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Message |
    
shoshannah
Citizen
Username: Shoshannah
Post Number: 255
Registered: 7-2002
| | Posted on Thursday, October 9, 2003 - 10:57 am: | 
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Just got our first flat-screen tv (not plasma). There is a very faint horizontal line that floats upward on a continual basis -- when it reaches the top of the screen, it starts again at the bottom. Is this my reception or is it the tv? What should I do about it? I never noticed it on my old tv, but then again, I never scrutinized the reception on my old tv the way I am doing on my new one. |
joy
Citizen
Username: Joy
Post Number: 117
Registered: 5-2001
| | Posted on Thursday, October 9, 2003 - 11:07 am: |
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Sounds like a 60Hz cycle hum bar.
Could be a problem with the power supply on the set.
Does it happen both with all TV programs and video/DVD playback?
If yes - there's a problem with the set.
If no - then it couble be a problem with the cable reception. |
jgberkeley
Supporter
Username: Jgberkeley
Post Number: 3184
Registered: 5-2001
| | Posted on Thursday, October 9, 2003 - 11:45 am: |
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You describe to the exact detail a problem with the vertical re-trace electronics of an analog tv.
I do not know, but I would bet that the electronics are somewhat the same.
Regardless, for the money you paid, this unit should not allow that line to be see, be it the tv, the cable or a power supply hum bar.
Take it back!!
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shoshannah
Citizen
Username: Shoshannah
Post Number: 257
Registered: 7-2002
| | Posted on Thursday, October 9, 2003 - 11:50 am: |
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60 Hz cycle hum bar? Vertical re-trace? Translation, please. I am an electronic illiterate. |
joy
Citizen
Username: Joy
Post Number: 118
Registered: 5-2001
| | Posted on Thursday, October 9, 2003 - 1:35 pm: |
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Basically - it's broken.
George is right - for the money you paid - take it back and have them give you a replacement. |
Brett
Citizen
Username: Bmalibashksa
Post Number: 309
Registered: 7-2003
| | Posted on Thursday, October 9, 2003 - 3:47 pm: |
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Some of the higher definitions have what’s called a “scan doubler”. I don’t remember the exact number but say a regular TV has 500 lines per screen. A HD TV has 1200. So if it’s not a HD signal the scan doubler will create the extra lines needed “Doubling the scan”. Sometimes these things miss some lines.
It does sound like a broken TV, if you can try the DVD approach before calling in the repairman.
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shoshannah
Citizen
Username: Shoshannah
Post Number: 262
Registered: 7-2002
| | Posted on Thursday, October 9, 2003 - 4:36 pm: |
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The television is just one of those new flat-screens -- it's not a high-definition-ready, not plasma, and not LCD. Just an old-fashioned tv with a flat screen. Don't know if that makes a difference. |
jgberkeley
Supporter
Username: Jgberkeley
Post Number: 3185
Registered: 5-2001
| | Posted on Thursday, October 9, 2003 - 4:50 pm: |
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TV’s are really single frame pictures painted on the screen then replaced quickly, much like a movie film. The painting is done using an electron beam that scans across your picture tube to paint the picture. The present NTSC 525 line format was developed as a black and white standard in the early 1940s and color was added in 1953. When the standard was originally conceived, the electrical engineers chose 525 lines so that the average viewer would not see the scan lines making up the image.
Electronics of the day could not support the 525 scan rate, so the engineers used electronics that could support 262.5 scan lines. That would look grainy, so they interleaved a second set of 262.5 scan lines between the first and thus had the effect of having 525 lines.
They succeeded in this respect, but the picture tubes of the time were considerably smaller than what we have today. As time has move along and electronics have improved, the 262.5 doubled to 525 rate has stayed due to the large cost of replacing every consumer TV and broadcast stations around the US.
HD TV use line doublers and really just signal processors that take an NTSC video signal (the output of a VCR or Tuner) and convert it into a doubled scan rate of the already doubled video signal. The result is an image that has 1050 horizontal scan lines vs. 525 for NTSC and appears smoother and more film-like.
The effect you are seeing is likely the vertical re-trace line. That is the electron beam moving back to the top of the screen to start painting the next image you will see. The electronics should shut the electron beam off at re-trace time. If it does not, you get that line.
(The above is a blend of data pulled from Google and my own knowledge on the subject)
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Brett
Citizen
Username: Bmalibashksa
Post Number: 313
Registered: 7-2003
| | Posted on Friday, October 10, 2003 - 8:53 am: |
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At least I was close with the numbers.
jg: Isn't that line sometimes caused by the voltage that returns the gun to the start position inducting into the gun itself? And isn't there a pot you can turn down to fix it?
Not that I think you should open the TV and tweek anything but you may not have to send it out to get fixed, they may send someone to your house |
jgberkeley
Supporter
Username: Jgberkeley
Post Number: 3186
Registered: 5-2001
| | Posted on Friday, October 10, 2003 - 9:40 am: |
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Brett, I wasn't busting your chops, just picking at a nit. 500 or 525, odds are you would not see the difference unless you were looking for it.
Yes voltage induction will do that. In fact, when the problem involves other electronic things such as power supply hum, fans, hair dryers or cable boxes near by, that is the problem. Voltage induction.
Higher end electronics often have the ability to adjust that level to find a spot where the line is no longer visible. Cheaper electronics use lets hardware (cheaper) and hope an average setting keeps the beam below the visible level. [Note, cheaper does not mean what you paid for it, rather how the Mfg. built it. I've seen some real cheap electronic designs in very expensive equipment.]
It is still my opinion that shoshanna needs to get in touch with the store where she bought it and either take it in or have a service person out.
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shoshannah
Citizen
Username: Shoshannah
Post Number: 265
Registered: 7-2002
| | Posted on Friday, October 10, 2003 - 9:57 am: |
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Thanks everyone. We bought it at Best Buy on Route 10 and will take it back this weekend. I'll let you know what happens.
P.S. The television actually was not very expensive. It's a Toshiba 20" -- $259.00. |
bobk
Supporter
Username: Bobk
Post Number: 3555
Registered: 5-2001
| | Posted on Friday, October 10, 2003 - 10:19 am: |
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Isn't it possible that interference from another device might be involved with this problem? If you have a lava lamp, a cordless phone, etc. near the TV, moving it might solve the problem. |
jet
Citizen
Username: Jet
Post Number: 275
Registered: 7-2001
| | Posted on Friday, October 10, 2003 - 10:19 am: |
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Thank you...Mr Spock |
jgberkeley
Supporter
Username: Jgberkeley
Post Number: 3187
Registered: 5-2001
| | Posted on Friday, October 10, 2003 - 1:47 pm: |
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Bobk,
We live in a world full of stuff. From my point of view, the TV should work in this world.
Either the design is cheap or the system is flawed.
The problem should be resolved by the TV people, not moving a lamp.
INMO |
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