01-21-2017, 06:19 AM
Try squirting some WD40 or other penetrating oil between the tube shield and it's base, it's probably rusted on. I don't know if this is one of those but some tube shields had a sort of bayonette lock on them where you have to push down and turn to get them off, however those usually had a spring inside, alternatively you may have to rock the tube shield back and forth to get it off, but try the WD first.
Regards
Arran
Regards
Arran