To adjust the ignition coil is focused on the potentiometer, images, characters, the focus have change, but can not reach the ideal effect. Because the machine is equipped with dynamic Focus voltage (Focus) is controlled by a line, field scanning circuit TDA4859 32 feet output, via R566, C551 coupling to Q551 amplifier, then through R554 to ignition coil T501 (FBT) of 12 feet, adjust the size of the Focus voltage in order to realize dynamic focusing on line, field scanning. Multimeter is used to inspect the circuit related components no abnormalities are found. Measured again IC401 (TDA4859) 22 feet, there is also a focus voltage output, doubt C551 capacitance failure. Remove the C551 capacitance table was used to measure and found significantly lower capacity, after replacing C551 corners of screen images, characters, focusing on improved significantly. Another focus potentiometer to adjust ignition coil, focusing on up to par, troubleshooting.Arpservice manual download site