Contrologix PLC losing servo teach points afer power glitch

We had a power glitch last night at the factory. 15 minutes later when the power came back, all the PLCs came back to life except for one PLC.

When I went online with the RSLogix 5000 software, I found that the logic was still intact, but some of the servo teach points were lost. The teach points were -13.0 (most of them anyway). Usually in these tools it is a positive number.

I am not sure if this issue is related to the PLC battery, because if it the battery then it will clear the entire program completely after a power down. But this case was special, where only the servo points were messed up.

Any suggestions?

The battery doesn't hold the program. It simply allows the controller to retain it's data when power is removed (as it sounds like you understand).

Perhaps your controller has a CompactFlash card on the front and the system has been configured to reload the program from the flash card on power-up.

Do you see a CompactFlash card plugged into the front of the controller?

EDIT: The CompactFlash is on the bottom of some units which would require you to pull it out of the chassis. And if it is an older controller the memory module (equivalent to the compactflash) is actually built-in so those units are a little harder to visually detect the presence of a memory module.

Perhaps if you can go online with the controller and examine the Controller Properties window and check the setting on the Nonvolatile Memory tab.

OG

OG,

No. We dont use Compact flash cards in any of our PLCs. The slots are empty.

Operaghost said:

EDIT: The CompactFlash is on the bottom of some units which would require you to pull it out of the chassis. And if it is an older controller the memory module (equivalent to the compactflash) is actually built-in so those units are a little harder to visually detect the presence of a memory module.

Perhaps if you can go online with the controller and examine the Controller Properties window and check the setting on the Nonvolatile Memory tab.

OG

Click to expand...

OK. I will check this out and update! Thanks OG.

The most common cause of a "partial" data loss is from a remote device via communications in my experience (now that you ruled out Load from Non Volatile Storage)...

I have never seen an Allen-Bradley PLC, SLC, or PAC have any corruption and go into run mode. They'll fault every time. The program integrity is almost binary. 1 or 0, it's there or it's not. RUN mode or RED LED of death.

Every case of a suspected "something's wrong with the program...it's running but...", that was brought to me, has been tracked down to EEPROM, or other non-volatile restore, or a remote device. It's especially surprising when a machine hasn't lost power for many years, and then there's a corruption which prompts a restore, or the execution of a fault routine or the first scan bit does something no one but the integrator has ever seen...

Is there an HMI connected that suffered through the same power interruption?

I had to change the "write to controller on power-up" option for Panelview Standards at least 5 times over the years, and found one PV+ set up that way...I had a PV550 with an internal intermittent open that kept rebooting and changing the speed and width while the ply cutting machine kept right on making stock. One operator almost got fired for setting up the machine wrong, she'd made several rolls about 20mm too narrow. She swore she had checked the width according to SOP, but then it changed by itself...she was right...

Also, what is the method of connection to the servo drives? Is it possible that those values were read from a drive on power up, and the drive is the device that got "scrambled"?