Yep, you were right, everything is there, and it was a simple problem.

I read in the empeg documentation that the power could be between 8 and 16Vdc. My power source was giving 10.5Vdc, but it seems that it wasn't enough. I tried the laptop's AC adapter (16Vdc) and it worked, or at least it booted up. Now, is giving me a "No disk..." problem, but I suppose it is because I fiddled about with the IDE cable and it might have gone loose.

I actually see now that one of the symptoms I had ("Pump error" when upgrading the firmware) is described in the FAQ.

I guess it was going into standby mode (flashing light, display off...) automatically because it couldn't boot up, it didn't have the power to spin the drive up.

That's all folks!! (for now...)
Thank you.