I have recently encountered in my repair work a Samsung Slim Fit CRT TV model# CS-29Z58MQ with a problem of three horizontal blanking lines appearing at the top edge of the screen. According, to the customer the problem started with just one line but after some time an additional two lines also appeared on the edge of the picture.
I inspected the board and tried to spot some bulging capacitors with signs of electrolyte leakage which usually cause this kind of picture abnormalities but found none.
Upon closer inspection of the solder side of the main board I saw signs of dry solder on resistors R428 (1.5 ohms, 1W) and on R413 (1ohm, 1W). These two resistors are connected in series with the Flyback transformer's 16.5V supply pin to the vertical output IC LA78045. The resistors are located at the rear edge of the main board beside the flyback transformer.
After resoldering the dry solder on the resistors the three colored lines on top of the picture disappeared.