1, fuse tube blown: carefully check the circuit board above the various components, look at the appearance of these components is not burnt or electrolyte overflow, smell – smell there is no peculiar smell; and then measure the resistance value of the power input to see the phenomenon of a local short-circuit; and then measure the power supply filter capacitors can be normal charging and discharging, switching power tubes whether the breakdown of the damage, the UC3842 and the surrounding components whether breakdown, burnt, etc., if the components are damaged replacement can be. Components can be replaced if they are damaged.

2, no DC voltage output or voltage output is not stable: first of all, use a multimeter to measure the high-frequency pulse transformer components are damaged, to rule out the high-frequency rectifier diode breakdown, short-circuit loads; and then measure the output DC voltage to see if the power supply control circuit failure; and then use a multimeter to measure the high-frequency filtering circuit in the rectifier diode and low-voltage filtering capacitors is damaged, if the above components are damaged, replace the good If the above components are damaged, replace the new components can be excluded.

3, no DC voltage output, but the fuse is intact: first of all, we should determine whether the charger’s variable control chip UC3842 is in the state of the king or has been damaged. If these feet are not broken, and the charger still can not start normally, also indicates that the UC3842 has been damaged, should be directly replaced.

4, the cooling fan does not turn: first with a multimeter to measure the control fan transistor is damaged, if the tube is not damaged, it may be the fan itself is damaged, you can pull down the fan from the circuit board, and another 12V DC power (note that the positive and negative poles), to see if it is rotating, but also to see whether there are any foreign objects stuck; if swinging under the fan wires, the fan is rotating, the wire is inside a broken line or poor contact. Broken wire or poor contact with the connector. According to the above situation with the replacement of components.

5, the power supply does not start: plug the power supply, the large capacitor has 300V voltage, unplug the power supply again to measure the large capacitor 2 terminal or 300V voltage does not fall. After discharging the capacitor, replace the starting resistor. Start resistor in the power input part, resistance value 150K, power 2W.

6, the power supply does not start: plugged in, the large capacitor 2 end of the 300V voltage, unplug the power supply, the large capacitor voltage slowly decline, the circuit board to check whether all the phenomenon of de-soldering, after the completion of welding, will be replaced by a new 3842, power on the test machine can be.

7, flashing lights: first of all, the circuit board welding again, try again, if still flashing lights, please check the output sampling resistor. 0.1 ohms. 3W power. Connected to the negative extreme of the output line, the resistor can be replaced with a new one.

8, high output voltage, power, voltage higher than 70V, charging does not turn the lights, the first circuit board welding again, try again, if the voltage is still high, please replace the photocoupler, try again, or high output, replace the 431 reference regulator, try again.

9, the output voltage is not stable: first circuit board welding again, after the test machine, and then the output capacitor 63V470UF capacitor can be replaced with a new test machine.

10, charging does not turn the light: use the detector to test the data, and then the 358 or 324 for a new test machine.