I have been going through many posts where many have said that they had bricked their tablet/epad etc... during ROM Update. It is now not even detected by USB in their PC. I would like to share a bit of the knowledge regarding unbricking such devices.
First of all, Please do not follow the Needle/Pin technique BLINDLY, mentioned in a few forums. It has some theorotical part to understand.
Starting with, this will be a two man job, so if you are attempting to unbrick, have one of your friend/brother/..., someone to help you.
1. Find a way to open the Device, so that you have access to the MainBoard inside. Opening a device may seem difficult at first, but try to google for the instructions of how to disassemble your device step by step. Do not open the Touch Screen side, because if there is mis-alignment with the touchscreen then the Touch response may not work partially or may be completely. We need access to the Mainboard only.
2. Find the Flash NAND device (CHIP) on the Motherboard. It usually is rectangular in shape. It has legs on only two sides (the smaller sides). Try to read the Make and Model number on that chip. Most commonly we find SAMSUNG NAND Flash present. For Eg: SAMAUNG Series K9GAG08U0F.
3. Now, Google for the datasheet of that NAND Device. If you are lucky you may get the datasheet. Else otherwise also no problem. Regarding the Legs/Pins on the Chip, there will be a notch on the Chip which specifies the Leg/Pin No. 1. The I/O Legs/Pins are located on the opposite side of Pin 0. (From hereon I refer Pins/Legs as Pins)
4. These I/O Pins will be 5th,6th,7th,8th number counting from both ends of the side which is opposite to that of the Notch. Refer the image attached.
5. Now confirm that the Tablet is in OFF state. Do not attach the USB Cable yet.
6. Open the Software Application in your PC which you are using to Update the ROM Image. Select the image file and be ready.
7. Take a screwdriver or any metal which has the edge width of 1mm or 1.5mm or so, and hold it shorting any 2 or 3 of the I/O pins with one hand (I mean I/O PINS ONLY). With the other hand, press and hold the Home/Esc button. Now you ask your partner to insert the USB Cable to the PC and connect it to your device. Instantly you can find that the PC has detected your USB device. Now you can let go the screw driver and the Home/Esc button slowly and install the drivers. Now the PC has detected your device and is ready to update the ROM. The rest updating part, i assume you are already aware.
PS: Before starting off, discharge yourself by holding any metal which is grounded. When holding the Mainboard do not touch the Components, Hold the Tablet at the Insulated Edges. You may have static charges on your body which may short the components and make your MainBoard of the Tablet UnRepairable.
A Partner would be extremely helpful in this process, because it may not be convenient to short the NAND Flash, Hold the Home/Esc button and Insert the cable -- All at the same time.
If anybody find this helpful, please donate me 25% of what you may be paying to your repair guy.