Adjustment of Communication Voltage Method:
By adjusting the AC voltage regulator to modify the AC input voltage, we monitor the B+ output voltage to keep it slightly above the normal level (as the negative feedback voltage stabilization loop should take control at this point if the sampling is normal). Then, we measure the voltage across the b, e, and c terminals of the transistors at each stage of the pulse width adjustment circuit, as well as the voltage drop between the ① and ② pins of the optocoupler. We observe whether these changes align with the voltage stabilization principle or follow the same trend. If we find a point where the measured value contradicts the expected value according to the stabilization principle, it indicates a fault in that stage of the point being tested, preventing it from correctly transmitting voltage stabilization information and leading to stabilization failure. It is necessary to inspect the relevant components one by one.
Segmentation Method (Applicable to Direct Sampling Power Supply)
By using the optocoupler in the stable voltage loop as a dividing point, the circuit is segmented to determine the fault range. Short the ③ and ④ terminals of the short-circuit optocoupler and observe the change in B+.
