To attach a new belt in the BG CD50 is not for non technical people, if you have 10 thumps, stay away and get a technician, here goes. Tools and accessories. Take of the top cover, 2 screws in the back, loosen push up, tighten again, pull the cover to the back some 5-10 Mm. and lift up.

Take of door arm, green arrow, 2 screws, one at the left red arrow, for the arm guide, one at the right red arrow, at the door (flap), wiggle out the arm, then unscrew the 2 screws for the black "hooks", middle red arrows, wiggle out hooks

Looks like this

For the laser unit, unscrew 4 scews, red arrows, and the cable guide, green arrow.

Pull the laser unit a little to the left, lift it free, carefully, and turn it over to the right, place a pair of rubber pieces or a insulating sheet, between unit and PCB

Mark the gears, red arrows, if not or bad marked, you are into some job to get right again. take off the cam follower, blue arrow, one philips screw, loosen one allen screw (1.3 Mm. allen key) and turn the brass nut CCW, green arrow, until it comes of, lift out gear/cam wheel, this is divided in two parts, see next pic.

Lower part of the cam gear, red arrow, make sure you align the small guide spline to the cam gear when mounting the upper cam gear. The gear with the blue arrow can stay there, but now is a good occasion to take it off, clean and lubricate it.

All out, upper right gear is fastened with an E/clip, use a small screwdriver, and twist, be careful, they tend to fly around, never to be found again.

Old belt left, and new belt from Dillen right.

New belt in, look out for twisted belt, red arrow, turn the belt wheel to check, and turn the belt if twisted

After cleaning and lubricating everything its time to get it all back in, when you put back the gear/cam, take care to adjust the brass nut correctly.

First fit the Gear/cam properly to the lower cam part, check the gear marks are in the right position, then screw on the brass nut CW, until finger tight against the gear, then turn it CCW 1/2 a turn, secure with the Allen screw. If the nut is too tight the gear will not move freely, if to loose the disk lift will not go high enough.

Attach everything as it was before, turn the gears by hand and turn the disk tray to end positions, in and out, a couple of times, check that all wires are correct located and doesn't touch anything moving, leave the disc tray in the in position, connect to mains, press open tray, insert CD, press play, if it works OK you should see the counter moving, and the laser unit moving and focusing, press next track, until last track, and check the wires, that moves with the laser unit, can move without problems, move from first to last track and back a few times to get all the new grease and oil worked in.

Count your tools, and look if the only thing left is the old belt, put on the cover, connect your player and enjoy.

My BG CD50 worked without failures. So I wont do more, why repair anything that works perfectly.