Voltage output is unstable
Check
whether LM431R pin
has voltage
Check LM431 and
sampling resistor
Check
whether LM431R is
normal
Change LM431
Check
whether photoelectric
coupler is
normal
Change photoelectric coupler
Change U501
9. Troubleshooting flow chart for “Voltage output is unstable”is shown in the following figure 3.3.2.9:
Figure 3.3.2.9 Troubleshooting flow chart for “Voltage output is unstable”
Y
N
Y
N
Y
N
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