I have a 24 volt dc power supply that intermittently has 120 volts AC on the DC side. I will see the AC at the DC output terminals for maybe a 1/2 second. My 12 volt DC power supply does not have that issue. This 24 vdc power supply provides power to a PLC used in my automation application. It only provides power to the PLC and 24 vdc is not used anywhere else in the circuit. What could b causing this anomaly and is it normal.