Switching Power Supply Maintenance Steps
1, maintenance of switching power supply, the first multimeter to detect whether the power components are short-circuit breakdown, such as power rectifier bridge stack, switching tubes, high-frequency high-power rectifier tubes, inhibit the inrush current of high-power resistors are burned. And then test the output voltage port resistance is abnormal, these parts if any damage will need to be replaced.
2, the first step is completed, after the power supply can not work properly, then we have to test the power factor module (PFC) and pulse width modulation components (PWM), consult the relevant information, familiar with the PFC and PWM module and each function of the module and its module to work properly necessary conditions.
3, then, for the power supply with PFC circuit, it is necessary to measure the filter capacitor voltage on both sides of about 380VDC, such as about 380VDC voltage, indicating that the PFC module is working properly.
Then detect the working status of the PWM component, measure its power input VC, reference voltage output VR, start control Vstart/Vcontrol terminal voltage is normal.
4, in the switching power supply maintenance practice, there are many switching power supply UC38 × × series 8-pin PWM components, most of the power supply can not work because the power supply start-up resistor is damaged, or chip performance degradation.
5, when the filter capacitor on the voltage of 380VDC or so, indicating that the PFC circuit does not work properly, PFC module key detection feet for power input feet VC, start feet Vstart/control, CT and RT feet and V0 feet.
Repair a Fuji 3000 camera, test a board on the filter capacitor without 380VDC voltage, VC, CT and RT waveforms as well as V0 waveforms are normal, measuring the field effect power switching tube G pole without V0 waveforms, due to the FA5331 (PFC) for the SMD components, the machine with a long time after the emergence of the V0 end of the board between the soldering, the V0 signal is not sent to the field effect tube G pole.
