OK so just an update here. I plugged in a USB A to A cable to my computer to try get it to detect this box then I plugged in the power supply at the same time. I started getting that pulsing at the optical audio light onn the back the same as the way the multimeter measured the fluctuations. So then it just decides to stay on and the power light comes on. I got a burning smell so whatever caused the short must've melted. So even though it powers on I still can't get my PC to detect it and it doesn't show up when I plug in a HDMI cable. I'm gonna imagine whatever blew must be important and powers the internal emmc or something.

Anyway now that it powers up and gives me 5v and even 3.3v on the 3.3v line now, it should be a bit easier to diagnose.

 

I have problem with MXQ-4K Android Box.
We have before 4 day thunderstorm , and for moment box he stop to work .
Please , if a have somebody ides for this problem . write me .
Thank you very much for help .