ashish

i am using this PLC in my hydraulic machine since the last 3-4 yrs. recently, since the last 8-10 days i m facing this problem that one particular output doesnt fire at times ( machine is in a closed loop system) i changed the relay that fires the hydraulic solenoid, SMPS that fires hydraulic solenoid, solenoid valve but cant figure out the problem. can somebody advise me whether there is a problem with the PLC ?