hi
actually the problem was the counter-platter that was too high (almost 0,7cm instead of the official 0,4 ) so i guess the belt had too little space to find its balance and spiraled downards.
i lowered it with the same technique described earlier (to raise it)
see
http://www.braun-hifi-forum.de/viewtopic.php?t=461
and it now turns properly. i first felt a little shy to handle the job but these ps are so wonderfully made it actually was a real kick (of course it was not a very complicated task).
pics in good playing condition very soon (still have to fix something in the headshell)
keep on groovin'
phil