Screen stays black - built in battery

Dear all,

we are having trouble with a Toshiba satellite C70-C-1EN (found only a german website: http://www.toshiba.de/discontinued-produ...).

The problem: the screen stays black after turning the laptop on. After a while, the fan will start running and that's it. On any other laptop I would remove the battery, but this one is built in and I couldn't find any reset button either (one of the type where you have to stick in a paper clip).

The course of events that lead to the state of the laptop:

• Initially, the computer froze and was rebooted using the power on/off button.
• The computer then booted & started normally.
• After a while of using it, the bluescreen "DPC_watchdog_violation" appeared, a system check ran, finished at 100% but never rebooted automatically.
• The computer was then turned off and on again, now the problem is the black screen.

Here is what I have tried/thought about and some further information:

• I left the computer running, hoping the battery would be empty at some point - but the computer turns off before the battery is completely empty (the LED of the power button is still blinking).
• I do not have access to any external monitor, but I am quite certain that it is not booting normally and we just don't see. The keyboard has an LED in the caps lock which does not turn on when pressing caps lock. Also, the fan is running at full speed (which it didn't do in the past during regular booting).
• I understand that based on the symptoms there might be an issue with the motherboard. The laptop is still under warranty, but we are a few thousand kilometers away from the vendor. I would like to not give up the warranty by opening everything, but maybe someone has an idea if there is a way to do a hard power cycle in this tricky setting?

Thank you!