1, first 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;
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2, then measure the resistance value of the power input, if less than 20OkΩ, it indicates that there is a local short circuit phenomenon at the back end, and then measure the positive and negative resistance value of the 4 rectifier diodes and the resistance value of the two current limiting resistors to see whether there is a short circuit or burned out;
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3. Finally, measure whether the power filter capacitor can be charged and discharged normally, whether the switching power tube is broken down or damaged, whether UC3842 and the surrounding components are broken down or burned out