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This can be solved by following a few steps.
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1, according to the maintenance experience of various models of machines, the usual reason is the main return flow or power tube c pole overvoltage protection.
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2, use R-1R European gear to measure the power drop in the main loop. The whole bridge has no leakage phenomenon. The potentiometer VR1 in the current detection circuit found no problem.
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3, in the standby state to measure each power supply voltage 5V.18V.300V. Basically normal. Go down to the.2W connected from 300V. It is normal for both sets of output voltages with large resistors to be 1.5V-2V.
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4. In the standby state, the voltage of each power supply LM339 is also normal.
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5, in the no power on state to measure the resistance. Promote the transistor did not find the problem. Finally measure the diode. Voltage regulator. Found the 18 V. heating regulator diode. Cut the throat.
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6, find the same 18V pressure regulator tube installed on the test machine to work normally
Induction cooker for adjustable resistance and intermittent heating should check the IGBT tube, resonant capacitor, drive tube, Constantan wire and so on