Upper Thread Tension - Bernina 900 electronic Service Manual

Upper thread tension
thread down very slowly. The pernmissible
Check and adjust the upper thread ten-
take-off speed is 30 sec ± 10 sec. for a
sion with settng weight No 39808004
ength of 55 mm
( length of thread
lever slot in frame).
The thread contained in the bobbin case
of a new machine should be used tor
testing, Place the bobbin with 3-ply.
white, left-twist No,60 sewing thread on
the front reel pir and thread as far as
Jf
the take-up lever which is in its hig hest
position.
IMPORTANT: Place thread into tensioner
on right-hand side of the intermediate
disk.
Withdraw approxirately 30 cm of thread
from the bobbin so that the thread hangs
loosely between reel pin (33) and guide
eye (34) when checking the take-off
speed.
Suspend weight on thread and observe
the take-off speed. Thread tension is pro-
perly adjusted when the weight pulls the
Fig. 54
133
34
16 ;,it
l
_
Fig 55
29