Analysis and Maintenance : The understanding of users, the power of lightning from entering . Visually check the power Houmodianlu cracking, black fuse fuse F801 , resistors R802 open, full-bridge rectifier D806 has two two polar tube breakdown optocoupler D803 ①, ② legs open, after replacing these damaged components, power supply and load no obvious short-circuit fault , the decision power test machine . In order to secure, off -line output circuit , terminating at + B output 60W bulb false load test machine , and monitor + B voltage. When turned on, the lamp brightness twinkling change , + B voltage instability . Analysis of the regulator or the protection circuit failure . First check the regulation loop , no exceptions , and then check the protection circuit ( see figure ) . The aircraft better protection circuit complexity , with overvoltage , overcurrent, short circuit protection. The circuit consists of Q831, Q805 overcurrent detection circuit , D837, D830 load short-circuit detection circuit , D831 overvoltage detection circuit and optocoupler D811, Q827, Q826, Q804 components. D811 16V power supply from the normal by R864, D825 -powered , B point to a high potential , D811 internal light tube light, the transistor saturated conduction , A point of low potential , Q827, Q826, Q804 are turned off, the internal switch on Houmodianlu no effect . When each overcurrent , overvoltage , short circuit detection circuit operates , B points dropped to a low potential , D811 deadline , A point goes high , Q827, Q826, Q804 is turned on , the thick film in a very short circuit stop switch b vibration . When disconnecting Q804 c pole, power supply output voltage returns to normal , the fault really in protection circuit. In the protection circuit consisting of Q827 and Q826 SCR circuit simulation , once into the protected status , in the case of uninterruptible power protection status can not quit , while the machine light bulb dummy load , dark change, indicating analog thyristor circuit failure check analog thyristor circuit , open circuit found D823 , D811 ③, ④ foot open. Replace the D823, the D811, no flashing lamp brightness changes, the output voltage is also stable at 110V. Remove the dummy load , turn the line output circuit television repair.

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