Hello Patrick, the chalk substance you see is just to keep parts from vibrating especially line filters and transformers, it is something Manufactures use to secure parts that will potentially vibrate and cause noise.
As to your no power issue there could be a few reasons, you could have a bad power/inverter board according to your picture the power board has to functions to power on the system and power on the LED lamps.
I don’t know your level of electronics troubleshooting, but the first thing you need to check is the supply voltages coming from the larger cable running to the Main board, the value of the voltages of each pin is indicated on the board in small print. But considering you have a red standby light on tells me your standby voltage is there. First try unplugging the TV and hold in the power button for 20 secs while the set is unplugged from AC. This is called hard reset. If that doesn’t work try turning on the set unplug the large cable coming for the power supply to the main board, the panel should light up if it does then replace the PS/Inverter board. The power supply supplies 5V constantly to the main board even when the tv is off. When u pushe power on button the main board sends 3.3Volts back to the power supply teling it turn on the rest of the unit. Also try disconnecting the Led connector at the top of the board this will be the smaller cable with wires running into the Panel and try turning on tv.
Hope this answer gives you some indication of where to start..
LT…