Altium is driving me crazy right now. I Annotate my schematic, but I do not know why Altium wants to always switch / exchange U109 sub-parts. RC4558 op-amp. I put them in one order and Altium changes it. WHY? I have tried everything that comes to my mind. Many times removed the part, updated the PCB. Saved and closed Alitum and then put a new part in the same place. So why is this happening and only to U109, even if I change it to let's say U113, this only still happens to this op-amp and it's sub-parts? Is this a bug? What could I do to prevent this from happening? What is the reason and the problem? enter image description here

  • \$\begingroup\$ What if you unchecked the modify boxes (I know nothing about Altium so it's highly likely it's a stupid suggestion). \$\endgroup\$
    – Andy aka
    Dec 12, 2019 at 15:49
  • \$\begingroup\$ Yep, that would work of course. But then I have to do it every time I annotate the schematic. Probably that's a workaround as long as I understand the real problem. Could be a software bug. Actually your suggestion is good! Thanks! (Like why didn't I come up with that LOL) :D \$\endgroup\$ Dec 12, 2019 at 15:53
  • \$\begingroup\$ Maybe there's some global setting that disallows gate swapping being done this way? \$\endgroup\$
    – Andy aka
    Dec 12, 2019 at 16:11
  • 3
    \$\begingroup\$ You can lock the sub-part designation if you look in the properties of the part in schematic. This re-jiggering of sub-parts by annotate has been a long-standing issue in Altium. \$\endgroup\$ Dec 12, 2019 at 16:31
  • \$\begingroup\$ Thank you very much @ChrisKnudsen. This sheds some light upon the topic. Locking the sub-parts SOLVED IT! Thanks a lot! :) \$\endgroup\$ Dec 16, 2019 at 20:23

1 Answer 1


You can lock the sub-part designation if you look in the properties of the part in schematic.

Select the part, and press F11 to bring up the Properties panel. enter image description here Click on the 'padlock' symbol to change the symbol from 'unlocked' to 'locked'. This will prevent the annotator from changing the assignment.

You can also select multiple parts, and do the same thing: enter image description here

Alternatively, if you invoke: Tools -> Annotation -> Annotate Schematics, then in the Annotate window, you can check the 'lock' symbols next to each sub-part. enter image description here

Altium Designer 20.0.9


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