Ok got it! Now i have a new problem. The arm doesn't lift anymore. It is lowered now and when I turn the Beogram on it just rams into the side of the record. I quickly turned it off but it keeps spinning, the arm won't move back either, seems to be locked. 

it may be that your problem is described here and the solution given

/forum/imported-unmapped/my-me-6000#post-1741862

but it is also conceivable that the tonearm bearing is broken off, as described here:

https://archivedforum2.beoworld.org/cfs-filesystemfile.ashx/__key/CommunityServer.Components.PostAttachments/00.00.26.82.06/BG3300.jpg

Solution suggestion

https://archivedforum2.beoworld.org/cfs-filesystemfile.ashx/__key/CommunityServer.Components.PostAttachments/00.00.26.82.07/BG3300_2D00_1.JPG

You got the black lifter arm on the wrong side of the tilting white bar.

Martin

Martin, you were absolutely right. 
Ok, everything seems to be in place BUT it it is still not working. 

What happens now in order: I put power on the Beogram. The slider with tonearm is in the far left position. The motor that turns the platter is turning. The tonearm is lifted. 

I press 'turn', nothing happens. I press 'lift' nothing happens. I press 'play', the letters '33' briefly show on the display arm but nothing else happens. I press '45', the motor spins faster. I press 'off' (the dott) and the slider moves back but only for about a third of the way. 

Meanwhile the motor keeps spinning. I press 'off' again and the slider moves back further. Pressing it more often doesn't work.

When I press 'off' the smaller motor (blue arrow) spins, but the excentric ring doesnt move. The white slide with teeth moves out (red arrow) shortly before moving back again. All this time, the cog left doesn't move. (green arrow)

My guess; I pushed the cogs (black plastic ones) out of 'alignment'. I mean that i rotated them by hand a bit to try and loosen the slider and that now they are not grabbing teeth properly.

I tested all this without the platter installed, with the top removed (but wires to buttons still attached ofcourse) Maybe there is a sensor that does not let the Beogram play if there is no platter on?

See attached pic. 

The subplatter drives all the mechanics.
Fit the subplatter and the platter belt and try again.
Carriage parked position is far right (outside the platter).

Martin

Yes!!!! It works now. Perfect. I will try some more records but the arm and needle come in far enough it seems. 

Are there more common problems I will encounter in the future?

Everyone who helped; I am very grateful for your time. Appreciate the help.

Yet another time an old thread here on Beoworld solved my problem. My Beogram 5500 started to lowered the needle to soon for a while and then stopped working last week. Mounted a small screw and nut instead, and gave it a clean and some new belts. Now playing like new again :) Thanks!