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Electronics Repair (sci.electronics.repair) Discussion of repairing electronic equipment. Topics include requests for assistance, where to obtain servicing information and parts, techniques for diagnosis and repair, and annecdotes about success, failures and problems. |
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#1
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project: connect stereo audio out to monitor deflection yoke ?
I am trying to find an "artistic" use for a few old computer monitors
(one 9" monochrome and one 14" colour, both svga) that I have lying around, and am in need of suggestions from those with more experience of this. The idea is to perform one of the experiments listed towards the end of sam's Monitor FAQ, in the section on "turning a monitor into an oscilloscope". NO, I don't want to do that, but rather make an audio display, driving the yoke with a stereo amp to move the beam around the screen. However, before I disconnect anything from the yoke to attach the stereo, presumably I would have to connect some sort of dummy loads on the horizontal and/or vertical lines from the mainboard, as I don't want to risk running (and blowing up) the monitor with the yoke effectively disconnected from the scan circuits (wired to the stereo spkr outputs instead)? I would be interested to hear from anyone who has successfully hitched an audio source to the scan coils in this way. Or equally, someone who has been there, attempted that and found it a waste of time and effort! Any suggestions? regards, Ben |
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#3
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Interesting idea, but video monitors aren't designed to handle that sort of
thing. Your typical vertical deflection circuit is designed to work at 60 Hz, and the horizontal deflection circuit wants to run at 15.7 kHz (or even twice that frequency, if it's a VGA monitor). Going too far beyond those boundaries creates all kinds of hellacious noise, and/or fried components. It would probably be easier to use a cheap X/Y oscilloscope instead. They are designed to handle just about anything, and you can plug your stereo outputs directly into the 'scope inputs with no trouble at all. Any adjustments for optimum picture can be done right there from the front panel of the 'scope. |
#4
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"Matt J. McCullar" wrote in message om... Interesting idea, but video monitors aren't designed to handle that sort of thing. Your typical vertical deflection circuit is designed to work at 60 Hz, and the horizontal deflection circuit wants to run at 15.7 kHz (or even twice that frequency, if it's a VGA monitor). Going too far beyond those boundaries creates all kinds of hellacious noise, and/or fried components. It would probably be easier to use a cheap X/Y oscilloscope instead. They are designed to handle just about anything, and you can plug your stereo outputs directly into the 'scope inputs with no trouble at all. Any adjustments for optimum picture can be done right there from the front panel of the 'scope. or use a cheap PC with sound card and something like http://polly.phys.msu.su/~zeld/oscill.html |
#5
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Matt J. McCullar wrote:
Interesting idea, but video monitors aren't designed to handle that sort of thing. Your typical vertical deflection circuit is designed to work at 60 Hz, and the horizontal deflection circuit wants to run at 15.7 kHz (or even twice that frequency, if it's a VGA monitor). Going too far beyond those boundaries creates all kinds of hellacious noise, and/or fried components. It would probably be easier to use a cheap X/Y oscilloscope instead. They are designed to handle just about anything, and you can plug your stereo outputs directly into the 'scope inputs with no trouble at all. Any adjustments for optimum picture can be done right there from the front panel of the 'scope. Scopes (especially cheap ones) are generally electrostatic deflection, so have smaller screens. -- The e-mail address in our reply-to line is reversed in an attempt to minimize spam. Our true address is of the form . |
#6
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wrote in message ps.com... I am trying to find an "artistic" use for a few old computer monitors oscilloscope". NO, I don't want to do that, but rather make an audio display, driving the yoke with a stereo amp to move the beam around the You can't drive a yoke with audio and it makes no sense. You could just figure out the connections and hook the L and R to two of the color inputs but it'd be kind of crappy. I'd look for a circuit to do this from maybe Elektor or Silicon Chip (two magazines). -- N |
#7
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NSM wrote:
wrote in message ps.com... I am trying to find an "artistic" use for a few old computer monitors oscilloscope". NO, I don't want to do that, but rather make an audio display, driving the yoke with a stereo amp to move the beam around the You can't drive a yoke with audio and it makes no sense. Ever hear of Lissajous figures? You could just figure out the connections and hook the L and R to two of the color inputs but it'd be kind of crappy. I'd look for a circuit to do this from maybe Elektor or Silicon Chip (two magazines). -- The e-mail address in our reply-to line is reversed in an attempt to minimize spam. Our true address is of the form . |
#8
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wrote in message ps.com... I am trying to find an "artistic" use for a few old computer monitors (one 9" monochrome and one 14" colour, both svga) that I have lying around, and am in need of suggestions from those with more experience of this. The idea is to perform one of the experiments listed towards the end of sam's Monitor FAQ, in the section on "turning a monitor into an oscilloscope". NO, I don't want to do that, but rather make an audio display, driving the yoke with a stereo amp to move the beam around the screen. However, before I disconnect anything from the yoke to attach the stereo, presumably I would have to connect some sort of dummy loads on the horizontal and/or vertical lines from the mainboard, as I don't want to risk running (and blowing up) the monitor with the yoke effectively disconnected from the scan circuits (wired to the stereo spkr outputs instead)? I would be interested to hear from anyone who has successfully hitched an audio source to the scan coils in this way. Or equally, someone who has been there, attempted that and found it a waste of time and effort! Any suggestions? regards, Ben I did this years ago with an old 9" mono computer monitor, had to put an inductor where the horizontal yoke connected and a power resistor in series with the H yoke to match the impedance to what a stereo amp is expecting. It was entertaining for a little while but it got boring fast, as well as it burned a large hole in the phosphor in the middle of the screen, not that it mattered with all the burn that was already on it. |
#9
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"CJT" wrote in message ... Ever hear of Lissajous figures? Yup. And you can't drive a yoke with an 8 ohm speaker output. It takes some serious amps. And you can't vary the frequency by very much either. -- N |
#10
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On Fri, 04 Feb 2005 05:34:29 GMT "NSM" wrote in Message
id: FPDMd.303$rB6.170@edtnps91: "CJT" wrote in message ... Ever hear of Lissajous figures? Yup. And you can't drive a yoke with an 8 ohm speaker output. It takes some serious amps. And you can't vary the frequency by very much either. FWIW, I did exactly that about 20 years ago on a color RCA tube chassis that had a deflection problem. Disconnected the yoke from the chassis and used the left channel to drive the horizontal and the right channel to drive the vertical. The patterns would fill the screen at about 3/4 volume using a 50W per channel receiver. It was quite the hit at parties. |
#11
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Thanks for the responses.
Seems like the older sets were far more forgiving when it comes to disconnecting the yoke. I have already tried using the vertical of the 9" mono monitor, which produced a result, but as JW posted, you need a fair bit of volume to do it. I haven't yet tried the horizontal. Will look at the option of an inductor and series load. and also look out for the magazine circuits NSM suggested for the colour.- will post with results at a later stage! regards, Ben |
#12
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#13
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wrote in message ups.com... Thanks for the responses. Seems like the older sets were far more forgiving when it comes to disconnecting the yoke. I have already tried using the vertical of the 9" mono monitor, which produced a result, but as JW posted, you need a fair bit of volume to do it. I haven't yet tried the horizontal. Will look at the option of an inductor and series load. and also look out for the magazine circuits NSM suggested for the colour.- will post with results at a later stage! I recall the Radio Shack Color Computer had an optional ROMPak which did various displays like those in Media Player software when you hooked it up to your stereo. They even claimed you could tune your room with it - a bit dubious I think. -- N |
#14
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NSM wrote:
"CJT" wrote in message ... Ever hear of Lissajous figures? Yup. And you can't drive a yoke with an 8 ohm speaker output. It takes some serious amps. And you can't vary the frequency by very much either. That's going to depend on the specifics. I agree that an audio amp might not be ideal. But the other poster says he did it, and I believe him. -- The e-mail address in our reply-to line is reversed in an attempt to minimize spam. Our true address is of the form . |
#15
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Ol' Duffer wrote:
In article , says... We burned the phosphor mid-CRT pretty badly, but the TV was a throwaway anyway, so it didn't matter. You could detect the incoming signals and feed them to the CRT board to modulate beam intensity. Yes, I played around with that a bit, but the desired intensity is a function of beam X-Y velocity, and at the time it was easier to just let it burn. BTW, I'm not convinced a regular stereo amp is suitable to drive a yoke. At least not without some extra work. Yoke windings are predominately inductive and intended to be current driven (implying high impedance source), while stero amps are designed to be low impedance voltage sources driving mostly resistive loads. Add to that the fact that the two windings are usually optimized for different signal voltage levels (12~40 Volts vertical and 100~300 Volts horizontal ballpark). You could try 70 Volt PA speaker transformers with series resistors to match/step up the amp to yoke. -- The e-mail address in our reply-to line is reversed in an attempt to minimize spam. Our true address is of the form . |
#16
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You'll need a spare yoke and stepup transformers to match impedance. Set the
original yoke aside still hooked up and put the spare on the tube. To use a computer monitor you may need to have an old PC just to get it to turn on. In fact, to set the purity you'll need to feed the monitor all one color from a PC, then you can interrupt the video signal and start playing around with that too, use a low value cap fo example to feed the high frequencies to modulate the beams. (yes, as you suspect I have done it, on an old 21" round color TV) Have fun. JURB |
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