Print PDF
Favorite
Email
There are a few Instructables and otherwise internet based instructions on how to modify a television set into an audio visualizer or other simple oscilloscope-like device. This Instructable will show you how to create an actual lab oscilloscope worthy of a poor, amateur electronics enthusiast. The final product has optional audio output, variable input voltage from millivolts to hundreds of volts, as well as manual horizontal frequency locking. The total cost for this project was around $20.
To give proper credit, this Instructable is an improvement on Magnelectrostatic's at http://www.instructables.com/id/How-To-Make-A-CRT-TV-Into-an-Oscilloscope/. I wouldn't have been able to complete my mod without it. Thanks!
UPDATE (12-28-10):
This mod is not capable of displaying much outside the human audible range (20-20k Hz).
Also, since TVs are highly variable in design, this Instructable is intended for people who can do their own experimenting. This of course requires experience in electronics. Your TV will probably be different from mine. My instructions may not apply to what you're working with. They're guidelines. I hope they help you modify your available resources by providing ONE particular example.
To give proper credit, this Instructable is an improvement on Magnelectrostatic's at http://www.instructables.com/id/How-To-Make-A-CRT-TV-Into-an-Oscilloscope/. I wouldn't have been able to complete my mod without it. Thanks!
UPDATE (12-28-10):
This mod is not capable of displaying much outside the human audible range (20-20k Hz).
Also, since TVs are highly variable in design, this Instructable is intended for people who can do their own experimenting. This of course requires experience in electronics. Your TV will probably be different from mine. My instructions may not apply to what you're working with. They're guidelines. I hope they help you modify your available resources by providing ONE particular example.
Remove these ads by
Signing UpStep 1Safety
This project involves working in close proximity to the television's exposed flyback transformer and high voltage capacitors, which are both potentially lethal devices if you do not take proper safety precautions.
First, the obvious step: Is it plugged in? Unplug it! Isn't it funny that this is the exact opposite of what a tech normally tells you...
When you remove the shroud, be careful not to rip any wires from the circuit board, and do not touch any of the exposed contacts. Identify large capacitors and take note of their voltage ratings. 50v and above are especially dangerous, and should be discharged with a well insulated screwdriver across the contacts prior to tinkering if possible.
UPDATE (12-28-10):
Ok, ok, I generally dislike disclaimers because they are almost never legally sound. But for those of you who don't get the idea from the above paragraphs...
Don't attempt this unless:
you have a solid grasp of high voltage safety practices.
you have a solid grasp of electronic equipment in general.
you have someone around to call 911 or give you CPR.
you have experience working with mains (120VAC) power.
you are not a moron.
I take no responsibility for damage to your health or equipment. All damages incurred are the sole responsibility of the end user.
First, the obvious step: Is it plugged in? Unplug it! Isn't it funny that this is the exact opposite of what a tech normally tells you...
When you remove the shroud, be careful not to rip any wires from the circuit board, and do not touch any of the exposed contacts. Identify large capacitors and take note of their voltage ratings. 50v and above are especially dangerous, and should be discharged with a well insulated screwdriver across the contacts prior to tinkering if possible.
UPDATE (12-28-10):
Ok, ok, I generally dislike disclaimers because they are almost never legally sound. But for those of you who don't get the idea from the above paragraphs...
Don't attempt this unless:
you have a solid grasp of high voltage safety practices.
you have a solid grasp of electronic equipment in general.
you have someone around to call 911 or give you CPR.
you have experience working with mains (120VAC) power.
you are not a moron.
I take no responsibility for damage to your health or equipment. All damages incurred are the sole responsibility of the end user.
| « Previous Step | Download PDFView All Steps | Next Step » |
Brofist!
The Vertical coil is usually driven at about 80-130 volts peak.
You should be aware, that the Horizontal coil is wired in parallel with the flyback transformer, and the high voltage will change when removing the coil from the circuit, raising or lowering the high voltage (usually the latter)
The highest voltage you'll find in a TV set is the EHT Flyback connected to the picture tube via the thick cable in a suction cup looking thingy. On a B/W set you'll have approximatelt 10 Kv (Kilovolt) on this, and on a Color monitor Approx. 25 Kv.
I have done this mod a couple of times, and have replaced the Horizontal coil with an other inductor to keep the circuit working correctly. Around 400 uH of inductance should do it.
I added a Schematic cutout showing the Horizontal coil connected across the Flyback.
now the questions for you both, I have a 5.5" black and white plustron TV/FM radio that runs on 12V, Same kinda thing as used here, single channel that needs to be tuned each time.
The wires from the board to the coils are labled H1/H2 and V1/V2, that saves a bit of work but now I am wondering about the amp ciruit, is there anyway to make it run on 12V, it would be really nice to have the whole thing on 12V to save on transformers and also run it from a battery if needed.
I will of course be doing model specific instructable, Aeternusjunk, would you mind if I used this build as a foundatio, use the odd paragraph here and there?
Great work dude!
The main problem with a 12v power supply is the op-amp used in the amp circuit. Everything else will be fine, but the TL082 requires a minimum of +/-7v to operate properly. This means you'd need at least a 14v battery to run the amp. So close, yet so far. It might still work, so test it! However, there are low voltage op-amps such as this one that would be a good replacement. Basically you are looking for a 2 channel, through hole, dip-8, +/-6v supply (or lower) op-amp. Anything that fits that description should work. If you're running things from a battery, just chop off the AC rectifier section and you're gold. This is everything before and including the 4 diodes, but I recommend keeping the filter capacitor.
Wouldn't this let you choose the frequency, giving a lot more flexibility and make it more useful?
Or is that just so complicated that it isn't worth it?
The other problem, as I'm now realizing (or re-realizing) is that any signal of high enough frequency to warrant preserving the high horizontal scanning frequency will itself be very high frequency, subject to the impedance of the vertical deflection coil. You would need a another independent flyback transformer just for your input signal. This sounds like a lot of work to me.
I think I'm going to need to severely modify some things, considering the ancient monitor I want to use dosen't have a full image displayed.
Ill let you know what happens.
If it makes a difference, it's a 5.5 inch b/w portable tv...
Thanks!
stiiiiiiiiiiiill
Also, when I turn the TV on, the horizontal line doesn't cover the entire length of the TV. Instead, it fluctuates around 3/4 of covering the whole screen, without ever touching the edges. Is that normal?
To hook up an audio source, identify the vertical deflection coil and make ABSOLUTELY SURE it's not electrified with a voltmeter or other tester. For an iPod, you'll need a 1/8" audio plug for the iPod, then strip the other end of the cord. The inner cores are the strereo signal. The outer exposed strands are the common ground, but your wire may be different, so experiment. As long as the coil isn't electrified your ipod is relatively safe.
I have taken apart an arcade cabinet, completely disaassembled, and put it back together, which includes handling the cathode tube monitor. This web page goes into detail on how to discharge the monitor:
http://www.stickycarpet.com/pinx/md.html
I used jumper cables and a large screw driver.
It is important that this step is done, because even a monitor that has been unplugged for a while can still carry a lethal charge. It is very important that people understand this before messing around with monitors such as these. It is very dangerous.
Once the cathode tube and all capacitors are discharged, it is generally safe to handle, but do research before you mess around with these.
FYI: You can pick up these older tvs for a few bucks at the local goodwill stores, I might just go visit one this week.
This is a nice idea but.......Someone is going to die copying this.
If you insist on suicide, here are a few pointers...
1) make sure someone else is close-by. They can call for help. It's no good if the neighbours call the police 3 weeks later because of the smell.....
2) stay away from the live mains part.
3) and the rubber sucker on the tube
4) and the focus control (from the flyback transformer to the tube neck)
5) choose a portable tv. operate it from 12v if you can.
6) choose a tv with a SCART socket - the main chassis should be isolated from mains.
7) be careful! - if you don't know exactly what you're doing then ask someone who really knows!
Focus volts 5-7 KV really hurts and gives a burn too - been there done it. 25KV throws you across the room - been there, done it. you also shake and have a cold sweat. swearing is also normal.
Mains electricity will kill if it gets the chance. I've done silly things but been lucky. You may not be!
I take it as a compliment for the author to say this.
I love your new disclaimers/warnings!, well done. Some people DO need to be warned!
In the UK Analog(ue) TV has been switched off and MANY small portable sets are junked. There are some beautiful cheap 6 inch screen portables that are nice to modify. They are based upon a 28-pin chip (5150 I think) the datasheet is available. I have modified 3 for video-input to use as cctv monitors.
An ideal candidate to play with!
Cheers,
Andrew
Thanks