No voltage output when powered on alone
Connect the control board to the power supply and upgrade the dedicated firmware for the control board. After restarting the test, the power supply will have average voltage output.
Disassemble the power supply and take out the circuit board and fan. Use a multimeter to measure whether the positive and negative poles of the output are short-circuited. If there is no short-circuit, measure whether there is a voltage input in the front section. The input voltage is generally measured on the pin with a large capacitor.
Measure whether the input voltage is around 420V. If it is about 300V. This indicates that there is no pressure rise in the PFC. To ensure safety, it is necessary to discharge the capacitor before taking the measurement.
First, check whether the control chip is shorted or poorly soldered. Check whether the VCC of the power supply circuit of the control board chip is normal.
Measure whether the transistors of the VCC circuit are normal. If it doesn’t work, it should be replaced. If the VCC voltage keeps jumping after the power-on measurement, the VCC circuit does not work. Therefore, since VCC is rectified by multiple diodes and outputs multiple sets of voltages, please discharge the capacitor after power off. It is necessary to measure whether each rectifier diode is working.
If the measurement result is that the filter capacitor is shorted, there is a problem with the rectifier output. Measure if the transistor is working. The transistors are on the front side and covered. The covering glue needs to be removed and replaced with a new transistor. Measure after replacement to confirm whether there is a short circuit.
Finally, perform a power-on test to confirm that the output is normal.
Voltage output is getting lower
If the fan is not working, check that the fan cable is plugged in properly. Or observe whether the fan speed is too fast.
The fan is spinning too fast due to high temperature. The power supply is locked to protect itself, so there is no output. Check the fan drive circuit to see if the temperature sensing cables on the four heat sinks are loose.
If there is no problem with the temperature control, there may be a problem with the chip program. You may need to reset the firmware.