TV Oscilloscope

Need an oscilloscope? Want to see the music? Don’t have money, but do have a old TV? Then this TV to oscilloscope mod may be right up your alley. Now don’t go running off just yet, when you’re working inside of a CRT device you are exposed to mains current, high voltage, and high frequency, so extra care needs to be observed .

If you have your rubber welding gloves, and have discharged all your fat capacitors (including the CRT) its pretty much the same magic trick as couple we have previously featured. Patch an amplified input signal into the vertical deflection coil and let her go, but this instructable features much more detailed instruction, and photos so you have a much better chance of replicating this (not quite lab grade) potentially useful device.

Join us after the break for a short video.


25 thoughts on “TV Oscilloscope

  1. I wouldn’t count on using your TV again after this… the fact that you’re condensing the entire raster in to a few mm wide line means it’ll exaust the phosphors VERY quickly if you leave it as a static image for too long.

    1. Putting the electromagnet on the computer is perfectly safe. It’s only an input, like a microphone. If you applied power to the coil, you would probably damage something, but as a sensor it’s fine.

  2. @deltron
    i can put what appears to be a gun to my head and pull the trigger that does not mean id die
    coils of wire only emit electromagnetic radiation when charged with a current and even if it was i doubt magnetism would effect a laptop at least at that size

    its simply an EMF detecting coil

    if your scope sends power down the leads i think its time to get a new scope

    but anywho yeah i have wanted to put a sawtooth occ in to one of my many junk TVs and make a little scope for projects that i dont want to get my digital scope within a mile of XD

  3. My friends and I used to do this with junk TVs back in the late 90s… We would tie the X and Y magnets to left/right off a stereo amp then tinker with the pots on the neckboard to get it a color we liked.

    There was a particular sequence off of Nine Inch Nails’ “Further Down the Spiral” that was quite interesting– it was essentially a short sample being looped, but the loop window was being shortened (and possible moved along the length of the sample, I cannot remember).

    Toward the end of the sequence the waveform eventually stabilizes to a figure on the display before undulating back out into a normal star shaped display.

  4. @fartface: The input runs through an adjustable amplifier to scale the display. All that’s missing is some calibration (function generator) and a scale on the screen (silver Sharpie).

  5. cool hack, but it’s bee done a million times. not sure if he mentioned it, since I didn’t read through it yet, but you can kill yourself on an unplugged CRT tv/monitor even if it’s unplugged.

  6. Since when does a hack HAVE to be something new to be accepted and not get slammed? No, it’s not an oscilloscope. Wow, thanks for that valuable piece of information Fartface!! The name says it all! :)
    I think it’s pretty cool when people re purpose electronics. Nice hack. :)

  7. Even with a trigger, it is still pretty useless, because the electromagnetic deflection in the TV is much slower than electrostatic deflection in CROs, (self inductance of the coils prevent fast changes of the magnetic fieled)

  8. Yeah I tried this; even made a variable sawtooth oscilator for the sweep and an amplifier/attenuator for the signal. It sucked. Then I tried one of those little lcd didital deals f that. In the end $50 (incl. shipping) snagged me a dual trace sencore from the ‘nam era. wish I would’ve done that in the first place.

  9. @fartface
    scopes did not start displaying frequency and voltage until what … the early 80s?
    and an oscope is defined “a type of electronic test instrument that allows signal voltages to be viewed, usually as a two-dimensional graph of one or more electrical potential differences (vertical axis) plotted as a function of time or of some other voltage”
    so if your to lazy to calculate your own voltage or frequency buy a professional scope and stop complaining when a $30 scope does not have the features of a $400 scope

    god this new generation of hackers are so damn lazy sometimes …

  10. @VintagePC While true, you can also easily just turn down the G2 control, usually located on the flyback itself, or on much older/larger models somewhere along the hv line there’s a splitter with a knob to turn it down.
    I know a lot of Mitsubishis has a vertical protect circuit that automatically cut or dimmed the screen if the vertical collapsed (due to vert amp failure, caused by dried/leaky cap in the v-amp circuit) just for this reason (the entirety of the screen focused into a fine center line)

  11. @ everyone who has said it’s been done before…


    Maybe he used a new technique someone never saw before, or somehow inspired a thought that others had yet to experience. The amount of negative comments is pathetic and shows how sad and bitter you all are.

    While this is nothing entirely new, I do not see any hacks posted by anyone who is talking smack against his contribution. Negative comments on Hack-a-Day are counteractive. I dont mean critical comments that can help along a project, but the “dood teh haxor is stoopid” comments.
    If even one person is turned off to hacking due to a pointless negative comment, then we all lose.

    Get over yourselves and submit something to inspire others. If you want to troll, go back to


    Neat execution. Great choice of music too.

  12. It’s a cool hack but it sounds like somebody hasn’t welded before…. or worked on a tv before for that matter. (who wears rubber gloves when working on either of those?)

    The only thing you have to be worried about when working on old televisions is if you’re gonna pull off the HV line from the flyback and you recently ran the set, make sure you stick a screwdriver beneath the nipple and touch it to ground to discharge it before you go grabbing at it.

  13. I did it in 1970. High school 1’st prize in tech-art fair.
    Is it too late to glom onto a vector game monitor. They are linear to a few meg.
    The danger in late-model tube TVs is the hot chassis design, often 60v; with plug in either way.

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