[Leica] Light leaks in many ways

[Louis DiBacco <louis.dibacco@snet.net>]

Hi, I am new to the group and I have a problem I am trying to figure
out. I think my camera has a light leak. It's an M6 (bought new in 1990)
and after I process my b&w film I have noticed black, exposed areas on
my negatives, along the top edge of the film, usually continuing only up
to the 5th or 6th frame, around the sprocket holes. The pattern of
exposure is not consistent from roll to roll. When looking at the
negatives, it's always at the top when the image is right side up. That
would mean that light is possibly coming in at the bottom of the camera
because the image is exposed upside down. Right?

Has anyone experienced this or have any suggestions on how I can prove
or not prove my M6 leaks before I send it away (gasp!!!) for repair?

Thanks.

Louis DiBacco