question about the psp fat and psp slim?

[misfitmedic]

Hello, i have a problem with my psp slim. I have two psp. the original fat black one and a blue slim one. the slim psp's laser reader or umd reader does not light up like some website says to test it nor does it read my umds. i was wondering is it possible to switch my black psp laser with the slim psp? the black psp laser works. I have look on alot of sites about the difference about them but theres no info. thanks to your response!!!