Induction cooker no power failure analysis: induction cooker power-on is generally due to the failure of the power supply circuit, reset circuit, crystal oscillation circuit. Therefore, it is necessary to measure the key point voltage with a multimeter to determine which part of the circuit has a problem, and find the corresponding fault part can be repaired according to the following conditions.
Determine the fault location: open the casing, check whether the safety tube is burned out, if the safety tube is intact, connect the power supply, use a multimeter to measure whether the output pin of the three-end voltage regulator 7805 has 5V
The voltage output. If there is no voltage output, it indicates that the fault may occur in the power supply part. If the measurement 7805 has 5V
Voltage output, use a multimeter to measure the 8th pin voltage of the main chip, if the measured voltage is 0V, it indicates that the fault may be caused by the reset circuit. If the measured pin 8 voltage is 5V, it indicates that the reset circuit is normal, and the fault is likely in the crystal oscillation circuit.
1. How to solve the problem that there is no reaction after the induction cooker is powered on due to the failsafe tube failure
(1) Most of the causes of this failure are damage to the igbt itself or problems with synchronization, oscillation, and drive circuits. Due to this failure is more serious, generally with other components damaged together, such as igbt, rectifier bridge pile also breakdown, put on a new fuse, do not immediately connect the power test machine, otherwise it may cause burning fuse. Replace the fuse with the same specification, and then use the multimeter to check whether the igbt, rectifier bridge pile breakdown, if there is damage, the damaged components are removed and replaced with the same type of components. Then use the multimeter to check the clamp diode D21 and the resistor R12, and the two components must be removed when measuring to make accurate measurements.
(2) After replacing the new components, you can refer to the detection method of the drive, oscillation and synchronous circuit maintenance process for detailed inspection, and the wiring panel can be tested after confirming that the circuits work normally.
2. There is no reaction after the induction cooker is powered on due to the failure of high and low voltage power supply circuit
(1) The electrical multimeter measures the output of the u2 regulator (7805) without 5V voltage output, at this time can measure whether the input of the three-end regulator 7805 has 18V voltage input, if there is 18V
The input without 5V voltage output may be u2(7805) damaged in the case of excluding the normal supply circuit of the rear stage. If there is no 18V power input, the fault is in the front switching power supply circuit.
(2)18V input voltage Please measure whether the positive electrode of D31 has 19V voltage, if there is 19V voltage, you can judge that it is D31 open circuit. If there is no 19V voltage, measure EC22
If the positive electrode of the capacitor has 19V voltage and the measurement has 19V voltage, it indicates that the voltage transformer l101 has a problem, and the fault can be removed by replacing it.
(3) Without 19V voltage, it can be measured whether the 5th to 8th pin of the chip (Viper12a) has nearly 300V
The voltage input. If this voltage input is available, use a multimeter to measure D30, D33, C50, and Z10 when the power is off
Whether normal, the above components are normal, indicating that the chip (Viper12a) itself is damaged. If there is no 300V voltage input, you can measure whether the fourth pin of the rectifier bridge stack has 300V
Voltage output, voltage output detection D101, R101, EC101. No voltage output, check rectifier bridge pile 1, 2
Whether the foot has 220V AC input, if there is AC input, it can be judged that the rectifier bridge pile is damaged. No AC input, check the 220V voltage input loop.
3. The failure of the reset circuit leads to no reaction after the induction cooker is powered on
In the case of measuring the 8th pin voltage of the main chip is 0V, it can be measured whether the base of Q3 has 2.2V voltage, if not, it can check R61, Z1, R16. If the voltage is normal, you can use a multimeter to carefully check the following components: Q3, R4, C7
If the components are checked to be normal, the main chip can be replaced.
4. The crystal circuit failure causes no reaction after the induction cooker is powered on
Check capacitors C2 and C3
Whether there is leakage, breakdown phenomenon. If only one of these two components is faulty, it will cause abnormal work. If the above capacitor is normal, then remove the crystal oscillator (8m) and replace it with a new crystal oscillator of the same specification. If the crystal oscillator itself is damaged, the fault can be eliminated after replacing it with a good crystal oscillator. If it still cannot be turned on, you can only replace the main control chip