⑴ Adjusting the AC Voltage: Use an AC voltage regulator to adjust the AC input voltage, monitor the B+ output voltage to maintain it slightly above the normal value (as if the sampling is normal, the negative feedback voltage stabilization loop should take control). Then measure the voltage across the b, e, and c terminals of the transistors at each stage of the pulse width adjustment circuit, the voltage drop between the ① and ② pins of the optocoupler, to see if it corresponds to or follows the same trend as the voltage stabilization principle. If at a certain point the measured value contradicts the expected value according to the stabilization principle, it indicates a fault in that stage of the measured point, which cannot correctly transmit the voltage stabilization information, leading to stabilization failure. Check the related components one by one. 36V aviation power supply, 400HZ frequency converter power supply, 115/200V power supply, 27V DC power supply, 400HZ power supply, aviation power supply
② Segmentation Method (applicable to direct sampling power supply): Using the optocoupler in the voltage stabilization loop as the dividing line, segment the circuit to determine the fault range. Short-circuit the ③ and ④ terminals of the optocoupler, and observe the change in B+. ·A significant drop or cessation in B+ output indicates that the heat base section is normal. The fault lies in the B+ sampling circuit and the optocoupler. ·If there is no noticeable change or the change is minimal, it suggests a fault in the heat base section. Thoroughly inspect the pulse width adjustment circuit of this section. Focus on checking the circuit that forms the working voltage of the pulse adjustment circuit, such as filter capacitors and rectifier tubes, which should be replaced using the substitution method. Also, check the replacement of all adjusting tubes and related components, and inspect for any copper trace breaks.
