Hi,
From TC5.1 onwards, the procedure is as follows (you can find this in the TC5.x release notes) :
EX60/EX90/SX20/C20:
When the unit is off, press and hold the power button
Wait until the power LED goes dark and then light up again (approximately 10 seconds).
Release the power button and press it twice.
The system will boot up and display a confirmation message on the video screen if the process was successful.
regards,