error code 6000 MELSEC Q12PRHCPU MEMORY COPY RESULTED TO FILE DIFF. ERROR 6000

[Ravi@aoa 0]

Folks, we have a set of Mitsubishi Q12PRHCPU (redundant) running effortless since many years. CPU-A as standby and CPU-B as Control. Recently we noticed BATT low alarm on CPU-B. So we arranged for a spare battery Q6BAT and started the procedure as per manual(attached procedure and flow chart).

We did memory copy from Control to standby (as prescribed precaution) and did the Reset of Standby PLC CPU-A. Memory copy from B to A completed successfully 100%.

But the BACKUP LED did not turn Green from Red & Error LED kept flickering on standby CPU-A. CPU-B remain in Control but backup LED turned RED.

From system monitoring we found that there is a Error 6000 (FILE DIFF.) observed in One of the .QPG (program 00-MDBUS.QPG). We tried to reset it but were not successful.

We are surprised that why does the program differs when it was copied from CPU-B to CPU-A using the memory copy.

Still we did the VERIFY and found no difference between the programs in CPU-A & CPU-B. 

Can anyone explain the cause of this issue and the solution.

Please note that the CPU-B is still in control and plant is running. Backup LED on both CPU are red which means (redundancy loss) and error LED on standby CPU-A is flickering RED. There is no error in the CPU-A (Control) -we checked this using the GX Developer.

Also attached here are the image of the error and error help.

Thanks in advance.

Battery Replacement procedure.pdf

Battery Replacement procedure-Flow Chart.pdf

Error.pdf

MELSEC QCPU ERROR CODE 6000 FILE DIFF.pdf

[Gambit 334]

The batt led will not turn off after replacement of the battery you need to reset the  PLC or clear the error.
Did you RST the stanby- system ?

 

 

[Ravi@aoa 0]

@Gambit we already cleared the bat. Alarm by doing reset from the SCADA.

The problem is that after copy memory the standby CPU has "file diff." Error 6000 And backup LED is stable RED. We already tried reset and power on-off of the standby CPU.

We checked the program in both CPU after memory copy and its exactly matching. 

So we don't understand the reason of file diff. since the memory copy was done from Control CPU to standby. 

[Gambit 334]

You didn't format the stand-by plc right ?

 

[Ravi@aoa 0]

@Gambit no we didn't formatted the memory. Refer the battery change procedure attached with my 1st post. We followed the procedure and only did memory copy from Control CPU to standby. 

[Gambit 334]

But you did do a rst after the mem  copy of the stand by system right ?

 

[Ravi@aoa 0]

@GambitYes we did rst after copy memory.