Ran "adb reboot bootloader" now can't boot past logo (Azpen A746) So I bought a cheap Azpen A746HD tablet to tinker with (running Android 4.4.2, I believe). This is my first time messing with an Android tablet, and it seems I've probably bricked it, but from what I can tell I didn't do anything "dangerous." I'm hoping for some insight from more experienced folks and any possible suggestions on how to get it to boot again.

I did not yet root the tablet (I was in the preliminary steps of figuring out how to do that). From what I can tell, what bricked it was simply running adb reboot bootloader. The current state of the device is as follows:


The device won't boot past the initial Azpen logo screen. Doesn't appear to be looping. Just stuck.
Pushing the device's "reset" button with a paperclip doesn't help. 
I can no longer boot to recovery mode (power + volume up) because it doesn't boot far enough to register the volume up button being pressed. 
The device no longer shows up with adb devices and it isn't listed in lsusb from my Linux terminal (it was showing up previously after I added the vendor id to ~/.android/adb_usb.ini). 
I've tried pressing the volume up/down button and power button in various combinations from the logo screen, with no result.


I don't have access to the battery, so I can't disconnect it. The device appears to be heat or glue sealed, so I can't disassemble it to access the battery (without making it unreturnable). Currently I am trying to fully drain the battery by leaving it powered on in its current state (stuck at logo screen).

Since I'm new to this, here are a few questions: Am I correct in understanding that this state a "hard-brick"? Why would adb reboot bootloader cause this? Is there anything more to try beyond the battery drain I'm currently doing? (I will just take back to the store and exchange if I can't get it booting again.)

FYI, the manufacturer's site is pretty much devoid of information, but what would you expect from a company that sells tablets for 30USD?
Fully draining the battery will unbrick an Azpen A746HD in this situation.

I did further testing and was able to repeat the conditions for bricking and unbricking the tablet:


Running adb reboot bootloader will render the tablet unbootable as described in the original question (hard-brick).
Fully draining the battery will clear out whatever issue was preventing boot, unbricking the tablet.