The HDMI port does not have a power pin, it's only for outputting video. The usb port is the only way to charge the 7G3, and you are going to have to send it in for service. Assuming it's under warranty, this should be covered. You will need to contact Archos/Arnova technical support via their phone number, have your device's info handy (model/serial #), where purchased etc. Arnova will ask you to email a jpeg picture of your store receipt to them (I've done this last year). When your RMA order is approved, mail it back using the printed out address label they will email to you in a suitable box (not the original packaging), wrap the tablet in protective bubble wrap. Make sure you remove your MicroSDCard! Arnova will most likely send you a new replacement tablet instead of repairing the old one, that's their option, sop.

  The usb port probably failed where it's soldered to the circuit board, I lost a garmin gps unit this way. It's a weak point in most any device, which is why I try my best to not stress or excessively wiggle the charging cable when it's plugged into the usb port.

  So, yep, sorry to say there's nothing you can really do except to send it in for repair/ replacement. Tell the tech department if you have any critical information stored on the tablet, they might be able to help with that, but assume that that data is most likely going to be lost. Expect it to take a month or two before you receive the repaired/ replaced tablet.

You're quite welcome Just thinking, I presume you've ruled out that it isn't the charger/ usb cable that might be the problem by using another, known to be working, micro-usb charging cable. The only other thing it could be is a bent/ broken pin in the tablet's usb port or cable. Good luck to you.