HTC Thunderbolt won't turn on
You hold the power button and nothing happens.
Battery is drained
If your Thunderbolt has not been used recently, or you have used it until it dies, your battery may be drained. You need to charge the Thunderbolt by plugging the charging adapter into the wall outlet and then plugging the cord into your Thunderbolt. Once plugged in, allow ten minutes for the phone to charge before attempting to turn it on.
Battery is dead
If your Thunderbolt does not turn on after plugging it in and allowing it to charge, you may have a dead battery. You will need to replace the battery.
If charging and replacing the battery did not allow your Thunderbolt to turn on, it is likely that you have a bad display and will need to replace it.
If all else fails, the last step is to replace the motherboard.
HTC Thunderbolt has no sound output
Your thunderbolt is working properly, however, when you try to play an audio source it does not work as expected.
Volume level is at zero
It is very likely that the volume level is turned off. With a source of audio playing, click the volume up button on the side of the Thunderbolt until the desired volume level is reached.
Speakers are broken
If turning the volume level up does not solve the problem, there may be an issue with the speakers that requires you to replace them.
HTC Thunderbolt's side buttons are unresponsive
While attempting to use the side buttons, such as the volume up and down buttons, nothing happens.
Phone is off
The first thing you should try is making sure the Thunderbolt is powered up by holding the power button for a few seconds.
Phone is locked
If the Thunderbolt is turned on and the side buttons are unresponsive, ensure that it is unlocked by clicking the lock/unlock button, and then enter your passcode. This should allow the side buttons to function properly.
Button is jammed
After making sure the Thunderbolt is powered on and unlocked, if you are still experiencing issues it is likely that the buttons are either jammed or sticky. The buttons will need to be replaced to fix this.
HTC Thunderbolt's power button is unresponsive
The power (lock/unlock) button does not respond as it should when clicked.
Phone is off
If the Thunderbolt is powered off, you must hold the power button for a few seconds for the phone to turn on.
Button is jammed
If the Thunderbolt is powered on and otherwise functioning appropriately, the power button may be jammed. To fix this the button must be replaced.
HTC Thunderbolt's screen is unresponsive
The phone is powered on but does not respond to touch input from the screen.
Screen is frozen
The most likely issue is that the Thunderbolt's software is frozen and needs to be restarted. Hold down the power button until a message appears on the screen and then tap "Restart". Once the Thunderbolt powers on it should be functioning as normal. If this did not work, you will need to remove the battery for a few minutes and then re-insert it by following these instructions.
Screen is damaged
If restarting the phone and removing the battery did not resolve the problem, your Thunderbolt may have a damaged screen. You will have to replace the screen to make it respond to touch input.