I happened across a power supply that closely matches the one that came with the Rock Pi, but no change. I can rule out a power issue. I have Debian on both the eMMC as well as the SD card. At the time this happen, the SD card was not installed, so I know it it not corrupted. I tried booting with both the eMMC and SD card with no results. I removed the eMMC and tried booting from the SD card and nothing. I then tried booting up without either installed, expected to see the error telling me to install a boot drive, but didn’t get that either. I thought it might be the Hdmi cable, so I connected a blu-ray player and got a picture, so it’s not that.
I followed Brian’s instructions twice, first from the SD card and then, with the SD card removed, from the eMMC. The second time I added the “default kernel…” to extlinux.conf, but also typed “sync” and “reboot” from the console, thinking that maybe he meant those as commands. When I typed “reboot”, the screen went black and that was the end of the Rock Pi.
Clearly I did something wrong. I have no idea what, nor do I know how I could have corrupted the board. I could see corrupting the installations, but this seems to go beyond that. The hardware is corrupted.