1, the fuse tube is blown: carefully check the various components on the circuit board to see whether the appearance of these components is burned or there is electrolyte overflow, smell - smell no odor; Then measure the resistance value of the power input to see the local short-circuit phenomenon; Then measure whether the power filter capacitor can be charged and discharged normally, whether the switching power tube is broken down and damaged, whether the UC3842 and the surrounding components are broken, burned, etc., if the components are damaged, you can replace them.
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2, no DC voltage output or voltage output instability: First of all, use a multimeter to measure whether the various components of the high-frequency pulse transformer are damaged, excluding the high-frequency rectifier diode breakdown, load short circuit; Then measure the DC voltage of each output to see if the control circuit of the power supply is faulty; Then use a multimeter to statically measure whether the rectifier diode and low-voltage filter capacitor in the high-frequency filter circuit are damaged. If the above components are damaged, replace the new components to eliminate them.
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3, no DC voltage output, but the safety wire is intact: First judge whether the charger's change control chip UC3842 is in the king state or has been damaged. If these feet are not broken down, and the charger still cannot start normally, it also indicates that the UC3842 has been damaged and should be replaced directly.
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4, the cooling fan does not turn: first use a multimeter to measure whether the triode of the control fan is damaged, if the tube is not damaged, it may be the fan itself is damaged, you can pull the fan off the circuit board, and connect a 12V direct current (pay attention to the positive and negative electrodes), to see whether the rotation, but also to see if there is no foreign matter stuck; If you swing the fan wire, the fan will turn, it indicates that there is a broken wire or poor contact of the connector inside the wire. Replace the components according to the above conditions.
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5, the power does not start: plug the power supply, the large capacitor has 300V voltage, unplug the power supply and measure the large capacitor 2 end or 300V voltage does not drop. After discharging the capacitor, replace the starting resistor. Starting resistance in the power input part, resistance value 150K, power 2W.
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6, the power does not start: plug in, the large capacitor 2 end has 300V voltage, unplug the power, the large capacitor voltage slowly drops, the circuit board all check whether there is a phenomenon of welding, after the completion of repair welding, the 3842 replaced with a new, power test machine can be.
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7, flashing: First the circuit board welding again, test again, if it is still flashing, please check the output sampling resistance. 0.1 euro. 3W power. Connect to the negative end of the output line and replace the resistor with a new one.
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8, the output voltage is high, the voltage is higher than 70 V, the charging does not turn the lamp, the circuit board is repaired and welded again, and the machine is tested again, if the voltage is still high, please replace the photoelectric coupler, the machine is tested again, or the output is high, replace the 431 reference voltage regulator, and the machine is tested again.