Here's what I've tried so far.
Starting with no USB devices attached.
Disconnecting the HDD,
Attempting to load an image from the front USB. (no other USB devices are attached)
Starting without the twin DVB-S2 and DVB-T tuner cards.
What makes it difficult is the box doesn't get to the stage where the prompt to update from the front USB appears. It used to boot with the VFD displaying CFE V2 and then "double your expectation" would appear followed by a message asking to press the power button for an update. There's no video on the screen and nothing appears on the VFD or LCD at all, possibly indicating that the basic functions of the receiver aren't starting. It behaves as if it's stuck in deep standby mode, the HDD spins up when it's connected but the fan doesn't spin.
The inside of the unit is immaculate with next to no dust. The white LED flickers when the front button is pressed, no response from the remote.