**LG TV, after a cold start, the screen shows retrace lines, which disappear after 10 minutes of operation.**
**Analysis and Inspection:** When the fault occurs, adjusting the contrast, brightness, and color saturation of the TV is normal. Testing the R, G, B signal inputs also shows normal results. The collector voltages of the three primary color output tubes are around 150V, which is within the normal range. Upon checking, the voltage of the G2 electrode of the picture tube is found to be too high. By adjusting the acceleration electrode voltage, it is observed that the retrace lines on the screen disappear but the raster does not become darker, indicating that the fault lies in the automatic brightness control circuit and the picture tube acceleration circuit. Further inspection reveals that components C425, R403, D405, and R433 are all in good condition. When the fault occurs, the adjustable range of the acceleration electrode voltage is weak, but after 10 minutes, the adjustable range returns to normal. It is suspected that the internal contact of T402 with the acceleration electrode is poor, causing the acceleration electrode voltage to be too high during a cold start, leading to this fault.
**Repair Method:** Replacing T402 resolves the issue.
**Source Article:** [http://blog.sina.com.cn/lgdianshiwx](http://blog.sina.com.cn/lgdianshiwx)