I found this to be the case after working on a failed mod board. I was in the process of repairing traces and booted it many times without issue then suddenly without warning the box would suddenly not respond to power or eject buttons.
I found the collector to be producing unstable voltage of less than 3v. This confirmed the issue the board was having, I purchased some of the MMBT3906LT1 transistors and found replacing it resolved the power on issue.
To install I found a good set of tweezers essential for positioning it. For installation and an x-acto knife easies removal. With the tip of Gently pry up on the single conductor side, heat the side with the single conductor and bend it upwards then repeat on the other side with the dual contacts. Installing was fairly easy as well once it is properly positioned, solder the single contact at a low temperature and continue on to the side with dual contacts once positioned properly.