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Old Tube tvs?

  1. Feb 17, 2012 #1
    First you will have to forgive me for being uneducated in this area.

    I have an old record/tv console I bought with plans of upgrading it with a flat screen tv.
    When I brought it in my house the back of the tv was damaged and the piece of the tube tv was exposed. None of the glass was broken but it is like the seal was broken. And now it is making kind of a hissin noise inside of the tv. Im not sure what happened. Are there any gases coming out of it that are toxic? The spot that was damaged looks like the bottom of a light bulb where it meets the metal threaded part. So if you pull a light bulb out of something that it is screwed to tight into and you only get the glass part out that is basically what happened with the back of the tv. What should I do. Anything toxic leaking or am I being too worried?
     
  2. jcsd
  3. Feb 17, 2012 #2
    Inside the tube there is a vacuum in other words the air has been removed.If the seal is broken the hissing sound you hear will be air leaking in rather than gases leaking out.If the glass has been weakened there is a small chance of implosion but this reduces as more air leaks in.The air flow and hissing sound should stop when the pressure inside and outside the tube equalise.
     
  4. Feb 17, 2012 #3
    Thank you so much. I feel like such a dork but was just not sure what was going on. I feel a lot better. Thanks so much.
     
  5. Feb 17, 2012 #4

    Bobbywhy

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    Gold Member

    The Cathode Ray Tube (CRT) operates with a vacuum inside. This is because electrons flow from the cathode, located in the rear where the glass/metal interface is and the anode, the viewing surface. Now, if your glass/metal interface is broken it may be leaking, just as Dadface said above. The volume of the CRT is not so large, and if air has leaked into it it will cease to display a picture.

    If you continue to hear a hissing it may be arcing of High Voltage. You will see a large rubber-insulated wire connected to the CRT near the front face. This wire carries around 15,000 volts (15KV) to the anode from the High Voltage Power Supply. You can check for arcing by listening along this wire with a cardboard tube against your ear. Often this is caused by a loose connection. DO NOT TOUCH that wire! If you can localize the source of the hissing sound, turn the set off and wait. The HV circuit usually has a "bleeder" resistor which bleeds off the HV. Do NOT trust this, however. After ~10 minutes you should use a long probe, grounded at one end, to touch the HV connector to discharge it before touching.
     
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