KRC4 Compact motherboard replacement - Caught in reboot loop

  • Recommissioning our KR6 after a motherboard failure and long storage. Dropped replacement board + processor and rebooted. System seems to be caught in a loop. Flashes KUKA logo then "Windows Starting" on repeat.

    Any thoughts?

  • one thing to try is to see if it can run long enough to enter BIOS and it remains stable while there.

    if necessary also try disconnecting HDD (not much else to remove).

    things that come to mind are mechanical faults such as not correctly seated CPU or memory. CPU socket is easily ruined since contacts are tiny and easily deformed if installation is not done correctly.

    it is easier to check if RAM is plugged in correctly and if motherboard is properly mounted and grounded. then there is a risk of static if not following ESD measures, that will easily damage RAM or motherboard. one could also check if anything is overheating, maybe there is a short or faulty PSU. you can try checking PSU voltage for any surge or fluctuation. CPUs can fail too but so far never needed to replace one, problem was typically the motherboard or RAM or lose power connections..

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  • Thanks for the reply. I was able to keep it stable in bios. It passed a memory test, but will not boot in any of the safe modes. finally found the USB. Going to restore with a factory image as a last ditch effort.

  • Digging into this KRC4 Compact controller again after the break. Controller boots perfectly from the recovery stick. Went on to restore WIM in silent mode. Did not help, as I'm still caught in loop, Flashes "KUKA screen > Windows Starting" repeatedly. Should I look at failed memory stick? Start unplugging other components to isolate reboot issue? Any insight would be appreciated.


  • if it boots perfectly from USB Recovery stick it would appear that both KPC and USB Recovery stick are fine.

    if restoring image still produces same problem, chances are that image itself is corrupted.

    Or maybe KPC does have a memory issue and it just so happens that the faulty location is high enough, so that it is not causing problem when KPC is booting small footprint OS like one on the USB recovery stick. When you get inside BIOS, check if detailed memory test option is available and activate it (at least for test). when this feature exists, it is often turned off to speed up booting (detailed memory test may take couple of minutes). If this is not found in the BIOS, you can add 3rd party memory test program to your USB stick and run it from there.

    Or it could be that your USB recovery stick is out of date and fails to recognize newer KSS. when that happens computer stops or reboots after only a short time (minute or so). In comparison when restore works, it takes some 15-20min to decompress image and write it to HDD. if using stick in silent mode check the log.

    btw KUKA used to offer software updates for USB sticks:


    With that one could upgrade old USB recovery sticks (1.x and 2.x) to 3.x. Then they released 4.x and since then i did not see updates any more. Considering cost of the USB recovery stick and constantly newer KSS versions released, updates were very nice thing. But this link does not seem to be maintained any more so if that is the issue, you may want to contact KUKA.

    Also it could be that HDD/SSD itself is defective. In this case even though USB recovery stick works fine, and tries to write good data, writing to HDD/SSD may not be working correctly on certain locations. Just a guess...

    There could be some other things too like CPU not seated correctly (possibly socket pins deformed) etc.

    good luck

    1) read pinned topic: READ FIRST...

    2) if you have an issue with robot, post question in the correct forum section... do NOT contact me directly

    3) read 1 and 2

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