With grating line field scanning circuit work normally, no image shows faults in the electronic search like video channel circuit, in order to quickly distinguish existing parts, should check resistance as found in the presence of characters, according to the character shows that AN2510S internal video amplifier circuit is normal, fault before video amplifier circuits. Insert camera scene video playback, use the oscilloscope observation AN2510S 18 feet for video signal input: input should be checked when external circuit or plug-in whether good contact; If AN2510S 18 feet normal is 0.2 V, 1.8 V 18 feet. If, according to the characters or images are no use oscilloscope to check AN2510S 24 feet for video signal waveform output: if there is no signal output, and fault in AN2510S internal; If the output signal is normal, should check at the end of the class depending on the pipes Q703 each pin voltage is normal, C715, C722 whether open or damaged.WjMservice manual download site