Dissecting a cathode ray tube television

In summary, an old color cathode ray tube television could be dangerous if you don't know what you're doing. It could contain large capacitors that could shock you, and there is no safe ground in these sets.
  • #1
stickythighs
37
0
I'm considering dissecting an old, color cathode ray tube television. Do cathode ray tube televisions have capicitors in them that could shock me?
 
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  • #2
Please do not play around with electronics if you don't know what you're doing. I'm not going to give you any information regarding TVs because that is not a safe place for an amateur to start.
 
  • #3
Not to mention the large evacuated glass thingie the picture appears on... a very dangerous thing even when the tv is switched off & disconnected from the mains.
 
  • #4
zeitghost said:
Not to mention the large evacuated glass thingie the picture appears on... a very dangerous thing even when the tv is switched off & disconnected from the mains.

Why would the glass screen of a tv be dangerous even when the tv is switch off and disconnected? Do you think it would be dangerous because it could break and cut someone?
 
  • #5
turbo-1 said:
Please do not play around with electronics if you don't know what you're doing. I'm not going to give you any information regarding TVs because that is not a safe place for an amateur to start.

What is a safe place for an amateur to start?
 
  • #6
stickythighs said:
What is a safe place for an amateur to start?
Start with battery-powered circuits that you can bread-board. Radio Shack has bread-board kits with components that you can learn from. Learn the functions of the components, how to read the values of those components from markings, how to measure the values using a digital multimeter, etc, etc. Before you delve into AC or high-voltage DC circuits, you MUST learn how to test and safely discharge capacitors. They can kill you.
 
  • #7
Turbo,

What does bread board mean?
 
  • #8
A bread-board is a perforated plastic circuit board on which you can build circuits using discrete components.
 
  • #9
stickythighs said:
Why would the glass screen of a tv be dangerous even when the tv is switch off and disconnected? Do you think it would be dangerous because it could break and cut someone?

There is a vacuum inside the tube, so it could implode and send glass shards flying everywhere. Also there may be toxic chemicals.
 
  • #10
In the tv show MacGyver, MacGyver once made a bomb out of the cathode ray tube of a tv, and that's what sparked my interest.
 
  • #11
The capacitors in a crt are large enough to kill you and they can keep a charge for years after being plugged in.
 
  • #12
stickythighs said:
In the tv show MacGyver, MacGyver once made a bomb out of the cathode ray tube of a tv, and that's what sparked my interest.

Well there's a healthy interest in learning... :rolleyes:

As others have said, please learn a LOT more before messing around with a TV or computer monitor. In addition to the large mechanical energy stored in the evacuated CRT itself, the high voltage circuit that charges up the CRT (the conductive coating on the faceplate is held at around +25kV with respect to the electron gun in the back/neck of the CRT), can hold a residual voltage of several kV when turned off. And that residual charge sticks around for an amazingly long time in some cases. Certainly several days (probably not years though).

There are also AC mains capacitors like after the input bridge rectifier, which can stay charged up to hundreds of volts for days as they leak down. Very unpleasant when brushing up against exposed leads (Quiz Question -- why do I know that? Ouch.).

Finally, there is no safe "ground" in television sets. They often use a "hot chassis" design, which means that if you do not use an isolation transformer in working with open TVs, you will either blow up your oscilloscope or electrocute yourself. Or both (now THAT would be a bad day, to have both happen...).

So a) start with more basic circuits to learn from, and b) don't make your learning aimed mostly at how to blow stuff up.
 
  • #13
stickythighs said:
Why would the glass screen of a tv be dangerous even when the tv is switch off and disconnected? Do you think it would be dangerous because it could break and cut someone?

Because they still retain a charge, and pack quite a punch even when unplugged, don't do it.
 
  • #14
There is a lot of chemicals inside a CRT, such as lead and phosphorous in form of a fine powder which if disturbed will disperse into the air.
 
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  • #15
stickythighs said:
I'm considering dissecting an old, color cathode ray tube television. Do cathode ray tube televisions have capicitors in them that could shock me?
You could get some damage playing with something like that, but you can also discharge capacitors with a resistor (~50-200k Ohmms value should be fine) connected to two wires.
 
  • #16
Most new CRT circuits and power supplies have built in bleeder circuits which discharge the voltage fairly quickly.
As long as the bleeder circuits themselves are not broken which happens from time to time.

Older CRT implementations could hold a significant charge for months.
 
  • #17
DON'T DO IT! EXTREMELY DANGEROUS!

I have seen dangerous charges on CRT's that have been disconnected for a couple years.

Just don't do it.
 
  • #18
stickythighs said:
I'm considering dissecting an old, color cathode ray tube television. Do cathode ray tube televisions have capicitors in them that could shock me?

Heck, yeah they do! Experienced repairmen usually won't even touch one until it's been sitting unplugged for a week or more. There can definitely be enough charge in TV capacitors to kill you.
 

1. What is a cathode ray tube television?

A cathode ray tube television, or CRT TV, is a type of television that uses a cathode ray tube to display images. It was the most common type of TV until the rise of flat screen TVs.

2. How does a cathode ray tube television work?

In a cathode ray tube television, an electron beam is produced by a cathode and directed towards a phosphor-coated screen. The beam is then controlled by electromagnets to create images on the screen.

3. What are the components of a cathode ray tube television?

The main components of a cathode ray tube television include the cathode, electron gun, deflection coils, phosphor-coated screen, and electron beam control circuits.

4. Why are cathode ray tube televisions not as common anymore?

Cathode ray tube televisions have been largely replaced by flat screen TVs due to their bulky size and high energy consumption. Flat screen TVs also offer better picture quality.

5. Are there any risks associated with dissecting a cathode ray tube television?

Yes, there can be risks involved with dissecting a cathode ray tube television, such as exposure to high voltage and potential release of toxic substances, such as lead and mercury. It is important to take proper safety precautions and dispose of the components properly.

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