The C13 read error on Sony minidisc means that the Table Of Contents (TOC) cannot be read.
The Minidisc is a magneto-optical device that uses combined laser and magnetic technology to write ad re-write the tracks, and magnetic head only to read.
If the problem is only with a specific disk or with few disks, then this is probably because of faulty media. In that case the content on the specific disks may be lost.
If this happens with every disc, including blanks, or with the majority of disks, then it is usually because the magnetic heads are dirty or faulty.
Additionally, when problem is the head, the motor will spin the disk, if motor does not spin at all, then the microswitch that starts motor and the motor itself must be tested.
To clean the heads (there is more than one on a minidisc) use
Sony Dvm-12cld : Minidisc Head Cleaner.
If that does not work, the heads must be replaced doing a precision soldering inside minidisc deck, and without moving or damaging nearby laser assembly, and other parts in there. In that case better having the job done by a technician, as this is a very delicate repair, the part from sony is not expensive.
