TV vertical deflector. vertical line across scre

  second best 15:53 15 Jan 2007
Locked

Hello. I know this is a pc forum, but i thought at crt monitor would classify the same as a standard domestic tv.
I have an intermittent horizontal line across my screen. i still have sound, but the rest of the screen is black, bar this thin horizontal line. if i bang or even walk past the tv and knock it, the picture can either come back on or go bcak to this line. loud noises from the tv can set it off aswell. i have taken the back off, and been careful not to electrocute myself. I'm not sure what i'm looking for, but the main board situated on the base of the set seems to be the culprit. if i tilt it up and down i ge thte symptoms i'm explining. seems like a weak solder or something completley different. any advice would be great. i can't afford to get it fixed at the mo.
panasonic tx-29ad2dp/m

thanks.

  Stuartli 15:57 15 Jan 2007

I wouldn't mess about inside with either a monitor or a TV CRT - some of the often high voltages can either give you a very nasty shock or possibly kill you.

Try a local independent TV shop with a repair workshop as they should be able to sort it out.

Remember you can't see electricity coming...:-)

  second best 16:02 15 Jan 2007

thanks for the concern stuatli, if i stop replying, you know why :D. I'm led to believe it could just be a solder problem. i've been looking for the past week on the net. repairs could cost more than the tv is worth, and until the lcd's come down a lot in price, i'm stuck with it. and yes , i know my life is worth more that that. not much like. thanks again.

  Meshuga 16:03 15 Jan 2007

Sounds like dry joints, for the sake of your health, as Stuartli has said, leave it to the professionals.

  skeletal 16:36 15 Jan 2007

Stuartli has provided you with the warning! So with that in mind turn everything off and...

If I have understood you, every so often the picture “collapses” in to the thin horizontal line. Then with a “bang” can be made to come back.

I agree with you that this could be a soldered joint/broken wire and you will have a good chance of repairing it.

The problem is with the scanning circuits. What you need to do is find the coil of wire on the neck of the tube. You can’t really miss it; it is located at the junction of the narrow part of the tube (the neck), and where it splays out. The coil (actually there are several) surrounds the neck. If you look upwards (i.e. this is usually on the top of the tube as you would normally watch it) between the end of this coil and the edge of the tube (just before the part where you see the image) you should see a moderately large rubber/plastic cap with a fairly thick lead going into the middle of it. DON’T poke around this. This is the lead that runs at 25kV and it can remain at a high voltage for some time after you switch off. The same is true of its other end, which you will see goes to a moderately large, odd shaped object(s) which is the line output transformer/voltage tripler (hard to be more precise as there are several variants).

Back to that coil of wire. Direct you attention to the wires that are connected to it, and where they are connected on the circuit board. Anything round here that is loose will give your problem. On the circuit board, near to where the wires go, you should see some transistors (probably mounted on heat sinks). Check the soldered joints around those as well. In this area of the board, the transistors get hot enough to cause some expansion which, over time, can upset joints. You should find the wires go to two sections of board. One set should be nearer to the line output transformer than the others. It shouldn’t be those, it should be the ones furthest from the transformer.

Gently move the wires and see if you can see the boards track moving etc.

If it’s not those, it gets a bit harder because it will be the part of the board that generates the scanning signal. You need to find those ouptut transistors and move a little away from them and you may see more transistors/integrated circuits. Same technique, see if anything look lose around there.

It’s hard to be more precise; I hope this makes sense!

Skeletal

  rodriguez 16:39 15 Jan 2007

The tube inside a CRT TV or monitor operates at anything between 7,000 and 50,000 volts (depending on size) - don't mess with it. The power also has to be stepped up to power the tube (inside the back of the set where the power goes in, it's a lot higher than the 230v that comes out the wall). It uses capacitors to store these high amounts of electricity so even if you unplug it the high voltage is still there. The problem you describe is quite common and I think the tube needs to be adjusted and realigned (my TV had a problem where the screen squashed up over a period of time and the repair man realigned it at the back). I think this is done by turning a couple of screws in the back of the tube, but don't try it yourself it's too dangerous. Take it to a TV repair shop and if it's the same fault as the one I had, it should be about 40 quid or maybe a bit less.

  second best 17:30 15 Jan 2007

thanks alot for all your effort skeletal and rodriquez. it's good to know there is a solution. the fear of god has definitly been put into me, so i've decided to put the back, back on, and maybe see about a pro. skeletal, i have looked and chased down all day, most of what you suggested. but fear of getting too close to the transistors and coils prevents me from venturing further without knowing for sure the unit is powered down. i don't have the means or the know how to do this, so i've put it to bed. trouble now is, i've jigged and poked it about enough, i can't bang it back into operation. took the back off again, and it definitly seems to be localised on the main board near a big thing that looks powerful. if i lift the base of the tv slightly, elevating the board, i get my picture back, but let it drop again, and i get the line, and back and forth the same response. so i know it's knackered, and it can prob be fixed, just not by me. toooo scary.

thanks alot for all your time fellas. take care.

  skeletal 18:14 15 Jan 2007

That’s fair enough. Don’t do anything you are not comfortable with.

Skeletal

  ian-inhome 18:53 15 Jan 2007

The fault with your set is known as line collapse.
If the line stays on the screen when the fault occurs then the problem is usually in the line output circuit which handles very high voltages.
If the picture goes to the line, then fades to a blank screen the fault is likely to be in the line driver circuit. The fault at present is likely to be just a poor solder connection but you are unlikely to be able to see it. Either one will eventually lead to damage to other components in the set if not corrected. Get it repaired professionally before this happens and you end up with a set that may then be uneconomical to repair

  rodriguez 23:14 15 Jan 2007

One thing I should have added is about the danger of implosion because of the vaccuum (empty space with no air) inside it. Be very careful around the back of the tube as it isn't protected (unlike the front which has a thick layer of glass) so if it's struck hard enough to crack it the whole thing implodes. Also make sure that big sucker stuck on the top doesn't come off, this could give you the several thousand volt shock if pulled. The best thing to do now is take it to a repair shop and if it can't be efficiently repaired take it to the local dump and ask one of the staff to take it off your hands. Don't throw it in the skip, if it breaks it will probably go with a bang and there'll be glass everywhere. They usually stack old TVs up in a corner and then recycle them properly (that's what happens at my local one anyway).

  woodchip 23:27 15 Jan 2007

There is a problem in the field deflection module

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