CRT TV with only a horizontal line through the center of screen.
27" Sanyo CRT TV. All of a sudden, the picture went from normal to a bright horizontal line across the middle of the screen. My gut tells me it is likely to be a bad IC or capacitor, and therefore a costly repair not worth doing, unless it is something I can do myself. Any advice ??
Re: CRT TV with only a horizontal line through the center...
Hi,
Yeah. Unfortunately you are right. It is normally the ic that controlls power to the gun. And it is expensive. Your only chance is to find another model of the same TV that some is ready to trash or throw away at low cost and that TV having some other defect. Advertise in the local newspaper or other channels. It is worth a shot.
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Hello
You have stated that your TV has a lot of horizontal lines before it went off picture. We say that lines as retrace lines. So many of them will there on the entire screen, at about one inch or so apart, horizontaly scattered along with picuture. At that time, you may be unable to down the brightness control also. Even though you have reduced the brightness control to zero position, there will be some brightness level on the screen. You should have to repair that fault at the begining. There is a voltage going to the picture tube base, known as screen voltage. That voltage determine the emission of the picture tube, and we call it a bias voltage. When it goes higher than normal, this trouble ie retrace lines will occur. In long run it may spoil the picture tube itself. I don't know what the case of yours.
Anyway it is best for you to consult an experience technician in this case. Ok.
this is a frame fault
the fact that you can still see the line when the tv is off is because you have been watching with the line and it has burnt into the crt.
It needs repair. If the line is vertical, then something is damaged on its horizontal circuit section on the mainboard. If the line is horizontal, the vertical circuit section is damaged. have it repaired to a qualified service center or person! avoid switching it to avoid further damage on other parts!
sounds like you may have a bad ic it probley is a surface mount on the bottom of the board it could couse this problem would need to take to a shop to repair. The ic probley is numbered ic101 on board.
You have a failure in the vertical deflection circuit. This could be either a bad vertical chip, the power supply that runs the chip or a bad capacitor in that circuit. This is usually a repair best left to a professional. There is a small possibility that it could be bad solder connections. If genlty tapping the unit temporarily solves the issue you can try and resolder the pins on the vertical chip LA7841 is the part number. There is also a resistor 1 ohm 1 watt. If that resistor is open you can assume the IC is bad
This is a problem with the vertical circuit. Look for a small flat IC attached to a heat sink. It should have about 9-11 pins and be marked LA7838 or something similar. Try resoldering the pins first. If that does not resolve the problem, replace the IC. The IC will cost between $10-$20.
Dan
I have a similar problem on my CRT computer monitor (AcerView 76c). It is an old screen and I think it is just at the end of its life, much like your TV. Having some background in physics, I would be pretty sure that the problem is with the cathode ray tube's vertical deflection system. The horizontal deflection electrodes are working while the vertical one is not. This results in a display of a single horizontal line (or in my case, a few superimposed) in the centre of the screen. Where both X and Y (horizontal and vertical) deflectors fail then the electron gun firing would result in a single bright spot in the dead-centre of the screen.
So really, we have no choice but to move on and buy a new set as repair is probably just as, if not more, expensive than replacement with a new device. Seeing as your post was in 2007, I hope you managed to solve the problem.
It sounds as you desribe, the vertical output IC and or the b+ feed capacitor off the Hi voltage transformer feeding the vert. IC its required voltage. Not a really hard job to replace, but not for a handi person to do. This should be left to the professional, as there are no user serviceable parts inside this set and with the HI voltage and the safety issues its best to call somesone to assist you with this repair. Good Luck
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