[HAM] Newbie with M111 Vibrato problem

[WHITE, JAMES P]

Hi Group,
Bought my first organ Friday, a Hammond M-111 - Now the quest is on to
learn to play.  I have hired a teacher and lessons start tomorrow!

On to my issue - the upper manual plays well with the "Vibrato OFF" tab
selected (in the down position) but has very low volume with the tab in
the UP position.  I *think* the same problem exists with the lower
manual.  To compound matters I don't even know what Vibrato means.
Maybe it's code for "silence"?

BTW I have basic vacuum-tube technology repair skills due to my hobby of
restoring antique jukeboxes...  All I've done so far is blow out the
dust and oil the generator (and make random noises) 

Thanks, 
JP White
Hammond, LA