How do I find the polarity of my Braun Silk Epil adapter that is broken?

My Braun adapter 5497 with specs:

Input: 100-240V /ac
50-60Hz/ 7W
Output: 12V /dc
400mA

is broken I want to make a new one using the jack but I don't know the polarity.
Can anybody help me? If you have the same please do tell
Maven, October 2015


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