Picked up a working cld-2850 with a non working display. Not illuminated...
Not that the player is a keeper but I would like to find out what is wrong ?
Any ideas?

Hmmmm . . . had a similar problem on a different make and model altogether (Sony MDP-A3.) Took it to a generic electronics repair shop to see if they could figure out the problem (wasn't even a Sony authorized repair shop.) Found out that the problem was a bad capacitor.

Maybe your fix could be as simple (that is if you know how to replace a capacitor and if those capacitors are still available)?

Wonder if someone clipped the cap so they didn't see the display??

Been about it. Going to check the voltage feeding the display...
I guess it might be cap on the PS board