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thank you for the info.
The problem is : when TV just turned on, it jump . After it is warmed up, the picture stabilized . but still being compressed => it becomes rectangle , top and bottom are black . Do you think it is pure IC problem or some capacitor also ?
Next , do you have the circuit diagram or pcb layout of this verticle IC portion ?
Your problem seems to be around the vertical i.c. Try replacing the flyback/boost capacitor as well as the output coupling capacitor feeding the vertical york.
TDA3654, see attached. The boost cap is connected between pins 6 and 8 of the i.c.
I have changed a new IC and coupling capacitor, the screen no more flickering =>I think the problem has been solved
But there still have black portion at top/bottom screen.
When turn to TV test signal pattern, the circle is not so round . I supposed the TV needs some tuning . I remenber in old day, there are knob/resistor at the back of TV for user to adjust the pattern to expand/contract the pciture verically/ horizontally, this is to get the picture fill in nicely to the whole screen .
May I know where ( which variable components) I shall adjust to get the tuning done ?