#### Updated 170903. If the schematic sheet (or sheets in a multi-schematic) Project contains more than one instance of a component with the same prefix, a `Prefix Conflict` error will be generated when trying to generate a PCB for the first time or update an existing PCB after a change to the schematic. This is a simple example of a schematic having two components with the same prefix: ![enter image description here][1] * In this schematic, there are two components with the `R4` prefix, so the `Prefix Conflict` can be resolved by changing either one of them to `Rx`, where `x` is a unique number in the schematic. It may be tempting to save a back up or a copy of a modified schematic to the same project as the original schematic but then when an attempt is made to convert the project to a PCB, a `Prefix Conflict` error will be generated for each component: ![enter image description here][2] This is because, when converting schematics in a Project to PCB, EasyEDA will merge *all* of the schematics under a Project into *one* PCB. * To avoid this error, save or move backup copies or earlier versions of schematics into a new Project to keep them separate from the working schematics. Then create the new PCB from the most up to date schematic in the original, working, project. [1]: /editor/20170430/5905ed4972a05.png [2]: /editor/20170430/5905ed62ee8a9.png