First of all, suspected of TV/AV conversion circuit fault. After carefully check failed; Then pull the TV antenna, disconnect IC101 (sp) CPU, M37211M2-704 (49) foot (Y, character background blanking signal output) and (50) feet (B, blue characters of the signal output), lift the blue background, screen on a piece of white grating. Measuring IC101 (18) foot (SYNC. IN, radio identification signal input) voltage of OV, abnormal, check the peripheral circuit, as shown, find the switch triode Q428 (C1815) breakdown, c, e electrode has a short circuit damage. After replacing Q428, TV status back to normal. At this moment, IC101 has risen to 5 v voltage (18) feet. rNpservice manual download site
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[tip] in panasonic TC - 25 gf7or color TV, if the starting resistance open circuit of switching power supply, there will be a power load capacity and failure; Field output block TA8427K damage, there will be a sound, no grating fault.rNpservice manual download site