Two Seagates, One Mac, Neither Mounting

The decode

Two drives with the same symptom deserves one careful question before two separate diagnoses. Identical failures across two devices can be coincidence — or can point at something they share: the same Mac's USB port or software state, the same cable, the same power source. That possibility is checked first and cheaply, because if the Mac or a cable is misbehaving, the drives may be healthier than they appear. Ruling the shared factor in or out is the sensible opening move.

The missing light is the sharpest clue on the table. A drive that spins but shows no light has a power-delivery fault that reaches the indicator but not, or not fully, the rest — a failing bridge-board power stage, a connector problem. The mechanism running while the light is dark tells you power is arriving unevenly, which localises that drive's fault to its electronics rather than its platters.

Spinning-but-invisible on the first drive is a bridge or enumeration fault. The motor running means power and the drive's basic mechanics are working; the failure to appear in Disk Utility means the drive never completes the handshake that would present a volume. On portables that handshake runs through the USB bridge board, and a faulty bridge produces exactly this — a healthy-sounding drive the computer cannot see.

The Mac context adds a specific wrinkle worth naming. These drives hold Mac-formatted volumes — HFS+ or APFS — which mount on nothing but a Mac. That matters for recovery method: even once a drive's electronics are repaired, its filesystem has to be read with tools that understand Apple's formats, working from an image rather than by plugging the bare drive into any machine to hand.

Both faults are very likely electronic, which is good for the data. Bridge-board and connector problems threaten access, not the platters behind them. If the mechanisms are sound — and both drives spinning suggests they are — then repairing or bypassing the faulty bridges, imaging, and reading the Mac volumes should return the data on both. This is repair-and-image work, not surface recovery.

The honest split is stated per drive. Each is assessed and quoted on its own condition — two drives is two recoveries, though a shared cause discovered early could simplify both. If either turns out to have a mechanical fault beneath the electronic symptom, that changes its prognosis, and is reported before the work rather than after.

On the bench

Each drive was assessed independently on a bench power supply with current monitoring, the no-light unit checked first for a power-stage fault, and the shared Mac and cabling ruled out as a common cause. Bridge boards and connectors were examined under stereo microscope, and the drives removed to native SATA to separate bridge faults from drive faults. Both were imaged on DeepSpar Disk Imager with their original bridges retained, and the Mac-native volumes parsed from the images in UFS Explorer and extracted, hash-verified.

The outcome

Shared cause excluded, each drive repaired on its own electronic fault, both imaged and their Mac volumes read from the images. 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: two drives, one symptom, two stages of the same electronic fault — and the dark light on the second names a power problem. Both mechanisms run, so once the bridges are fixed the Mac volumes read and your data comes back.

Our case files are written up from genuine enquiries our lab has handled for customers across Sheffield and South Yorkshire, anonymised to protect client confidentiality. Each one describes the diagnostic and recovery approach our engineers apply to that fault, using the equipment listed.