Horizontal line on screen denotes the absensce of vertical sweep itself. Check the vertical output section circuit to LA7840. Check for any loose solder terminals. It will be best to measure the input voltage to that IC from the LOT secondary supply. Try by replace the IC. If these do not help you, measure the frequency from the main IC. It should be at 50Hz. If this frequency is not present, the main IC is faulty. If you wish to get some more details about the circuit, check this link.
http://electronicshelponline.blogspot.com/ Pull
up older posts there, either by its left side bar, or see it in
Timslide
option. Schematic diagrams, that show vertical IC LA7840 is given. You can compare it.
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