Video Assist 4K 12V power socket - which way is positive?

Hi
Newbie here. I have a Video Assist 4K without its original 12V power supply. I want to connect a third party power supply. Is the centre pin or the outer ring on the VA positive? I don't want to destroy it before I start!
Thanks.

Center positive.

Thanks, then I'm afraid that mine is not working. A very brief flash when I press the power button, then blackness. Same whether connected to a BMPCC by HDMI or not. Looks like a bad ebay purchase, unless you have any suggestions. I'll try with battery when I get back home.
Hugh

How many volts did you connect the VA to?
Cheers

Mine is 12 V, but max 17.2W. The CVP supply for it is 20W, so maybe mine is underrated. What power/current is the original BM power supply?
Thanks, Hugh

Yes, check with battery first. It should work from 12 volts up to like 20v, I forget the actual rating but it is somewhat wide.

Problem solved. Using proper batteries it all works fine. Moral (for newbies like me): don't assume that just because a power supply plugs into the wall it will provide enough current, even if the voltage is correct. Thanks, everyone.