Measuring line scanning circuits of rows in the output tubes, line drive, line oscillation circuit related voltage is normal. Using oscilloscope to measure the oscillation, the output waveform has the normal, suspected of switching power supply output voltages have clutter or poor filtering. Using oscilloscope to measure +lllV clutter-wave signal at the output. To check the SMPS, Q801 logging and Q802 and Q803 the voltage are normal, and are very stable, but each waveform sine wave interference, and sine wave is the common source of stress. Because the transistor gain is too high or caused by distributed capacitance. Q801 and Q802 and Q803 correlation analysis, Q803 performance Q80l caused by poor, poor Q802 waveform, Q80l, Q802, poor performance does not cause Q803 waves gone bad, judging by Q803 has a problem. Welding tests, and found that the pipe is ZSD400, its beta value is large, using old type Q803 circuitry, troubleshooting.