As far as I can see, you can reset selected components to their existing Prefix followed by '?'. You cannot however bulk rename their prefixes (in your example) from J to JACK either using the Find Similar Objects tool or by manually doing a CTRL+Left-click select and then renaming the common Prefix attribute. This fails with an error message that 'The Prefixes are not allowed to repeat!'. What you can do is to select each in turn and paste 'JACK?' into each Prefix - either directly in the schematic or in the Prefix attribute in the right hand panel - and then select a single re-prefixed JACK? component and use Find Similar Objects tool to find and select all instances of the Component with the Prefix 'JACK?' and then do **Annotate > Selected components only****\> Re\-annotate all**.

Ok, thank you for the answer! But even if i do this, i cannot update the prefixes of the pcb components from the schematics without loosing there place on the board? or did i miss something?

@arthurbachelet, I can't  think of an easy way to change the prefixes in the PCB without the Footprints all being moved off the PCB by an Update PCB or Import Changes. You could try doing Reset Component ID in both the schematic and the PCB after changing the prefixes in the schematic but before doing an Update PCB or Import Changes to stop the affected Footprints being moved outside the PCB. If that does not work then I think you will have to manually change the prefixes of the Footprints in the PCB. You could select just the J part of each one and paste JACK. That way you don't accidentally change the number part of each prefix. You may still have to do Reset Component ID in both the schematic and the PCB after changing the prefixes to stop the affected Footprints being moved outside the PCB next time you do an Update PCB or Import Changes.

Thank you Andy for the tips, i gonna try to proceed as you say, and i will report here if it's working for me. It's not much of an issue anyway, it just take some time to rename everything manually... Cheers.

@arthurbachelet, I just tried a few things... This seems to pass the changes to the Prefixes in the schematic into the PCB without ripping up the placements: 1. Do **Update PCB...** or **Import Changes...** to check that the Schematic and the PCB are the same; 2. If the message says that there are no differences and you have **not** already changed the prefixes in the schematic then go to step 8; 3. If the message says that there are no differences and you have already changed the prefixes in the schematic then go to step 9; 4. If there is a warning that there are changes to be made then press **Cancel** in the **Confirm Importing Changes Information** window; 5. Do **Reset Component ID** in both the schematic and the PCB; 6. Save both the schematic and the PCB; 7. Do **Update PCB...** or **Import Changes...** to check that the Schematic and the PCB are the same (the message says that there are no differences); 8. Change the Prefixes in the schematic; 9. Do **Update PCB...** or **Import Changes...**; 10. The Prefixes in the PCB should change without ripping up the placements.

Amazing :) Its working great this way and the windows does say "replace component" instead of "remove component " indeed. Many thanks for the time you took solving the problem! Cheers!

This procedure seems to work also to replace the footprints without messing the placement of components wich is great!