This TV had no standby voltage. Power supply board is RDENCA354WJQZ (DPS-208BPA). A badcaps post pointed to the potential of IC7905 TNY264PN being bad. This post indicates R7918 may need replacement. On my board, the IC blew up and broke on top but R7918 measured 2.4ohm which was ok.
I ordered a replacement IC on Ebay, installed it, but still got no power. Further research indicated R7914 may be blown which is a 2.2 ohm fusible resistor located under the bottom shield. I measured it, and it was open. Shopjimmy sells a repair kit for a similar power supply RDENCA336WJQZ (DPS-286AP) with a replacement IC7905, D7908, R7914 and R7918.
I ordered a replacement for R7914 (2.2 ohm, 1/2W fusible resistor Digikey #PPC2.2BCT-ND and D7908 (1N5383 Digikey #1N5383BRLGOSCT-ND). D7908 tested ok but I added it to the order since I had to pay shipping anyway. After installing the new resistor, the TV powered up.
I would also recommend updating the firmware. You can download the file from here. I was unable to download the instructions. You need to unzip and copy the .bin file onto a FAT USB flash drive (not FAT32) and plug it into the service USB port. There is a software update option in the setup menu. It should find it, and ask you if you want to proceed.