Case study: damaged read and write heads

When our data recovery laboratory receives a hard drive and it is determined necessary to purchase parts to complete a head swap to attempt the recovery of the data, our technicians perform a diagnostic, repair and retrieval procedure on the disk uising newly sourced parts.  In an attempt to recover the data and copy it to new media we often only get one attempt at data recovery.

The hard disk drive is disassembled in an ISO-4 standard clean air room so that it's internal components can be individually tested. The electronics PCB board, (which is responsible for all communication between the computer and the mechanical parts of the disk), is isolated and tested for damage to the fuse, transistors/capacitors, circuitry and interface. If all is found to be in working order, the disk is connected to an analysis machine and the ROM/firmware (a table of instructions found on the disk which allow computers to interpret the disks signals properly) is directly accessed and assessed. The magnetic plates (platters) are isolated and examined for signs of irreparable damage. If none can be seen on the accessible sides of the platters, the read/write heads (which span the magnetic platters and read the data) are isolated and examined. Often we see damage to the arm and magnetic reader; furthermore when power is supplied to the disk the read/write head(s) are found not to be positioned within the correct alignment. Additional tests on the motor are carried out (the component responsible for spinning the platters).

Damage to read/write heads is often caused by the misaligned positioning of the head assembly when the hard drive is not powered. In addition to this small pieces of dirt and dust are normally detected on the individual reader heads. The actuator arm and read/write heads are chemically cleaned and re-examined to maximize the chance of re-alignment. The arm is then mechanically altered to prevent further alignment problems and the read/write heads are re-assembled on to the disk. Sometimes, subsequent diagnostics confirm that the repairs are unsuccessful, but this only accounts for 10% of head crashes.

An identical hard disk is sourced and subsequently ordered and used for spare parts in order to attempt the recovery of the data. The read/write heads are completely removed from the newly ordered disk and are examined to ensure they are in working order. This second set of read/write heads are assembled into the original disk replacing the existing malfunctioned heads and carefully aligned.

Further analysis of the medias platter surface are carried out to ensure there are no inconsistencies of the magnetic properties which could potentially be linked to the contact made between the head and platter surface resulting from the initial ‘head crash’. Head crashes may be caused by one of several factors ranging from environmental impacts (e.g. a drop or bang) up to temperature expansion of certain components. The heads are then initialized long enough for a forensic scan to take place.