I seem to be getting at least two unsolicited questions a day from people who have inadvertently bricked their Eken M001/M002/M003 or Flytouch/noname tablets . So here's a quick post with what I know about unbricking.
You should also try slatedroid, and hassle whoever is making custom firmwares to remove the unnecessary bootloader reflash steps. These dangerous reflashes are what is causing so many tablets to brick in the first place.
Also, always plug your tablet in to the charger when flashing. Never unplug it or turn it off while it's flashing, even if you're accidentally flashing it twice. Seriously, people.
WM8505 tablets have a pre-bootloader called W-Load, then a bootloader called u-boot, then the main OS boots.
U-boot will read a custom boot script from a file "script/scriptcmd" on an SD card, if it is present. This is how upgrades and reflashes work. U-boot is also capable of interacting with the user via the built-in 3.3v serial port, if you solder some wires to it.
Stuck on the 'Android Logo' boot screen
This is the first screen, which also says "Kernel Version X.Y.Z" and "SDK Version X.Y.Z.". This screen is put up by u-boot.
If you're stuck on this screen then u-boot is loading, which is a good sign. If putting in an SD card with an upgrade script does not work, then it may be broken in some other way. You may be able to connect a serial cable and interact directly with u-boot to issue commands.
Before you bother with the serial cable, make very sure you have formatted your SD card correctly (FAT32) . Try reformatting and re-copying all the files to the SD card, and then try using a different SD card. Various people have reported that only SD cards 2Gb or smaller work reliably.
Stuck on the 'Android' "shimmer" boot screen
If you're stuck on the next boot screen (the text 'Android' that shimmers back and forth) then Android has started loading but is crashing. Reflash via the SD card.
If you have a totally blank screen then this is a much worse sign. In my experience, I've seen three possible things:
If the red power light blinks on when you press Power but then immediately goes out
Then you have a fault in your power circuit on the board. In my Eken, I can still make it boot if I take the back off and heat up the board with a heat gun (hair dryer would also work.)
If the red power light stays on and eventually you hear the 'ding' startup sound
(Instead of the 'ding', another sign is if you can connect it to your computer via USB.)
Then your Eken is working but your LCD panel is not. It might be broken, or it might be a bad connection. I've had luck pressing (lightly) around the edges of the screen.
If the red power light stays on but you don't eventually hear any 'ding' startup sound
Then your Eken is probably stuck either loading W-load or u-boot. There are some anecdotal reports that these boards will still take a normal SD card based update, so try some different firmwares via SD card as a first step.
If that doesn't work then you probably have a brick. The only way from here would be to reflash directly or via JTAG, and noone has found a JTAG pinout on these boards. You can connect the serial port to be 100% sure, but I wouldn't hold my breath.
EDIT: Ziann123 has posted a comment about unbricking via JTAG. Apparently he has a newer revision board, where the JTAG pinout is broken out and clearly labelled.
I have none of the above
If you have different symptoms, feel free to post in the comments. You'll probably get better responses by posting on slatedroid, though.