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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.
Hi ..?<br>This is the third TV burnt !! ?<br>It was showing that line and then after 7 minutes suddenly disappear! it is happening every time<br>Why that does not work with me?<br>The TV is working but the screen is black.<br>The horizontal coil supposed to handle the 60hz what is the wrong ?<br>I even could not try that circuit you suggested ...
Try connecting a &quot;dummy&quot; coil to the disconnected output. Try to choose a coil of similar impedance to the yoke. (1-2mH, 5-10 ohms).<br><br>Next time try using a small black and white unit. The simpler the better.
<p>Sorry I took so long to respond! And I'm sorry about all the TVs; that's too bad.</p><p>The TVs don't work at all any more? And does anything actually burn? Do any components inside look like they failed?</p><p>Moving the deflection coils shouldn't make anything change in a way that would break the TV</p>
no problem<br>actually I finally did it! and I find out what was the problem<br>thank you very much for your help :) and your instructions.<br>
<p>Woohoo! I'm glad to hear that.</p>
<p>I am not surprised people are killing TV's. It is not uncommon for Large, color displays to have protection circuitry that shuts the system down in the event of a deflection coil failiure. When these things were new they were very costly and vulnerable to permanent damage from burn-in. Any one this worked well for no doubt noticed how intense the trace is at normal brightness. Normally that beam scans the whole frame. My advice is to find yourself a small black and white crt to work with. Early Macintosh computers (SE, Plus, SE/30, etc) are excellent for this. Very rugged. <br><br>As for the input, direct feeding the vertical yoke is awfully crude. In order for this to behave anything like a real scope from the signal's point of view, you need a buffer, an amplifier, and an impedance matching network. Otherwise referred to as the scope's vertical amplifier. If you don't know what that means or how to put that sort of thing together, if the TV you're working with has an audio input, I would recommend finding the wires leading to the TV's speaker, sending them to the vertical yoke, and putting your signal through the audio input. If you're using a monitor or sound is no good, you could also use any old stereo power amp that can drive low impedance speakers.</p>
<p>I used jerkey's suggestions and just rotated the coils and hooked the old horizontal coil to the speaker lines. This is intended for a brain-in-a-jar project so random wave patterns is just fine. </p><ul><li></ul>
Sounds like a neat project!
Hi<br>I do all the instruction for 3 tv !!!<br><br>One of them dosnt work anymore <br>and the rest show that the herizontal line but when I contacted to the signal sources still show me that line<br><br>There is no wave shape. :(<br>
<p>What type of signal source did you use? It's possible that it wasn't strong enough. A good source to test with is a battery connected to a potentiometer. You can put the center pin of the potentiometer on one end of the vertical coil and ground the other, then you should be able to move the line up and down.</p>
First I want to thank you<br><br>I am sorry if I am gonna bothering you<br>I want asking you <br>I don't think I get it !<br><br>I connected with my laptop and then my phone and I played some video on YouTube that had 20~3000 Hz <br>Is not enough ???<br><br>And you are suggest that I should to connect the v-coil with battery and potentometer just like that without a laptop ???<br><br><br>
<p>Not a bother at all! Your laptop or phone should work fine, was the volume turned up high?</p><p>And yes, no laptop. I've attached a crude image of the setup.</p>
<p>oh !!</p><p>thank you sooo much !!</p><p>I will try that and tell you what I got (:</p>
<p>Good luck! Hopefully we can figure this out.</p>
Hi...<br>It is me agin :)<br><br>It is ok if I choose a 9 volt battery ?<br>And what would you suggest for the pot ?<br> 1 kohm good ?
<p>Both of those should work, but you might want an additional resistor of 100 to 1000 ohms in series with the battery to limit its current. You can also just limit it by how far you turn the pot.</p><p>Now, this reply is getting a bit longer than I had hoped...but I think on my TV the vertical range was only about a volt, if even that, so I imagine a AA (or AAA or D) battery would also work fine, and with the 9V battery you might only have a small range on the pot that's visible on the screen. If the voltage goes too high or too low (negative) the line will disappear completely!</p><p>I'm also not sure what the resistance is in the coils (if you have an ohmmeter you can always measure it!) and I'm not sure how much current they can handle, which is why I recommended the additional resistor - to prevent the battery's full voltage from falling directly across the coil.</p>
<p>I got an old CRT monitor can I use for above</p><p>which wire is best to extend the coil wires out of the cabin like any suggesions to use a Monitor cable etc.</p><p>Frequency limitations of this CRT oscilloscope</p>
<p>Any wire should work; it does not have to be something special.</p><p>The frequency limitations are vertical scan rate and the width, because we use the vertical coil-driver to drive the horizontal coil, and the width determines how much information we can get in each scan across the screen. We can measure the width as vertical bars, and effectively the number of bars multiplied by the scan rate is the sampling frequency. The highest frequency this will work for is less than half of the sampling frequency.</p><p>From this wikipedia article, <a href="https://en.wikipedia.org/wiki/Refresh_rate"> https://en.wikipedia.org/wiki/Refresh_rate </a> a 1280 x 1024 TV would have a vertical scan rate of 89 Hz; admittedly, I do not know the resolution of my TV. Assuming is it 1280 x 1024 though, the middle portion that gets used is probably 1/3rd of the total width, or 1280/3 = 426.6 lines. Let's say, 427.<br></p><p>So the frequency limit is</p><p>(427 lines per scan) * (89 scans per second) / 2 = 19,001.5 Hz</p><p>I've never looked into this before, and I'm actually shocked. That's really cool! The upper limit of human hearing is near 20 kHz, so this covers just about everything you would find in music. At 19 kHz though, a sine wave would look more like a very thick vertical line. Still though, pretty neat!</p>
I used an auxillary cable that my teacher found me. it was old enough.
<p>Great! I'm glad it worked out</p>
<p>Hey, I really want to make this but all the headphones I've cut apart are too new! Could you let me know what kind of jack to buy? Thanks.</p>
<p>What do you mean? What headphones do you have?</p>
The headphones that I use have tons of tiny coloured wires within them, not the three wires described.
<p>Are they by any chance those Nokia earphones with the big (wide) black connector?</p>
<p>I'm with yonatan24 on this one, I've never seen headphones that wouldn't work for this. It should be possible with any pair (especially a cheap one that you don't mind destroying). At the same time, if you want to buy the parts for it you could get a male audio jack and attach that to the TVs input.<br>(for example, this 3.5 mm audio jack <a href="http://www.mouser.com/ProductDetail/Switchcraft/35HDNN/?qs=MI16PYk8XEP5m3KuUk%252bt5g%3D%3D&gclid=CO-z8Jjs1MoCFYeRHwod8DYEdg">http://www.mouser.com/ProductDetail/Switchcraft/35...</a><br>not that you would have to buy from that supplier - just as an example)</p>
<p>Hi, I've added your project to the <em style="">&quot;</em><em style="">Make Your Own Oscilloscope!</em><em style="">&quot;</em> Collection</p><p>This is the link If you are interested:</p><p><a href="http://www.instructables.com/id/Make-Your-Own-Oscilloscope/">http://www.instructables.com/id/Make-Your-Own-Osci...</a></p>
<p>Neat! Thank you</p>
<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>
<p>I'm sorry for this incredibly late response, and even more so because I don't have an answer. That's pretty interesting though. Mine would only display on a small rectangle in the middle of the screen, which I assumed is because the vertical coil wasn't meant to deflect the beam as much as the horizontal coil, but in your case that doesn't quite seem right because the beam isn't symmetric. It's like the right side of the screen is being swept over or refreshed too quickly. Even if that is the case though, I'm not sure what would cause it. </p><p>But if this project is still sitting out and you happen to have some magnets around, you might be able to deflect the beam away from that edge, and worst case magnets and CRTs always gets interesting! Let me know if you figure it out</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>

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