Simatic S7 I/Os not communicating with CPU

Hi

One of our Siemens S7-400 PLCs lost power and the backup batteries were dead. On resumption of power, once the Program was downloaded,

All the cards are giving the following messages in Diagnostic buffer,
Communication error, faulty module, external error.

The card status is okay in diagnostics, see attached.

Can someone help in pointing out what could be the problem.

I think you have a 24VDC power supply that is not working or not on.

Measure the voltage between the L+ and M terminals on the modules with red LEDs.

You have a "no external auxiliary voltage" as well.

After the power outage, did you download the hardware configuration?

It looks like a redundant S7-400H system and ET200M with active backplanes.
Redundant S7-400 is not a trivial. Can you get support from the supplier of this system ?

To recover a "dead" PCS7 system.
1. download hardware configuration.
2. download netpro configuration to all AS, OS and ES stations.
3. download program ("charts").
4. Start CPU 0
5. When CPU 0 is in run mode, start CPU 1.
6. Verify H status.

Create and maintain a system to routinely replace the battery backups.

Hi Ken

Thanks for the reply Ken. This is a redundant S7-400H system not PCS-7.
Though steps to recover the dead system seems to be same as you mentioned.

Just a few questions:
1. The hardware configuration and the netpro configuration download, Do we need to download it in both the CPUs one by one in a redundant S7-400H system.
Or downloading these only one CPU will work?

2. I also need to change a DO card from 10 channel (6ES7 326-2BF01-0AB0) as this is damaged, Can we change it to 8 channel (6ES7 326-2BF41-0AB0), we only use 4 channels anyways. The connector type is same for both, same part number. I have changed the card type and put the same addresses and the F destination addresses in the hardware configuration.
Is there any other thing apart from this I need to do?

3. Even though the backup batteries have been replaced, Every time we turn off and turn on the power to the unit, the CPU go in stop mode with steady led after some time once the power is turned on and we need to download the hardware config, netpro and program again,
Is there a time we need to wait after restoration of power to see if it goes to run mode or is there an issue with our RAM or any setting we need to do?

Any insight into it will be highly appreciated

Thanks

3. You should look diagnostic buffer from CPU. It tells why it is going to stop mode.


Wild quess. Can be that IO-cards are starting slower than CPU and it goes to OB-fault?


Why is power off even needed for reduntant system?

Per your original attachment, check the 24VDC power supply to your modules with red LEDs: