No Signs of Life From a Hard Drive When Power is Applied

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By far the most common reason that a drive might appear totally lifeless when switched on (no sounds can be heard and no vibration is detected) is electrical damage to the printed circuit board (PCB), this is discussed in more detail in this article. However there is an alternative cause that also results in this behaviour in a significant minority of cases, that is the corruption of the portion of the hard drive’s firmware which is stored on the PCB.

What is a hard drive’s firmware? It’s a collection of information used by the drive to get itself up and running. It is essentially a set of instructions to the drive as to what specific parts it has at its disposal and how it should use them to start-up and present itself as a recognisable storage location to your computer. This information is typically split between two locations on your hard drive, a small portion on the PCB and the remainder on the platters inside the drive (alongside your data but in a reserved region of the platters which is inaccessible in normal operation). When power is first applied to a hard drive the processor chip (on the PCB) will read the firmware which is stored on the PCB, this essentially instructs the drive about the boot-up sequence and (critically) tells the drive where to find the rest of the firmware on the platters inside the drive.

Sometimes the PCB firmware is stored in a memory cache within the processor chip itself and sometimes it is in a separate external EPROM chip (a programmable chip). Either way, if this data is corrupted then the boot-up sequence doesn’t get a chance to complete and in all likelihood the drive will not even attempt to spin-up.

The red arrow indicates the EPROM chip holding the PCB firmware information.


In this case there is no external EPROM, the firmware information is held in the processor chip (blue arrow)


Now for one of data recovery’s more enduring misconceptions. Once this PCB firmware has become corrupted surely we can simply get another PCB from an exact-match hard drive of the same model and replace the original. As you will discover the answer is almost certainly not. Typically you will find that the drive now spins-up with the new PCB but that there is no access to the data (another common result of a simple PCB swap is that the drive will spin and you will hear the heads click repeatedly). While it is not possible to say categorically that such a straight PCB swap will not work, the chances of success are not high (in our experience, perhaps 1 in 20 such attempts will allow access to the data). There are many different reasons for this behaviour varying from manufacturer to manufacturer, as an example Hitachi hard drives vary the start location of the firmware on the platters, this address is of course stored in the PCB portion of the firmware in order that it can be located at start-up. Even drives of the same model and firmware version will almost certainly have different start locations for the data platter firmware. Hard drives also locate the “head-map” in the PCB firmware. For example many drives will have 4 heads fitted but only 3 are in use, knowing which 3 out of the 4 are used is of course vital for the hard drive to operate correctly.

The method of re-gaining access to hard drive data where the PCB firmware has been corrupted again varies between manufacturers, (it is worth noting that in some instances there is no solution). By way of an example, the more recent Western Digital can often allow access to the platter firmware (but not the user data) through the use of a closely-matching PCB, this in turn can then allow the original PCB firmware contents to be re-built. The user data can then be accessed normally again.

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