Receive repair a millet TV of 40 inches of liquid crystal (L40M2-AA) , insert power source not to have reaction, key-press remote control all cannot switch on the mobile phone. Bring back maintenance with user come to an agreement or understanding...
Come home tear open machine...
Tear open machine observation power source board does not have original of burned-out, fission, measure advocate capacitance does not have voltage, insurance is not had burn, each effect is in charge of right voltaic sampling resistor not to have attaint; Class bides his time after voltage, 12V, be in a poor light wait for circuit commutate diode to all do not have puncture and right short circuit phenomenon.
Distrustful power source does not rise brace up or PFC does not rise brace up or voltage is too low, insert report to measure advocate voltage of filter wave capacitance is 326V, it is normal to wait for machine voltage 5V; By switch on the mobile phone hear squeak, TV does not switch on the mobile phone, without indicator light. Measure advocate 350-360 of voltage of filter wave capacitance changes, PFC voltage is too low, answer normally 380 above, 390-400V. Press repeatedly switch on the mobile phone key can switch on the mobile phone now and then, squeak greatens. Measure advocate the 360-380V when voltage of filter wave capacitance can switch on the mobile phone jumps change. Time is long can close automatically now and then machine.
Decide PFC circuit breakdown from this, suspect or PFC chip attaint, or voltage detects circuit breakdown. Cut off the power wait for 2-3 minute wait for advocate capacitance voltage drop comes sampling of PFC circuit voltage and chip periphery original are measured after safe voltage (above PFC chip word 3051) Baidu arrives without search data, discover voltage sampling has a capacitance to block is worth after, suspect capacitance leakage of electricity tears open next measurement not to have block value again, suspicion carries glue or dirt leakage of electricity on the back. Clear after dirt carries glue on the back to weigh new clothes to clean circuit board, measure return to normal. After checking circuit board not to have knickers and Yu Liuxi broken bits electrify switchs on the mobile phone to illume and do not have squeak again again, measure advocate 390V of voltage of filter wave capacitance is not fluctuant. The class after measuring each voltage all normal, try even WIFI machine half hours normal. Measure each voltage to all do not have wave motion, PFC also does not have squeak... maintenance ends.
Treasure is cleaned out to search this bat before 38 have ability the dot is changed directly board actuation, thought next immediate repair can grow experience to be able to save bit of money again already after, basically encounter later change board if lose the sense that learns maintenance.
