how to judge the tube is dead?


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how to judge the tube is dead?

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Guest
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Mar 11, 2003, 4:14 PM

Post #1 of 6 (930 views)
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how to judge the tube is dead?	Can't Post

I'm an ECE student. I want to know how the tech judges the tube is dead. Hope some experts give me answer. thanks.

mickhayafe
TV Repair Authority

Mar 11, 2003, 6:28 PM

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Re: [Guest] how to judge the tube is dead? [In reply to]	Can't Post

you could write books on this one subject, but i'll be the first to chime in on an easy one.

if you take the back of the tv off and turn the tv on and hear loud sparks and see in the neck of the tube blue streaks of light that look like lightning it's a bad tube.

Guest
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Mar 12, 2003, 10:29 PM

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Re: [mickhayafe] how to judge the tube is dead? [In reply to]	Can't Post

Student is student. Authority is authority. Tongue

mickhayafe
TV Repair Authority

Mar 13, 2003, 3:20 PM

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Re: [Guest] how to judge the tube is dead? [In reply to]	Can't Post

well, since no-one else is replying i'll give you another.
if the set turns on and you have picture, but the colors "bleed" together, or if one color streaks to one side, red is the most noticeable. you got a bad tube, just make sure your screen voltage is normal, and your 200 volt line to the crt board is ok. but on older sets this is a big problem, you'll probably fix old sets then see streaking in the tube, but the cust. is used to it so they think it's normal. funny huh.

to test a tube, whether new or old, turn up the color to %100, any questions on the quality of the tube will be more pronounced as you get higher and higher. as far as new tv's, if you go to an electronics store, ie. circuit city. take afew of the high dollar new flat screen tubes, and do this, you'll weed out poor quality tubes real quick. sony's are the best.

that's kind of a two-in-one reply :)

Guest
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Mar 13, 2003, 7:07 PM

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Re: [mickhayafe] how to judge the tube is dead? [In reply to]	Can't Post

I'm surprised nobody has stated the obvious....use a CRT tester. Sencore Beam Builder's are one of the most popular machines that are used to test most CRT's for shorts and low emission and rarely give false readings.

mickhayafe
TV Repair Authority

Mar 15, 2003, 2:39 PM

Post #6 of 6 (908 views)
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Re: [Guest] how to judge the tube is dead? [In reply to]	Can't Post

I had a tv yesterday, newer set, sony kv20fs100 when you turned it on, the picture was fine, and all voltages were ok on the crt board, ie. r g b + screen was about 300v. after afew minutes the picture would fade and look very dark, upon measuring the voltages again, i saw the tube was shorting out the 300v screen voltage. when i took the crt board off the tube, the screen voltage would come back up to 300v. Tube was bad. a practical example for you

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