Fanuc 21-TB - Alarm 912 SRAM Parity : ( Low) - NEED HELP!
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  1. #1
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    Default Fanuc 21-TB - Alarm 912 SRAM Parity : ( Low) - NEED HELP!

    Went to start up our Fanuc 21-TB controlled EMCO-Turn 325 turning center, but it shows an alarm 912 SRAM Parity : (low) error. Attached is a screen shot.

    The machine has sat idle for a couple months and was not connected via RS232. I did replace the battery about 9 months ago.

    The good news is that I did a complete backup of the machine when we got it in 2016. I have files named: NC Parameters.NC, Original Programs.NC, and PMC Parameters.NC.

    I also have the original EMCO PCMCIA card with what looks like the ladder logic.

    My questions are:

    First, why did this happen?
    Second, where do I start to trouble-shoot?

    I've been searching for information here, but have yet to find a thread that walks through all the steps to fix this.

    Any help is appreciated.

    Thanks,

    Jim
    Attached Thumbnails Attached Thumbnails alarm-912-parity-low.jpg   parameters.jpg   pcmcia.jpg  

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    Well, that was not too painful. I found instructions about upgrading memory on a Fanuc 16/18.

    Did the RESET + DELETE to clear the memory and then re-boot with two right-most soft keys depressed to enter the System Monitor Service Menu.

    Did a SRAM restore from the PCMCIA card and reboot...BAM! Back up and running. No tool offsets, but appears to operate.

    Still don't understand why the SRAM got corrupted. Measured the battery voltage and it's a little above 3 VDC. Had a spare battery for another machine and installed that just in case. Plan to boot it up tomorrow and if it works, re-do the tool offsets.

    Feel free to comment.

  3. #3
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    By far the most common cause for corrupt SRAM on a Fanuc is a bad battery. On rare occasions I have seen an SRAM parity error for no clear reason, but very rare. Most of the time initializing the memory and restoring it fixes it. It's been very, very rare that a memory module had to be replaced. I think I maybe only did that once or twice.

  4. #4
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    Thanks, that's good to know.

    I'm thinking the shop got quite cold during the last cold-front that came through and the battery voltage dropped. It's got a new battery in it now & works good. I'll put a sticker on the machine to remind me about future battery replacement.


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