Tv picture shrinks to one small line across the middle the screen.
The TV will be fine for a while but then the picture will shrink into one small line going across the TV screen If we tap the side of the TV the picture goes back to full screen. Obviously that cannot be the permanent solution.
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This is caused due to random falure of vertical scan circuits. It generally is caused by dried out capacitors or bad driver IC. Unfortunately it will get worse. If you fail to turn the TV off quickly you will burn a permenant horizontal line on the tube. Trip to the repair shop I am afraid.
Sounds to me you have a cold solder joint ( loose solder connection ) on the printer circuit board around or on the vertical chip or on one of the vertical capacitors. You may also have a bad vertical chip or a bad vertical capacitor, but I doubt it since it did come and go. I'de get a soldering iron and some solder and touch up the connections. I will remind you that you need to always excersise saftey by making sure, before removing the back, unplug the TV from the wall, and use care not to come in contact with the large red wire going to the back of the picture tube as the picture tube can be turned off and still store lots of voltage ( up to 35,000 volts). Always stay safe and when soldering, use care not to run solder across places that will make a short.
Good Luck and I hope this helps
Ed Meshechek ( Radio Man )
Since the set works initially, there are likely poor solder connections at the vertical IC. If this is not addressed soon, the IC will fail and need to be replaced. The vertical IC is a small flat IC with about 11 pins or so that may be marked LA7837 or something similar. Try resoldering the pins first. If that fails to resolve the problem, replace teh IC. Feel free to post the marking here so I can verify you have the correct one.
The vertical output IC LA7847 is failing. It will likely fail permanately and you will have just the horizontal line. The set will require service. Just do not run the set very long in this state. That thin white line can likely burn into the crt phospher and will show all the time thus ruining the glass picture tube...
Most problems indicated by your description involved the Vertical IC. With your post "tap...pop back up" signifies a loose connection or to be more specific a cold solder. I suspect that no part(s) need top be replaced but would however require re-application of heat with the use of a soldering iron.
Hope this be of initial help/idea. Pls post back how things turned up or should you need additional information.
hi there, you do have a vertical section problem and at the power supply section problem. do some test, check for some cold solder at the power supply section, test some electrolytic capacitor at the vertical section. ty
You have a bad solder connection in the vertical circuit. This will require you to resolder these bad connections before it blows out the vertical output IC or other parts in the circuit. Do this ASAP before you make a small repair into a large one. If you have no solid state printed circuit board experience, please play it safe and take the set into a pro to do this for you. Good Luck
Open the TV amd turn it on in a position you can see the picture, possibly through a mirror. Now gently tap all of the metal heat sinks on the circuit board until you find the one that is sensitive it will have a small chip mounted vertically on it, with probably like 7-10 pins. The number on the chip will most likely be an "LA****" number. Now turn the circuit board (UNPLUG FIRST) over and resolder the pins. This is your problem 99% of the time. Be very careful there is High Voltage inside this TV.