I'm not familiar with your unit so I can only guess. With AC there is
not negative and positive. Actually the potential alternates between
positive and negative 50 o, in the US, 60 times per sec. Sometimes
pulsating DC is used to light discharge tubes. This is done by means
of an induction coil or nowadays with an electronic circuit. I would
guess that, if the tubes can only be installed one way in their socket
that is, if they cannot be flipped over or something, then they have
a positive and negative terminal. If it does not matter which end goes
in what socket, then there is not positive or negative. All the FL tubes
we have in the US can be installed either way.
Bob Schramm