CD50 can be kind of a pain in the ass to work on. I have 4 that I have fixed so far and two more sitting on the bench. Biggest problem I see with them is the spindle motors slowly wearing out and going bad with no replacement other than a donor unit.
Unless your friend likes to screw around inside a CD player or has the funds to pay someone else to do it for him I would suggest he look into a CD5500 instead. More reliable and actually easier to work out the mechanics on.
I like the CD50 for its looks and funky front loading tray and diplay lamping much more so than the later 5500 and on but there are a lot more mechnics that can go worng or get out of kilter than any of the other B&O players. I will probably be tuning a tweaking these things along for as long as I own them or as long as the lasers hold up.
My bottom line opinion for this machine is that thay are in their late 20's and regular tuning and maintenance is probably going to be the reality. They do sound nice when working properly