The clicking sound is made by the laser eye moving up and down, failing to get a sharp focus on the disc.
Originally Posted by Antoniomike7
The disc needs to be cleaned, the laser might need to be cleaned, and/or the laser needs to be replaced.
@Dreamwebber : The slimlines (Other than the SCPH-70000 series) have the best lasers - compared to the FAT PS2s.
SCPH-10000 S. MINOKAMO v1.01 (Defunct)
SCPH-10000 S. KISARAZU v1.00 (faulty)
SCPH-15000 S. KOHDA (With warranty seal!) :D
DESR-5100 S. EMCS