“Destroying Myths” - this section is dedicated to the most common myths that have taken root in the world information technologies. The editors of the CHIP test laboratory will help you distinguish fiction from the truth.
Many people believe that if a regular magnet is placed near a computer or hard drive, it will lead to data loss.
Is it true.
This opinion spread when 5.25- and 3.5-inch floppy disks were widely used. The magnets really shouldn’t have been brought too close to these data carriers: even a distance of three centimeters was enough to destroy all the data. However, even neodymium magnets with a powerful magnetic field do not pose any danger to hard drives. Modern hard drives with a capacity of 1 TB or more consist of two to four plates coated with a magnetic layer based on iron oxide and cobalt. Information on the platters is located in small areas (domains) of the disk, which can have two states of magnetization - 0 or 1. Bits of information on modern HDDs are stored in vertical domains. This method, called perpendicular recording, allows you to store up to 19 GB of information on one square centimeter.
Magnetic fields Reading and writing data to the HDD is carried out by moving the head above the platter at a distance of only 10 nm. This element works as an electromagnet and creates a strong field, under the influence of which domains are magnetized.
Thus, it is magnetic fields that allow information to be written or erased in domains.
But why then does an ordinary magnet pose no danger? The fact is that the plates are so strongly magnetized that only very powerful fields with an induction of over 0.5 Tesla can negatively affect the operation of the HDD. Since the strength of the magnetic field decreases with distance from the object, already at a distance of a few millimeters it will drop to a negligible value. Therefore, magnets brought to the HDD are too weak to affect the information stored on the hard drive.
Even a neodymium magnet with an adhesive force of 200 kg at a distance of 10 mm from an object creates a field with a magnetic induction of only 0.3 Tesla. However, be aware that if a magnet is placed near a running hard drive, it may tilt the read/write head to the side or cause it to touch the platter. This is fraught with recording errors and, as a result, data loss.
To date, probably only the deaf have not heard about neodymium magnets. They are made from an alloy - NdFeB, which has remarkable magnetic properties (it is not only powerfully magnetite, but also very resistant to demagnetization). It is not difficult to buy neodymium magnets in Moscow, but they can bring a lot of benefits in the household. Let's consider several non-trivial ways to use such magnets in the household. So,
The simplest and most fun are toys and puzzles. For this, rather weak small magnets are used, usually in the form of balls. Various complex shapes and sculptures are assembled from them. But do not forget that such magnets should NEVER be given to children under 4 years of age! A swallowed pair of such magnets, pinching the wall of the intestines or stomach, can easily cause its perforation with all the consequences.
Neodymium magnets are excellently used as clamps. In principle, a pair of medium magnets is quite capable of replacing a bench vise. However, it is more convenient to use magnets, since they can be used to fix parts of complex shapes. 
Motorists will probably be interested in using neodymium magnets as an oil filter. If you hang it on the engine crankcase drain plug, it will trap all metal inclusions in this place, which will then be easy to remove. 
Due to their strength, such magnets can be successfully used in search activities. For example, finding a fallen needle in a carpet, or a machine gun from the times of the Great Patriotic War in a river. Patriotic War(special search magnets with an eye for a rope are sold for this purpose). Can also be used to search for reinforcement in walls. 
Magnets have been used by magicians for a long time to create the illusion of levitation. With the advent of neodymium, such tricks reached a new level. 
You can also successfully magnetize various steel objects (screwdrivers, bits, tweezers, needles, etc.) with such a magnet. They can even re-magnetize a demagnetized ordinary magnet. 
Fixing inventory and tools. Special holders with magnetic properties will help you in proper planning of your workspace. 
Dent repair, from body repair to wind instrument repair. 
To delete data from magnetic media (hard drives, audio and video cassettes, credit cards). A powerful magnetic field perfectly removes all information. Quickly and without additional effort. 
In general, neodymium magnets are simply an indispensable assistant in the household. Only when working with them, especially powerful ones, strictly follow safety precautions. If a finger or other part of the body gets caught between magnetic objects (I already wrote about children), this could end very badly. 
Take care of yourself!
Based on materials from: http://neo-magnets.ru/
What does a modern hard drive (HDD) look like inside? How to take it apart? What are the parts called and what functions do they perform in the general information storage mechanism? Answers to these and other questions can be found here below. In addition, we will show the connection between Russian and English terminologies describing the components hard drives.
For clarity, let's look at the 3.5-inch SATA drive. This will be a completely new Seagate ST31000333AS terabyte. Let's examine our guinea pig.
The green plate secured with screws with a visible trace pattern, power and SATA connectors is called an electronics board or control board (Printed Circuit Board, PCB). She performs the functions electronic control work hard drive. Its work can be compared to putting digital data into magnetic fingerprints and recognizing it back on demand. For example, like a diligent scribe with texts on paper. The black aluminum case and its contents are called the Head and Disk Assembly (HDA). Among specialists, it is customary to call it a “can.” The case itself without contents is also called a hermetic block (base).
Now let's remove the printed circuit board (you'll need a T-6 star screwdriver) and examine the components placed on it.
The first thing that catches your eye is the large chip located in the middle - the System On Chip (SOC). There are two major components in it:
- The central processor that performs all calculations (Central Processor Unit, CPU). The processor has input/output ports (IO ports) to control other components located on printed circuit board, and data transfer via SATA interface.
- Read/write channel – a device that converts incoming data from the heads analog signal into digital data during a read operation and encoding the digital data into an analog signal during a write operation. It also monitors the positioning of the heads. In other words, it creates magnetic images when writing and recognizes them when reading.
The memory chip is a regular DDR SDRAM memory. The amount of memory determines the size of the hard drive cache. This PCB has Samsung memory DDR with a capacity of 32 MB, which in theory gives the disk a cache of 32 MB (and this is exactly the volume given in technical characteristics ah hard drive), but this is not entirely true. The fact is that memory is logically divided into buffer memory(cache) and firmware memory. The processor requires a certain amount of memory to load firmware modules. As far as we know, only the HGST manufacturer indicates the actual cache size in the technical specifications description; Regarding other disks, we can only guess about the actual cache size. In the ATA specification, the drafters did not expand the limit set in earlier versions, equal to 16 megabytes. Therefore, programs cannot display a volume greater than the maximum.
The next chip is a spindle motor and voice coil control controller that moves the head unit (Voice Coil Motor and Spindle Motor controller, VCM&SM controller). In the jargon of specialists, this is a “twist”. In addition, this chip controls secondary power supplies located on the board, which power the processor and the preamplifier-switch chip (preamplifier, preamp), located in the HDA. This is the main energy consumer on the printed circuit board. It controls the rotation of the spindle and the movement of the heads. Also, when the power is turned off, it switches the stopping engine to generation mode and supplies the resulting energy to the voice coil for smooth parking of the magnetic heads. The VCM controller core can operate even at temperatures of 100°C.
Part of the disk control program (firmware) is stored in flash memory (indicated in the figure: Flash). When power is applied to the disk, the microcontroller first loads a small boot ROM inside itself, and then rewrites the contents of the flash chip into memory and begins executing code from RAM. Without correctly loaded code, the disk will not even want to start the engine. If there is no flash chip on the board, it means it is built into the microcontroller. On modern discs (from about 2004 and newer, but the exception is hard disks Samsung and they with stickers from Seagate) flash memory contains tables with codes for settings of mechanics and heads, which are unique to a given HDA and will not fit another. Therefore, the “switch controller” operation always ends either with the disk being “not detected in the BIOS” or determined by the factory internal name, but still does not provide access to data. For the Seagate 7200.11 drive in question, the loss of the original contents of the flash memory leads to a complete loss of access to information, since it will not be possible to select or guess the settings (in any case, such a technique is not known to the author).
On the R.Lab YouTube channel there are several examples of rearranging a board with re-soldering a microcircuit from a faulty board to a working one:
PC-3000 HDD Toshiba MK2555GSX PCB change
PC-3000 HDD Samsung HD103SJ PCB change
The shock sensor reacts to shaking that is dangerous for the disk and sends a signal about it to the VCM controller. The VCM immediately parks the heads and can stop the disk from spinning. In theory, this mechanism should protect the disc from further damage, but in practice it does not work, so do not drop the discs. Even if you fall, the spindle motor may jam, but more on that later. On some disks, the vibration sensor is highly sensitive, responding to the slightest mechanical vibrations. The data received from the sensor allows the VCM controller to correct the movement of the heads. In addition to the main one, such disks have two additional vibration sensors installed. On our board, additional sensors are not soldered, but there are places for them - indicated in the figure as “Vibration sensor”.
The board has another protective device - a transient voltage suppression (TVS). It protects the board from power surges. During a power surge, the TVS burns out, creating short circuit to the ground. This board has two TVS, 5 and 12 volts.
The electronics for older drives were less integrated, with each function divided into one or more chips.
Now let's look at the HDA.
Under the board there are contacts for the motor and heads. In addition, there is a small, almost invisible hole on the disk body (breath hole). It serves to equalize pressure. Many people believe that there is a vacuum inside the hard drive. Actually this is not true. Air is needed for the heads to take off aerodynamically above the surface. This hole allows the disc to equalize the pressure inside and outside the containment area. On the inside, this hole is covered with a breath filter, which traps dust and moisture particles.
Now let's take a look inside the containment zone. Remove the disk cover.
The lid itself is nothing interesting. It's just a steel plate with a rubber gasket to keep out dust. Finally, let's look at the filling of the containment zone.
Information is stored on disks, also called "platters", magnetic surfaces or plates. Data is recorded on both sides. But sometimes on one side the head is not installed, or the head is physically present, but is disabled at the factory. In the photo you can see the top plate corresponding to the head with the highest number. The plates are made of polished aluminum or glass and are coated with several layers of different compositions, including a ferromagnetic substance on which the data is actually stored. Between the plates, as well as above the top of them, we see special inserts called dividers or separators. They are needed to equalize air flows and reduce acoustic noise. As a rule, they are made of aluminum or plastic. Aluminum separators cope more successfully with cooling the air inside the containment zone. Below is an example of a model for the passage of air flow inside a hermetic unit.
Side view of the plates and separators.
Read-write heads (heads) are installed at the ends of the brackets of the magnetic head unit, or HSA (Head Stack Assembly, HSA). The parking zone is the area where the heads of a healthy disk should be if the spindle is stopped. For this disk, the parking zone is located closer to the spindle, as can be seen in the photo.
On some drives, parking is carried out on special plastic parking areas located outside the plates.
Parking pad for Western Digital 3.5” drive
In the case of parking the heads inside the plates, a special tool is needed to remove the block of magnetic heads; without it, it is very difficult to remove the BMG without damage. For external parking, you can insert plastic tubes of suitable size between the heads and remove the block. Although, there are also pullers for this case, but they are of a simpler design.
The hard drive is a precision positioning mechanism, and for its normal operation very clean air is required. During use, microscopic particles of metal and grease can form inside the hard drive. To immediately clean the air inside the disc, there is a recirculation filter. This is a high-tech device that constantly collects and traps tiny particles. The filter is located in the path of air flows created by the rotation of the plates
Now let's remove the top magnet and see what's hidden underneath.
Hard drives use very powerful neodymium magnets. These magnets are so powerful that they can lift up to 1,300 times their own weight. So you should not put your finger between the magnet and metal or another magnet - the blow will be very sensitive. This photo shows the BMG limiters. Their task is to limit the movement of the heads, leaving them on the surface of the plates. BMG limiters different models are designed differently, but there are always two of them, they are used on all modern hard drives. On our drive, the second limiter is located on the bottom magnet.
Here's what you can see there.
We also see here a voice coil, which is part of the magnetic head unit. The coil and magnets form the VCM drive (Voice Coil Motor, VCM). The drive and the block of magnetic heads form a positioner (actuator) - a device that moves the heads.
The black plastic part with a complex shape is called an actuator latch. It comes in two types: magnetic and air lock. Magnetic works like a simple magnetic latch. Release is carried out by applying an electrical impulse. The air latch releases the BMG after the spindle motor reaches enough speed for the air pressure to move the latch out of the path of the voice coil. The retainer protects the heads from flying out into the work area. If for some reason the latch fails to perform its function (the disk was dropped or hit while it was on), then the heads will stick to the surface. For 3.5“ disks, subsequent activation will simply tear off the heads due to the higher motor power. But the 2.5" has less motor power and the chances of recovering data by freeing the original heads from captivity are quite high.
Now let's remove the magnetic head block.
The precision and smooth movement of the BMG is supported by a precision bearing. The largest part of the BMG, made of aluminum alloy, is usually called a bracket or rocker arm (arm). At the end of the rocker arm there are heads on a spring suspension (Heads Gimbal Assembly, HGA). Usually the heads and rocker arms themselves are supplied different manufacturers. A flexible cable (Flexible Printed Circuit, FPC) goes to the pad that connects to the control board.
Let's take a closer look at the components of the BMG.
A coil connected to a cable.
Bearing.
The following photo shows the BMG contacts.
The gasket ensures the tightness of the connection. Thus, air can only enter the unit with discs and heads through the pressure equalization hole. This disc has contacts coated with a thin layer of gold to prevent oxidation. But on the electronics board side, oxidation often happens, which leads to HDD malfunction. You can remove oxidation from the contacts with an eraser.
This is a classic rocker design.
The small black parts at the ends of the spring hangers are called sliders. Many sources indicate that sliders and heads are the same thing. In fact, the slider helps to read and write information by raising the head above the surface of the magnetic disks. On modern hard drives, the heads move at a distance of 5-10 nanometers from the surface. For comparison, a human hair has a diameter of about 25,000 nanometers. If any particle gets under the slider, this can lead to overheating of the heads due to friction and their failure, which is why cleanliness of the air inside the containment area is so important. Dust can also cause scratches. From them new dust particles are formed, but now magnetic, which stick to the magnetic disk and cause new scratches. This leads to the disc quickly becoming scratched or, in the jargon, “sawed.” In this state, neither the thin magnetic layer nor the magnetic heads work anymore, and the hard drive knocks (click of death).
The read and write head elements themselves are located at the end of the slider. They are so small that they can only be seen with a good microscope. Below is an example of a photograph (on the right) through a microscope and a schematic representation (on the left) of the relative position of the writing and reading elements of the head.
Let's take a closer look at the surface of the slider.
As you can see, the surface of the slider is not flat, it has aerodynamic grooves. They help stabilize the slider's flight altitude. The air under the slider forms an air cushion (Air Bearing Surface, ABS). The air cushion maintains the flight of the slider almost parallel to the surface of the pancake.
Here's another image of the slider.
The head contacts are clearly visible here.
This is another important part of the BMG that has not yet been discussed. It is called a preamplifier (preamp). A preamplifier is a chip that controls the heads and amplifies the signal coming to or from them.
The preamplifier is placed directly in the BMG for a very simple reason - the signal coming from the heads is very weak. On modern drives it has a frequency of more than 1 GHz. If you move the preamplifier outside the hermetic zone, such a weak signal will be greatly attenuated on the way to the control board. It is impossible to install the amplifier directly on the head, since it heats up significantly during operation, which makes it impossible for a semiconductor amplifier to work; vacuum tube amplifiers of such small sizes have not yet been invented.
There are more tracks leading from the preamp to the heads (on the right) than to the containment area (on the left). The fact is that a hard drive cannot simultaneously work with more than one head (a pair of writing and reading elements). The hard drive sends signals to the preamplifier, and it selects the head to which to this moment the hard drive is accessing.
Enough about the heads, let's disassemble the disk further. Remove the upper separator.
This is what he looks like.
In the next photo you see the containment area with the top separator and head block removed.
The lower magnet became visible.
Now the clamping ring (platters clamp).
This ring holds the block of plates together, preventing them from moving relative to each other.
Pancakes are strung on a spindle hub.
Now that nothing is holding the pancakes, remove the top pancake. That's what's underneath.
Now it’s clear how space for the heads is created – there are spacer rings between the pancakes. The photo shows the second pancake and the second separator.
The spacer ring is a high-precision part made of a non-magnetic alloy or polymers. Let's take it off.
Let's take everything else out of the disk to inspect the bottom of the hermetic block.
This is what the pressure equalization hole looks like. It is located directly under the air filter. Let's take a closer look at the filter.
Since the air coming from outside necessarily contains dust, the filter has several layers. It is much thicker than the circulation filter. Sometimes it contains silica gel particles to combat air humidity. However, if the hard drive is placed in water, it will get inside through the filter! And this does not mean at all that the water that gets inside will be clean. Salts crystallize on magnetic surfaces and sandpaper instead of plates is provided.
A little more about the spindle motor. Its design is shown schematically in the figure.
A permanent magnet is fixed inside the spindle hub. The stator windings, changing the magnetic field, cause the rotor to rotate.
Motors come in two types, with ball bearings and with hydrodynamic bearings (Fluid Dynamic Bearing, FDB). Ballpoints stopped being used more than 10 years ago. This is due to the fact that their beat is high. In a hydrodynamic bearing, the runout is much lower and it operates much quieter. But there are also a couple of disadvantages. Firstly, it may jam. This phenomenon did not happen with ball ones. If the ball bearings failed, they began to make loud noise, but the information was readable, at least slowly. Now, in the case of a bearing wedge, you need to use a special tool to remove all the disks and install them on a working spindle motor. The operation is very complex and rarely leads to successful data recovery. A wedge can arise from a sudden change in position due to of great importance Coriolis force acting on the axis and leading to its bending. For example, there are external 3.5” drives in a box. The box was standing vertically, it touched it and fell horizontally. It would seem that he didn’t fly far?! But no - the engine is wedged, and no information can be obtained.
Secondly, lubricant can leak out of a hydrodynamic bearing (it is liquid, there is quite a lot of it, unlike the gel lubricant used in ball bearings) and get onto the magnetic plates. To prevent lubricant from getting on magnetic surfaces, use lubricant with particles that have magnetic properties and capture their magnetic traps. They also use an absorption ring around the site of a possible leak. Overheating of the disc contributes to leakage, so it is important to monitor temperature conditions operation.
The connection between Russian and English terminology was clarified by Leonid Vorzhev.
Update 2018, Sergey Yatsenko
Reproduction or quotation is permitted provided that reference to the original is maintained.
HDD hard drives As an important and familiar carrier of information, it has one unpleasant property: it is short-lived. And after failure it is completely useless. Most often, it ends up in the trash heap, or is deliberately scrapped for recycling, which in our country is considered completely meaningless for a number of reasons, but the main one is the lack of a clear and widespread mechanism for recycling and separate waste collection. This is a topic for a separate discussion, perhaps we will return to it. In the meantime, we are finding uses in everyday life, because taking something apart is always interesting for an inquisitive mind! You can show your children the device modern drives and have an “interesting” time.
How can we benefit from a non-functioning drive? The only use that came to my mind was to get neodymium magnets out of it, which are known for their magnetizing strength and high resistance to demagnetization.
The process of disassembling and removing magnets.
If you have a tool, this is not at all difficult to do, especially since the disk is ready to fulfill its final purpose.
We will need:
- Six-pointed star screwdriver (T6, T7...depending on model).
- A thin flathead screwdriver or a strong knife.
- Pliers.
I have HDD WD 3.5 inches, which faithfully served me for 4 years.
We unscrew the screws around the perimeter, but the casing will not open just like that; there is another one hidden under the sticker. Apparently, this is a seal that is quite difficult to find. The hidden screw is located on the axis of the magnetic heads (in the photo I marked it with a red circle), in this area there is a hidden fastener. But we don’t have to stand on ceremony, because we only need magnets, the rest has no value. You should end up with something similar, one or two metal plates with magnets. Using pliers and some force, bend the metal plate and carefully pry up the magnets. I was lucky, the plate turned out to be flat, and I glued it to the shelf on the desktop with super glue. The tool is at hand, does not hang around the table, and most importantly, we have given a second life to some part of the hard drive. I think everyone will find a use for magnets in everyday life.
Not everything is in the photo! Only those that I “sentenced” when I conceived this homemade product!
Some are out of order. Others are simply outdated. (By the way, it can be traced The general trend Reduced quality: modern hard drives fail quite often. The old ones, one or two gigabytes (or even much less), are all working!!! But they can no longer be used - they have a very low speed of reading information... And they have very little memory. So it's not worth it.
But you can’t even raise your hand to throw it away! And I often wondered what could be made from them, or how to use them...
On the Internet, at the request “...from the hard drive” there are mainly “super-talented” ideas for creating a sharpener!!! People with a serious look show how to trim the case, cover the disk itself with sandpaper, and make a super-cool sharpener, powering it from a computer power supply, and using the hard drive’s own motor!
I haven’t tried it... But I think it will be possible to sharpen with such a sharpener... well, maybe nails!... And even then, if you don’t press too hard!!
And now, when I was doing this, I remembered that hard drives have powerful neodymium magnets. And since during welding work “there can never be too many squares,” then, after completing the last homemade project, I immediately disassembled one of the hard drives to see what I could operate with)))
The magnet (I pointed to it with a red arrow) is glued to a metal bracket, which, in turn, is secured with a screw.
Old hard drives had one or more massive magnet. There are two of them in the new ones. The second one is below:
This is what I got when I disassembled my disks:
By the way, the discs themselves also interested me. If anyone has ideas for using them, please share them in the comments...
To begin with, I decided to search the Internet to see if anyone had already invented this method of making welding angles?!)))
It turned out yes! We've already made these devices from hard drives! But there the man simply placed a wooden board between the metal plates, to which he screwed magnets. I immediately rejected this method for several reasons:
Firstly, the combination of “arc welding + wood” is not very good!
Secondly, at the ends of these squares a rather complex shape is obtained. And it will be very difficult to clean them! And he will take on a lot. Let me give you an example of a photo from my last publication. They have a weak magnet on them, and this one, after lying on the workbench where they worked with metal:
And thirdly, I didn’t like that the square had very wide ends. That is, when welding some structures whose components are narrower than itself, it cannot be used.
Therefore, I decided to go a different route. Make, like the “wooden” one, not the template plates of the case, but the end itself between them, but make this end smooth and closed.
In a previous publication, I already wrote that all magnets have poles, which, as a rule, for permanent magnets are located on wide planes. It is not advisable to “close” these poles with magnetic material, so this time I decided to make the side plates of the case from a non-magnetic material, and the end plate from a magnetic one! That is, “exactly the opposite”)))
So what I needed:
1. Neodymium magnets from old computer hard drives.
2. Non-magnetic stainless steel plate (for the housing).
3. Thin magnetic steel.
4. Blind rivets.
First of all, I started making the case. I had this piece of stainless steel sheet. (I don’t know the brand, but steel does not stick to a magnet).
Using a plumber's square, I measured and cut out two right triangles with a grinder:
I also cut the corners of them (I forgot to take a photo of this process). Why cut the corners, I already said - so as not to interfere with welding work.
I made the precise adjustment of the corners manually on a piece of emery cloth spread along the plane of a wide profile pipe:
Periodically, I put the workpieces into the square and looked “through the light.” After the corners were out, I drilled holes for the rivets, connected the plates through them with M5 screws, and checked the corners again! (The requirements for accuracy here are very high, and when drilling holes, I could make an error).
Next, I started making the magnetic plate itself, which, as I already said, I want to place at the end of my square. I decided to make the thickness of the square 20 mm. Considering that the side plates are 2 mm thick, the end plate should be 16 mm wide.
To make it, I needed thin metal with good magnetic properties. I found it in the case of a faulty computer power supply:
Having straightened it, I cut out a strip 16 millimeters wide:
This is where the magnets will be placed. But here one problem arose: the magnets, having a curved shape, do not fit into the width of my plate....
(A little about the magnets themselves. Unlike acoustic speakers, hard drives use not ferrite, but so-called neodymium magnets. They have a significantly higher magnetic force. But, at the same time, they are more fragile - even though they are They look like solid metal, they are made of sintered rare earth metal powder. And they break very easily. In a hard drive, they are glued to a steel chassis, which, in turn, is already screwed on.)
I did not peel off the magnets from the steel plates - I only need one working plane from them. I simply cut off the protruding plates with a grinder, and a little of the magnets themselves.
In this case, a regular abrasive wheel (for steel) is used. Rare earth metals have the property of spontaneously igniting in air in a highly crushed state. Therefore, do not be alarmed - the “fireworks” of sparks will be much stronger than expected.
I remind you!!!
Permanent magnets are afraid of strong heat!! And especially - sudden heating! Therefore, when cutting, they MUST be cooled!
I simply placed a container of water next to it, and periodically lowered the magnet into the water after making a small cut.
So, the magnets are cut off. Now they fit on the strip.
Inserting long M5 screws into the holes for the rivets and securing them with nuts, I bent the following complex structure around the perimeter of the template plate:
It is on this that the magnets will be located inside.