Complete PLC project backup before depot repair — technical checklist for Siemens, Mitsubishi and Delta

The majority of extended post-repair downtimes trace back not to faulty replacement hardware but to missing or incompatible program archives. This article details full backup procedures for three widely deployed platforms. For TIA Portal, it explains how to export complete project archives including HW Config, custom libraries and Safety programs, and why MD5-hashing the resulting .ap17/.ap18 archive is essential. For GX Works, differences between GXW and GX3 formats across FX, Q and iQ-R families are covered alongside CC-Link and MELSECNET parameter capture. For Delta, AS Series parameter archiving and transfer to hardware successors is addressed. A recommended multi-version folder structure with date-stamped naming, and an online checksum comparison procedure after hardware return, complete the guide. The article also discusses how we verify programs post-repair at the depot level, including function-block-level simulation before live recommission.