<p>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.</p><p>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. </p>
OK so I killed the TV in process lol. <br />Then I got a Mac classic with a bad logic board. <br />In process broke its vertical sweep generator somehow <br />So now ended up with this: <br />http://www.youtube.com/watch?v=ye3nyxc_MOw <br />http://www.youtube.com/watch?v=F0i6A2QjdBw <br /> <br />This was before the generator died: <br />http://www.youtube.com/watch?v=Fn_st_sX9fw <br /> <br />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. <br />Thanks for the i'ble!
So THAT's an xy scope! It looks great!
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. <br />I'll give it a try soon and post the result
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?
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
Personally I'm not sure, but I think this instructable is jsut what you're looking for<br>http://www.instructables.com/id/Fully-Functional-Television-Oscilloscope/
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.
<p>Alternately you could try rotating the coil 90 degrees on the CRT and reattach the original vertical feed, now serving as your horizontal feed, to the original vertical coil, now serving as your horizontal coil. Original being that which was before you made any changes. With the original vertical feed feeding the original vertical deflection coils, the feed is likely to drive the most power coil. Then you can adjust the original vertical potentiometer, now horizontal after rotating the coils, so that it further deflects the beam. </p>
<p>Many CRT's have potentiometers that you can adjust for the vertical and horizontal. Your old vertical is now your horizontal. If your lucky, yours might be labeled. I strongly suggest using a plastic screw driver when tweaking these. </p>
<p>This works great! Just don't expect your ipod or other small MP3 player to survive it. With the CRT monitor I used somehow I got some voltage coming back through the audio wire. I may have overlooked something but I don't think so. Great instructable though!</p>
<p>So ive found the 2 vertical coil and cut the wires to get the horizontal line, but when i connect the 2 hozirontal wire to the 2 vertical wire from circuit, i get a small line like in the picture, but its burry and messy, if i plug them back to how they were, i get the long and bright horizontal line back, so i was wondering if i could just cut the 2 vertical wire and plug them to the amplifier instead of doing anything else?</p>
<p>how to convert soket from 7 pin to osissiclope</p>
<p>Hey, I just tried this with my friend, and it works, but we used an old emachines CRT moniter. As soon as we tried it for a little bit we smelled something burnning, when we messed with the wires to make sure they where secure we tried it again and got the same burnning smell. Not really sure what to do? Any sugestions on what it might be or maybe where it might have burned?</p>
Have you tried it with the case open (be careful if you do!) to see if there's anything visibly burning?<br>And I'm guessing it happens without the audio attached? That source should have enough power to damage anything, so maybe the horizontal coil can't handle the power from the vertical supply. If you have an infrared thermometer (one of the non-contact ones) you could try measuring the temperature of the coil while it's running (and remember, don't touch anything!)
<p>something to control the wave width would be handy, I imagine someone who knows something about how those coils change the beam (ie not me) could rig up a simple arduino circut to control it, just for when you have a situation where instead of looking out sound, you are looking into the mhz spectrum.</p>
This is a very informative instructable. In the morning I plan to experiment with both axis's with a different song on each coil and a goodtimes dvd playing in the combo tv.
so I tried this, and I got to the point where I switch the wires but when I plugged in my ipod I got only a fast clicking noise, so I reconnected everything to normal and the clicking noise persisted. any suggestions?
Is it an audible clicking noise? <br>And it comes from the tv even now that you've placed things back the way they originally were?
maybe i missed on the text but this is only for audio waveform analysis or also for any purpose.....ie...to check a tv
Could I just cut the wires instead of desolder? <br>I'm a noob at high voltage, and don't like desoldering. <br>Thanks!
You can!
....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 :(
Aw man...that sucks. Sorry about the tv.
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.<br>
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?
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). <br>So it's definitely possible, it's just a matter of how....<br>Awesome idea by the way.
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
Interesting...are you sure you only touched the part of the circuit board where the coils are attached?
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
Weird, if you ever figure it out make sure to comment!
A speaker is just a coil of wire but that never broke anything...
it's great to turn the knobs to VoltDIV and timeDIV :)
how can i tell polarity or does it not matter
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.
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:<br>
can you make an instructable please, i have one too and would like to know how you did it.
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.

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Bio: An electrical engineer who likes to make things.
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