I recently replaced a defective laser pick-up in my PC-FX. The previous unit suffered a diode burnout, however the former owner said that he noted tracking issues when playing some games prior to the unit's failure. I purchased a OE game new (Animé Freak VOL. 1) for testing purposes and during some FMV sequences there is audio cut-out and an occasional pause with video playback.
On the system board underneath the left panel, there are 4 pots. These are what I assume to be the laser gain and adjustment. If anybody knows which is which or has a service guide this will be an enormous help. For anybody who has experienced a a laser pickup failure, the replacement unit is a Hitachi HOP-E1, available at Donberg electronics
http://www.donberg.ie/. I paid about $ 50 to have it shipped to the US. The replacement part requires minor modification to the data cable end and the old lens servo protector plastic cover to work.
My goal is to create a technical document that will help PC-FX owners service their laser assembly and eliminate the need to flop the unit around to play games.