Holding the button down will not work for some, but not all TVs. Some TVs require q 'pulsed' on switch, one that is pressed then released. For some TVs, you have apply mains power and then wait a second or two before pressing the power button to turn it on.
Peale's cap trick might work for some TVs, but bear in mind that Peale designed the trick for PCs, not TVs, and the voltages etc may be different from TV to TV. So use with caution & open mind.
There is no one solution for all TVs. In one case I just gave up and extended the power switch to a separate power button I installed, which was discreet but accessible from the outside of the cab. Now I'm really happy with that arrangement because it makes it easy to turn the TV off, but leave your game paused etc.