Interesting. I received two of these today, and I opened one up to look for promising diodes. I should have measured the voltages first .
Without any modifications I already measure +12 V on the barrel jack when the camera's running off of POE.
So maybe Amcrest dispensed with that diode and is using some other method to protect the power circuit. I don't have an illuminator at work, but I'll see if I have one lying around at home when I get home. Worst case I can plug into one of my existing POE drops and external illuminators and see if it lights up.