[Mark Dowsett]

I said I would report on the result of changing the external power supply for my unreliable LaCie drive. It’s entirely positive – the drive stays mounted – not a single problem in 4 weeks. So, the conclusion has to be that this fairly pricey unit which should be ultra reliable, has a nasty cheap power supply which lets it down.

[Mark Dowsett]

Well, what goes around, comes around. Its 2013 and still similar problems. My LaCie Big2 with Thunderbolt interface is a year old. Running off early 2011 17 in MBP through the Thunderbolt monitor. Rate of warnings about illegal unmounting of drive has increased over the last 6 months. Problem started with Lion, got worse (adventitiously) with Mountain Lion, seemed associated with sleep at first, then more random, but occasionally the drive also took a long time to mount from boot up (with big flashing blue light). Then, suddenly, it would not mount at all. A look at the power supply (hints earlier in this thread, thanks) showed that although it was still regulating at 12 V, the output impedance was way too high to deliver the 4 A needed to spin up the drives, but just enough to make the big blue light on the front flash on and off. The supply was also making a ticking sound. I replaced it with 12 V supply from RS (188-769, £24 in UK money) but I had to swap the connectors. Note, the supply needs to deliver at least 4 A and the centre pin on the connector is +ve. It’s now up and running, so I suspect that the supply has been failing intermittently, and not delivering the power needed to spin up the discs. So, if anyone else still encounters this type of problem, I recommend having the supply tested, not just for output volts, but to see if the voltage drops on load. I’ll let you know if the fix fails in the next few weeks …