Misaligned heads on a hard disk drive...

The data recovery laboratory received a hard drive with misaligned heads and it was determined necessary to purchase parts to complete a head swap to attempt the recovery of the data. Using the newly sourced parts, our technicians performed diagnostic, repair and retrieval procedures on the disk in an attempt to recover the data and copy it to the chosen media.

The hard disk drive was disassembled in an ISO-4 standard clean air room so that its internal components could be individually tested. The electronics PCB board, (which is responsible for all communication between the computer and the mechanical parts of the disk), was isolated and tested for damage to the fuse, transistors/capacitors, circuitry and interface and all were found to be in working order. The disk was 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) was directly accessed and found to be in working order. The magnetic plates (platters) were isolated and examined for signs of irreparable damage and none could be seen on the accessible sides of the platters. The read/write heads (which span the magnetic platters and read the data) were isolated and examined where damage to the arm and magnetic reader was revealed; furthermore when power was supplied to the disk the read/write head(s) were found not to be positioned within the correct alignment. However, additional tests on the motor (the component responsible for spinning the platters) found it to be in working order.

The damage to read/write heads was most probably caused by the misaligned positioning of the head assembly when the hard drive was not powered. In addition to this small pieces of dirt and dust were detected on the individual reader heads. The actuator arm and read/write heads were chemically cleaned and re-examined to maximize the chance of re-alignment. The arm was then mechanically altered to prevent further alignment problems and the read/write heads were re-assembled on to the disk. Unfortunately, subsequent diagnostics confirmed that the repairs made were unsuccessful.

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

Further analysis of the medias platter surface revealed 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’. This may have been caused by one of several factors ranging from environmental impacts (e.g. a drop or bang) up to temperature expansion of certain components. We were able to initialise the heads long enough for a forensic scan to take place, before further damage was caused to the replacement read/write heads. Thankfully we were able to recover 97% of the data. The 3% that was irretrievable related to system files only.