Siemens PLC Problem


Thread Starter


We have Toilet roll Rewinder machine in our factory. And we have S7-300 PLC and CPU 314.
When we switched on the Machine, the CPU doesn't work. There is no light indication in DC 5 V and RUN LED's. What is problem in CPU? please give the diagnostic ideas?

Daniel Chartier

Hello, Nijam;
No light on the DC5V LED usually means no 24 V power reaching the CPU module. Check the connections from your power supply to the CPU; if they are correct, and the power supply does prodduce enough current at the right voltage, the your CPU is probablyy defective.
You can download the S7-300 hardware manual (for more diagnostics information) from Siemens at the following address:


Hope this helps,
Daniel Chartier