Black screen

[xmack]

Hello i'm new here and new with jxd. Last week i bought this machine. 
I play with it about 30 minutes and it freezes. Then i tried to restart it and no JXD logo appears only black scree with green power led on.
I didn't try to upgrade or install another firmware only restart it.
USB didn't recognise it, i tried to install another firmware with a SD card starting with power on + volume up but nothing appears no JXD logo , no robot, nothing.
What can i do? Seller says that was because i brick it whith a bad try of changing firmware but it´s not true.
Excuse my english level. Thanks.

[doc]

Hmmm... sounds fishy. Who did you buy it from?

[xmack]

From ebay power seller

[doc]

Theres your first problem. For these types of devices I try to stay away from Ebay.

Here is a good topic to go through on bricking.
boards.dingoonity.org/jxd-devices/jxd-s7300-fixes-firmware-roms-thread/

Hope that helps.

-Doc