When the image brightness, contrast, normal flyback lines, failure in blanking circuit. The airport blanking is field flyback pulse generated by the pulse amplification sound Q401 via C413 add to Q402 collector, for Q402 flyback power supply, and then through R419, R612 partial pressure, C626 put matrix circuit coupled to see IC301 6 feet as a blanking signal, therefore can not be blanking flyback line fault is out in the circuit. fy4service manual download site
(1) using oscilloscope measurement IC301 6 feet no blanking pulse input. Normal should be 26 VPP blanking line field. If blanking is normal, the fault in the integration block IC301 inside. fy4service manual download site
(2) using oscilloscope tube measuring Q402 collector, no 50 VPP pulse voltage, diode D409 bad suspicion. Removed after the measure, found that has hit CHUAN, a new diode after troubleshooting. fy4service manual download site
(3) the breakdown backcourt scanning D409 flyback power supply for 57 v, pump power is invalid, thus longer field flyback and image are beginning to scan flyback period, coupled with poor blanking, so we can see an upper an image edge, overlapping phenomenon. When there is no oscilloscope for the failures, can first find the pump power supply section tube Q401, D401 isolation diodes and C413, R432, C412, etc. fy4service manual download site
(4) under the condition of no oscilloscope, wan to jilt table available measure the resistor, capacitor, transistors and other components, to find the fault, also can use multimeter dB judge pulse in the presence of.fy4service manual download site