Oops is RIGHT!
-> What went wrong?:  I forgot to consider what I should have known!
-> That when the two sources were 180 degrees out of sync, the
-> voltage difference would be 240V! ( [+]120V - [-]120V ) -not the
-> usual 120V that I was erroneously expecting. Dang!
I did exactly the same thing Jim, 'cept I didn't do it with anything as
sensitive as an invertor.  I did it with the grid and my 6KW generator.
(Which didn't even quiver.)
I now have a pair of 6 watt bulbs permanently wired into an outlet box
with test leads attached.  
 ^..^
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