Data Recovery Case File · Desktop Externals & Aging Drives · Two Supplies, Two Answers
The Difference Between the Two Is the Finding
His enquiry contains an observation that most people would not think to make. An external drive after a minor fall: "when plugging in, the indicator doesn't light. There is no noise when plugging the power cord in, but when it is connected to the PC via USB there is a whirring noise, as normal." Two power sources, two different behaviours. That comparison is a real diagnostic and it costs nothing — because a drive that responds to one supply and not another is telling you where in its power path the fault sits.
| Media | External hard drive following a minor fall — no response on mains supply, rotation audible when connected via the host interface; activity indicator not illuminating |
| Reported situation | Drive subjected to a fall described as minor · activity indicator not illuminating · no audible response when the mains adapter alone is connected · rotation audible when connected to a computer over the data interface · no volume presented |
| Fault class | Power path fault between supply inputs — mains regulation stage implicated; mechanism confirmed capable of rotation |
| Equipment used | No further connection attempts · both supply inputs traced separately on a controlled bench supply · current draw measured on each path · enclosure board assessed at component level · drive assessed separately on a native connection |
The decode: what two supplies reveal
Why an external drive often has two power inputs: a mains adapter for the drive's own requirements, and power available over the data interface for the enclosure's electronics. Depending on the design, those feed different parts of the board through different regulation stages — so a fault can affect one path and leave the other working. That is why the comparison is informative.
What each of his observations establishes: rotation on the data connection proves the motor works, the bearing turns, and the drive can spin — which eliminates the entire family of faults where a mechanism cannot start. No response on the mains adapter means that path is not delivering, and the fault lies in the adapter itself, the socket, or the regulation stage it feeds.
Why the indicator not lighting fits: the activity light usually runs from the same circuitry as the mains path on a design of this kind. So a dead light and a dead mains response are frequently the same fault seen twice, rather than two problems.
Why the fall is probably relevant even though it was minor: a fall does not need to damage the drive to damage the board. A power socket takes the shock through its solder joints, a component can crack, and a board can flex enough to fracture a trace — all of which produce a dead power path on a mechanism that is entirely undamaged. "No big impact" and "the board took it" are perfectly compatible, and this is one of the cheaper faults an external drive can have.
Why that is genuinely good news: if the drive spins and the fault is in the enclosure's power stage, the data is sitting on a healthy drive behind a broken supply. Establishing that separates a component repair from a recovery, and the two have very different costs.
The test worth running generally, since it is free: where a device has more than one way of being powered, try each and note the difference. Most people plug in whatever is convenient, see nothing, and conclude the drive is dead. Reporting that it behaves differently on two supplies is worth more than reporting that it does not work.
What not to do: not keep swapping between supplies to see if it improves. If the regulation stage is faulty, repeated attempts risk delivering something the drive should not receive.
On the bench
No further connection attempts were made, a faulty regulation stage risking delivery of out-of-specification voltage on repeated tries. Both supply inputs were traced separately on a controlled bench supply with current draw measured on each path — the owner's observation of rotation on one supply and no response on the other localising the fault to a regulation stage rather than the mechanism, which is the distinction between a component repair and a recovery. The enclosure board was assessed at component level, and the drive assessed separately on a native connection.
The outcome
Both power paths traced separately, the fault localised to the enclosure's supply and the drive assessed independently. Free assessment, one fixed written figure including VAT; where a drive has to be opened, 50% of parts and labour is payable upfront with the balance only on success — otherwise no recovery, no fee. The decode: a drive with two power inputs feeds different parts of its board through different regulation stages, so a fault can kill one path and leave the other working. Rotation on one supply proves the motor and bearing are fine. And a fall does not need to reach the drive to break a socket joint or fracture a trace.
Drive that behaves differently on different power sources
Note the difference and report it — that comparison is a real diagnostic and hardly anyone thinks to make it. External drives often have two power inputs, a mains adapter and power over the data connection, and depending on the design those feed different parts of the board through different regulation stages. So a fault can kill one path while the other still works. If your drive spins on one supply and does nothing on the other, that already proves the motor and bearing are fine and places the fault in the enclosure's power circuitry rather than the drive. A minor fall doesn't have to reach the drive to do that — a socket joint or a fractured trace is enough. Don't keep swapping supplies to see if it improves.
That's useful information — call Guildford Data Recovery on 01483 901310; both inputs traced on a controlled bench supply, draw measured per path, board assessed at component level.
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Our case files are drawn from genuine enquiries received by our laboratory over the past ten years, anonymised to protect client confidentiality. Each one describes the diagnostic and recovery procedure our engineers apply to that fault, using the equipment listed.