If your newer model is newer than the v5, you can use LensChanger to reconfigure the PS2 to use the 'other' type of laser.
Early Japanese models (SCPH-10000, SCPH-15000 and SCPH-18000): Sony KHS-400A
Some early Fat PS2s (SCPH-30000 series): Sony KHS-400B
Some of the slightly newer fat PS2s (SCPH-3x000 series): Sony KHS-400C
Some of the slightly newer fat PS2s (SCPH-3x000 series): Sanyo KHS-400R
All the late fat PS2s (SCPH-50000 series and the v8 SCPH-39000 series): Sanyo HD7
KHS-400B lasers can be replaced with a KHS-400C, but the 'R' type lasers (KHS-400R and the HD7) cannot be used as a substitute without reconfiguring the console (Which might not be possible for some models).
I don't remember this clearly, but the SCPH-50000 series onwards cannot be reconfigured for other laser types (Other than the one that it came with) as the MECHACON was replaced by Sony with a really well-secured one.
Unmodified SCPH-77006 with SM 3.6
SCPH-39006 with M-chip modchip, SCPH-10281 NA and refurb Seagate 80GB HDD
SCPH-10000 v1.00 with SCPH-10190 PCMCIA NA and SCPH-20400 HDD unit