MS9050UD Circuit Board Repair

Looking for some assistance in repairing a MS9050UD control board. Had a power surge on the AC input. The board display was completely dead and the pair of 18AH batteries discharged when removed The system has a surge protector on the input circuit. The board worked after the surge until the batteries were discharged. Removed the board and found the voltage regulator with the heat sink IC “U12” had a portion of the face blow off. I was able to match the part number and replaced “U12”. I powered the board up by the AC input at our shop with no field wiring connected as the board was on a piece of cardboard. Everything was working fine and the display showed all the missing points, NACs, battery, and phone lines. Took the board back and mounted it back in the cabinet and connected the field wiring and changed batteries. All I could get now is a quick buzz from the piezo and no display. Component “Z20” just above the header above the display smokes. I removed the board from the cabinet and tried to power it with AC as I did at the previous repair with no luck only a quick buzz from the piezo and smoking component “Z20”. Any suggestions would be appreciated[quote=“David_Gertz, post:2, topic:9457, full:true”]
Looking for some assistance in repairing a MS9050UD control board. Had a power surge on the AC input. The board display was completely dead and the pair of 18AH batteries discharged when removed The system has a surge protector on the input circuit. The board worked after the surge until the batteries were discharged. Removed the board and found the voltage regulator with the heat sink IC “U12” had a portion of the face blow off. I was able to match the part number and replaced “U12”. I powered the board up by the AC input at our shop with no field wiring connected as the board was on a piece of cardboard. Everything was working fine and the display showed all the missing points, NACs, battery, and phone lines. Took the board back and mounted it back in the cabinet and connected the field wiring and changed batteries. All I could get now is a quick buzz from the piezo and no display. Component “Z20” just above the header above the display smokes. I removed the board from the cabinet and tried to power it with AC as I did at the previous repair with no luck only a quick buzz from the piezo and smoking component “Z20”. Any suggestions would be appreciated :slightly_smiling_face: