As Beovintage I buy, repair and sell a lot of Beogram record players.
The problems are well known, engine too low in speed, belts and idler wheels worn out.
The last problems are solve by Dillen, Martin.
He sells round belts and they are perfect, measure is OK, but the stretch is very important, and OK as well.
This belt solves many problems, no lowering of speed, no noise and good switch between different RPM's
especially Beogram 1000 switching to 78 RPM works well.
Dillen also sells new idler wheels, to be used in players above. The old one's are sometimes hardened like stone and no more to be used. Big problem solved, they cost money but save your precious record player.