How to Implement a Reference Designator Change?

Using Kicad 5.0.1 on my Ubuntu 18.04.1 LTS OS. My schematic diagram in Eeschema has a reference designator prefix assigned to all the basic reference designators like this: A3R1, A3C1, A3AR1, A3K1, A3PTH1, etc. (you get the picture). I have my board partially laid out with two mounting holes and a number of plated thru holes, all of which I locked in place. All other footprints are off the board to the side.

I went back to my Eeschema schematic diagram and deleted the ref des prefix from all the reference designators, thus A3R1 is now R1, A3C1 is now C1, etc. Went to CvPcb and the footprints were all assigned properly to their basic reference designator. I did not change any footprints. I then did a new net list. Changed over to my board layout in Pcbnew, and according to the instructions in the Pcbnew document, I imported the new net list and did not change any of the criteria (all criteria were at their default condition).

Here is what I got: A new set of footprints with basic ref des including the footprints of the locked parts. I was able to delete the footprints with the old reference designators except for the locked parts/footprints. How do I accomplish what I am trying to do? What criteria do I mark on the import of the netlist? I guess I could unlock the footprints I have already placed but I thought locking just meant locking in place, not a change in the ref des. What are the steps I need to do?

–Thanks, Larry

Here is the mistake.

A good option is footprint selection by timestamp: your new R1 has the same timestamp as the old A3R1 if you only modified the reference. (I mean, not deleting A3R1 and make a new R1 symbol).

Other option is delete extra footprints, but you should be carreful with the mounting holes (I guess they have not a symbol in the schematic). I cannot check right now if the locked footprints are not deleted.

Finally, you can perform a dry run. The messages will tell you what footprints will be deleted, added, etc. without touching the layout. If ok, re-run with dry run unchecked.

Thanks for your suggestions and explanation. I deleted all the footprints not on the board. I did the NET download selecting timestamp, keep extra footprints, keep single pad nets, and dry run. everything looked good so I unchecked the dry run and downloaded the NETlist. All the footprints on the board changed to basic ref des and they were locked as I moved all of the ref des on the front silk screen (F.SilkS) to be beside the footprint instead of centered over the footprint. When I did this the notice came up saying the footprint was locked and if I wanted to continue I had to check yes.

I have been around long enough that I put mounting holes on the schematic. The graphic symbol for a mounting hole, plated or non-plated, is a filled in circle, a connection point. If a mounting hole is a plated hole that connects to ground then this is properly shown.
–Thanks again, Larry

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