Welcome to our site! EDAboard.com is an international Electronic Discussion Forum focused on EDA software, circuits, schematics, books, theory, papers, asic, pld, 8051, DSP, Network, RF, Analog Design, PCB, Service Manuals... and a whole lot more! To participate you need to register. Registration is free. Click here to register now.
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 ?