I'm quite sure that one can't run lensechanger on a SCPH-50000 series because of the Dragon MECHACON it has, so you have to use the same type of laser it originally had (KHS-400C -> KHS-400C, or Sanyo HD7 or KHS-400R -> Sanyo HD7 or KHS-400R). If your original laser was a R-type laser (Sanyo HD7 or KHS-400R), that is the reason why it isn't working.
Originally Posted by Bitterman
Personally, I love this HD7 laser that my SCPH-39006 has, as it seems to be able to read all sorts of discs which only the SCPH-50000 series is able to.
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