The 5400 uses a 4.5V Alkaline battery for backing up the computer's PRAM. The original batteries are prone to leaking in their age and need to be removed immediately from any LC 520.
The 5400's case is now extremely brittle. These will not, and I repeat will not survive shipping. You can add all the packing material that you want, but I have only heard a single case in recent years of one of these arriving intact when shipped. If you are looking to purchase one, do it locally.
When disassembling, use extreme care with all parts. Any parts that are clipped in place should be hit with a hair dryer first to soften up the plastic a bit, or they will break.
Nearly all of these have also turned yellow to some extent. For those cases, a retrobrite process can restore them to the proper color.
Many original SCSI hard drives for these have gone bad, especially those made by Quantum, which suffer from sticky rubber bumpers in the head assembly.
The floppy drives in these often get too full of dust to work. A cleaning and relubrication will often bring back dead drives.
Index < Macintosh Portal < Power Macintosh < 5400 < Common Faults & Maintenance