Singer 90S Manuel D'instruction page 20

THREADING THE TOP THREAD
presser foot lifter is not raised, correct thread tension
cannot be obtained.)
illustrated.
IMPORTANT:
To verify that the machine is threaded properly in the
tension discs, do this simple check:
1.) With the presser foot raised, pull the thread towards
the back of the machine. You should detect only
needle.
2.) Now lower the presser foot and again pull the thread
towards the the back of the machine. This time you
should detect a considerable amount of resistance
and much more deflection of the needle. If you do
not detect the resistance you have mis-threaded the
machine and need to re-thread it.
18
A
B
C