Hard Drive Repair - PCB

硬盘爱好者

  Attempts to repair mechanical failures by anyone other than a qualified data recovery shop or the manufacturer, will void the warranty.

Swap at your own risk!
There is a certain amount of agreement, between several of the data recovery service companies, that replacing the PCB, on newer hard disk drives, is a bad idea. In fact, swapping the PCB may actually damage the drive further. They make a good case, have cited examples, and some have gone to great lengths to document their information.

Hard drive customization. At first glance the thought of each and every hard disk drive manufactured being customized, just sounds impractical. Writing variable data to each and every drive? Well apparently they do. If one stops and considers how easy it is and the benefits to the manufacturer's, even the most lay-person will agree.

The variable information is located in some key locations. One such location is the disk itself. There are tracks written to the drive that the average user cannot access. These are known as maintenance tracks. Another location is the EPROM on the PCB. After the mechanical portion of the drive is married to a PCB, during the manufacturing process, the drives are connected to a machine. This machine executes testing, burn-in, writing data to the maintenance tracks and EPROM. Technically, each and every ESDI, SCSI, ATA and SATA drive produced has been customized. The manufacturer's have always stored media defect information in the maintenance tracks. Defects are unique to each drive. So it's not a big stretch to further customize each one. The manufacturer's can reduce their failure rate by tuning the customized information for the thermal and mechanical characteristics of each drive. With the ability to tune each drive made, they can also increase capacity by stabilizing these factors during the manufacturing process.

So how does that affect swapping the PCB? If each drive can vary slightly in it's operating temperature and some of the mechanical properties can be adjusted to compensate. It's not too far from the realm of possibility to introduce a "matched" PCB to a Head Disk Assembly (HDA) that is so different, the PCB could actually do damage to the HDA. One data recovery shop reports there are models of drives on the market where swapping a "matched" PCB to a failed unit's HDA, destroys the swapped PCB.

Consider a serialization scenario. A PCB can be serialized to work with a particular HDA only. That's not too hard. Just write the serial number to the EPROM and the maintenance tracks. During the start-up sequence require the two serial numbers to match. If it doesn't match, it doesn't work.

The future of drive customization is on the horizon. Some reports suggest that the manufacturer's are leaning towards drive level security. The critical information written to the maintenance tracks and the ERPOM, in theory, would be encrypted. That certainly won't make things easier for the board swapper or the data recovery shops.

Is there a "line" where a PCB shouldn't be swapped? The introduction of highly customized information written to hard drives (believe it or not) occurred, to some degree, at the 5MB level (that's 5 megabytes!). With each new generation of disk drive thereafter the customization becomes more intense. In general, the larger the drive the less successful swapping the PCB becomes as a repair solution. The actual destruction factor seems to be limited to particular models at the 20GB level and above. However, I do not have sufficient information to identify them.

I can no longer, in good conscience, recommend swapping PCB's as a repair solution. Do so at your own risk. If you insist on doing so anyway, please use the following guidelines;

For the purpose of hard drive data recovery, the easiest way to get replacement parts and repair your hard drive is to buy another one just like it. Exactly like! Down to the revision!! Including the board!!! That said, the easiest way to repair an electronic problem is to replace the PCB on the drive. There are other electronic components in the drive. But, we'd have to void the warranty and they require special tools to replace. Simply swap the boards from an identical drive? Make sure it's the exact same board! Don't assume it's the same because the model number is the same, or close. Using the wrong board could start a fire!

Swap the boards and see if the symptoms change.

If the symptoms improve to the extent that the drive is recognized by the computer BIOS or SCSI HBA, image the drive now. If the symptoms don't improve, the problem is beyond any help we could provide here. You need professional assistance.

scott

Actually it's not that scary as the article stated. Just remember, before swapping the PCBs, make sure your hard drive is having a PCB problem, and double check that your new PCB is suitable for your hard drive body: check the part no. on the white lable as well as on the green board. And check the FW version of both hard drives. When they fail to match, but are using the same main control chip, do the rom/ram switching. And please be careful, if the hard drive clicks upon spinning up, cut the power ASAP.