Comment 5 for bug 515194

I didn’t know for sure if I should respond to this but it’s the only search result I could find.

I had this problem on a new build. The LCD would shut off and a few seconds later the backlight would come back on with no display.

For those that wind up here, it has nothing to do with the way Ubuntu configures it’s drivers. I spent a couple hours on this and using a multimeter discovered after the system halts the USB bus was being reset. As in, the power dropped to 0V for a second then back up to 5V. This resets the iMon display and causes the backlight to turn on with no display.

In the PC BIOS, I had enabled all wake options (from memory, Pcie, USB, lan, keyboard, mouse.)

It turns out enabling the machine to wake from a USB device causes the motherboard to reset all USB devices when the system halts so the attached USB devices can wake the system. On my motherboard, I only had to set the BIOS to wake from keyboard with any key and the iMon device will wake the system - all other options were disabled. After that, the iMon display shut off and stayed off when the system halted.

Hope this helps others.