The circuit is pre-field oscillation frequency oscillations of the line drawn by the sawtooth discharge is formed by (24) # external RC components, the sawtooth internal push to get amplified by (23) # output to the amplifier block of ⑤ # LA7840 by ② # output, after the field deflection, and then, after the formation of the output coupling capacitor C457 and R459 after the amplifier circuit
Troubleshooting: The TV upper poor linearity, bootstrap component is faulty, check the boost diode and boost capacitor to normal. Lower than the normal measurement 24V, 24V power supply is suspected pre-supply problems caused by the inductor should be no problem, forward Charles finally found limiting resistor 24V rectified before use of larger, replacement troubleshooting.
Fault Summary: For field scanning circuit, the upper compression occurs, retrace lines, poor linear fault more, should focus on checking field amplifier power, bootstrap components, feedback capacitor, more power circuit faults which occur .
This sets us about the basic components of the scanning circuit and common troubleshooting, maintenance should distinguish this part is the power part of the fault, or the fault line scan and repair.