Aztec Airbrush Problem

I have a fairly new Aztec A470 airbrush that I think I screwed up. Maybe I
wasn't cleaning it enough or cleaned it too vigorously, but now it leaks
air all the time. It doesn't matter whether the nozzle is in the brush or
not, whether the trigger is pushed or not; air leaks from the "business
end" all the time (at least as long as I have air pressure to the brush.
If I shut off the air pressure to the brush the leak stops; I'm still
analysing that twist.)
Anyway, can I take the brush apart and try to fix it (and in fact probably
screw it up beyond repair)? Does anybody have a good address for a repair
point of contact at Testors? The Testors.com web site it most unhelpful
about repairs.
I spent about a half day trying to clean the brush with all sorts of
solvents and toothpicks and brushes to stop the problem and, I think, only
made it worse.
Thanks