Originally Posted by Chan Tran
Is it possible that the polarity of the Youngnuo trigger reversed?
I don't know the details of that trigger but it's easy to make the polarity irrelevant by fitting an opto-triac as is the case for the Pocket Wizard circuit in the patent Rudeofus linked to above.
"People who say things won't work are a dime a dozen. People who figure out how to make things work are worth a fortune" - Dave Rat.