Hello RAKIB,

did you make any changes to the system or did it suddenly appear?

RAKIB

I have changed the cpu. I checked with the same cpu in the hardware configuration. But its all the same. The machine was shut down for several years. Then when it was started again tere was the fault.

 Hello,

 I don't know  your problem, so, have you download in your CPU OB 82, OB 86, OB 121, OB122 and can you post to us your diagnostic buffer?

Hello,

problem can be back side bus connector or check each modules front connector (with joined wires to it) to be correctly safely inserted completelly inside modules. I expect OBs installed in case of CPU is running.

Hello RAKIB

Can you check 24V DC (L+ & M) in your faulty module. If 24V DC good condition then follow below step.

1. First disconnect your faulty module from PLC panel (HW rack).

2. Take a new any kind of S7-300 CPU (313C better).

3. Connect your faulty module with new S7-300 PLC CPU in your table.

4. Now create a HW configuration in your software and download your new CPU.

5. inject a analog signal 4 to 20mA or 0 to 10V your faulty module and monitor.

6. If you can't monitor analog value that means your module damage. You have to change the module.

Please give a picture with online HW monitoring.

Thank you

hi RAKIB,

can you show us in a scetch how the modules are wired?

have also a look in the manual how the modules have to be wired.

SIMATIC S7-300 Module data

hope this helps,

regards,