Users are often wary of magnets lying near electronics. Someone told us, or we saw it ourselves: these things can easily distort the image, or even permanently break expensive gadgets. But is the threat really that great?
In contact with
Imagine the situation: magnets were bought as a gift for a child. Less than an hour later, these things end up near the computer, near the smartphone, near the TV... Dad’s many months of salary are at risk. The father of the family selects the “magnets” and throws them on the far shelf, but then thinks: maybe it’s not so scary?
This is exactly what happened to DigitalTrends journalist Simon Hill. To find the truth, he decided to turn to experts.
Matt Newby, first4magnets:
“People have such ideas from old electronic devices - for example, CRT monitors and televisions, which were sensitive to magnetic fields. If you placed a strong magnet near one of these devices, you could distort the image. Fortunately, modern TVs and monitors are not so sensitive.”
What about smartphones?
“The vast majority of magnets you encounter every day, even some very strong ones, will not have a negative effect on your smartphone. In fact, there are also several very small magnets inside it that are responsible for important functions. For example, wireless magnetic induction charging is used.”
But it’s too early to relax. Matt warns that magnetic fields can still cause interference with some sensors, such as the digital compass and magnetometer. And if you bring a strong magnet to your smartphone, the steel components will be magnetized. They will become weak magnets and will not allow the compass to be calibrated correctly.
Don't use a compass and think it doesn't concern you? The problem is that other, sometimes very necessary, applications need it. For example, Google Maps requires a compass to determine the orientation of a smartphone in space. It is also necessary in dynamic games. For owners of the latest iPhone models, magnets may even prevent them from taking photographs, since the smartphone uses optical image stabilization. Therefore, Apple does not recommend that manufacturers of official cases include magnets or metal components in their products.
Next up are hard drives
The idea that magnets easily destroy the contents of HDDs is still very popular today. Suffice it to recall an episode from the cult TV series Breaking Bad, where the main character Walter White uses a huge electromagnet to destroy digital incriminating evidence on himself. Matt takes the floor again:
“Magnetically recorded data can be damaged by magnets—this includes things like tapes, floppy disks, VHS tapes, and plastic cards.”
And yet, is it possible that what Bryan Cranston’s character did could happen in real life?
“Theoretically, damage to a hard drive by an incredibly strong magnet if you bring it directly to the surface of the drive is possible. But hard drives contain neodymium magnets...a regular sized magnet won't hurt them. If you, for example, attach magnets to the outside of your PC's system unit, this will not have any effect on the hard drive."
And if your laptop or PC runs on a solid-state drive, there is nothing to worry about at all:
“Flash drives and SSDs are unaffected by even strong static magnetic fields.”
At home we are surrounded by magnets, says the expert. They are used in every computer, speaker, TV, motor, smartphone. Modern life without them would simply be impossible.
Perhaps the main danger posed by strong neodymium magnets is the danger of being swallowed by a small child. If you swallow several at once, they will be attracted to each other through the intestinal walls, Matt warns. Accordingly, the child cannot avoid peritonitis (inflammation of the abdominal cavity - editor's note), and, therefore, immediate surgical intervention.
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, there is a general trend towards a decrease in quality: modern hard drives fail quite often. Old ones, with one or two gigabytes (or even much less), are all working!!! But they can no longer be used - they have very little 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:
Since the plate itself will be fixed only in places where the rivets pass through it, it will “spring” a little. That is, the magnets will attract it to the workpiece with its entire plane.
The next step is painting. There was no need to paint it. The stainless steel was decoratively polished, and the appearance was at a sufficient level.
But the fact is that in this case, painting is needed not so much for decorative purposes, but for practical ones: when working with metal, the square should not get lost among the many metal structures! Moreover, it can easily be accidentally carried away, stuck to the metal! That is why it should be bright in color.
Hello dear friends. Today we will disassemble the hard drive into small pieces in order to obtain neodymium magnets and other useful little things. Of course, we will disassemble the hard drive that has become unusable. So let's get started. Let's prepare all the necessary tools. In this case the following will be used:
1. Paper, A4 format - 3 sheets;
2. A set of thin Chinese screwdrivers;
3. Another Chinese set - a screwdriver with different attachments;
4. Box for small items;
5. Possibly a kitchen knife, although it is not in the photo;
6. And, of course, the hard drive itself.
Safety precautions:On the one hand, it seems nothing dangerous, but still be extremely careful. You will have to work with a knife, thin screwdrivers and other tools. If used improperly, you can easily get injured.
After that, take a screwdriver and a suitable attachment in your hands. In my case, this is a curly six-pointed nozzle. For some reason the cunning Chinese decided to use such bolts in the manufacture of this hard drive.
Having unscrewed all the bolts, tear off the stickers from the top cover. As a rule, several more bolts are hidden under the stickers. We also unscrew them, after which we carefully remove the cover and set it aside. We don’t throw it away either, it’s perfectly polished and we’ll need it someday. After opening we see the following picture.
Next, more subtle work begins. Turn the hard drive over to the other side and begin to unscrew the board. This operation must be done with extreme caution so as not to damage the board parts and other fragile elements.
Having unscrewed the board, turn the hard drive over again and pay attention to this element. This is our ultimate goal.
It is here that the neodymium magnet is hidden, for the sake of which all this was started. In general, we unscrew everything that can be unscrewed and remove the head.
I don’t know why we might need it in the future, but we will start using plates with neodymium magnets today. Please note that initially it may seem that the plates are twisted, glued or otherwise secured to the other. However, it is not. In fact, they are simply very strongly attracted to each other due to the force of magnets. Pay attention to the following photo - these are neodymium magnets.
Separating the magnet itself from the metal plate can be very difficult at times. In some cases, the magnets are glued, and in others they are held in place only by their own strength and thanks to the guides so that they do not move from the desired place. In my case, they stay in the right places thanks to the guides.
To separate the magnets from the metal plate, I pry the magnet from below with a knife blade. I just ask you to be careful! It's very easy to cut your hand. In the photo above you can see the already separated magnet. There are two of them in the hard drive. Although, to be precise, there are three of them, but the third one is very small. In some cases, the third magnet is a small cube with edges up to 1 mm. In some, the small ball is less than 1 mm. I would also like to draw your attention to the fact that some hard drives do not have two plates with magnets, but one curved in the shape of a horseshoe. In the next photo you can see an example of such a plate.
In this case, you have to use heavy artillery, such as pliers, to separate the magnet. In this photo, the plate was bent, and a knife blade was inserted into the resulting space between the plate and the magnet. I also want to warn you that different hard drives have magnets of different sizes. The largest ones, of course, are in older models. Here are examples of magnets from different hard drives.
Or at retail, but few people know that in some cases there is no need to buy it, since it won’t be difficult to get such a thing.
To obtain the desired result, you need to take a regular hard drive, which is equipped with any computer, but it must be non-working or outdated, since it will need to be disassembled.
Preparing to extract an element
In addition to the hard drive itself, for extraction you will also need a piece of ordinary A4 or A3 paper, a set of thin screwdrivers, an ordinary kitchen knife, and also some kind of box where you can put various detachable parts.
Removal procedure
The first step is to remove the cover of the device. To do this, you need to remove the jumper and unscrew several bolts, then peel off the stickers, under which, as a rule, several more bolts are hidden, which also need to be unscrewed. Next, the cover, which is not fixed by anything, can be removed without any problems, and the next item is the board, under which there is a head with neodymium elements. In order to remove the board, you need to turn the hard drive over and unscrew the bolts securing the board. Next, access to the target is open - metal plates with neodymium magnets are removed from the head, which will not be so easy to separate.
At first glance, it may even seem that they are glued or screwed to the plates, but this is not the case, and therefore, to overcome the force of attraction, it will be enough to use an ordinary kitchen knife, with which you can separate the plates from the magnets. When performing this, at first glance, simplest task, you cannot neglect the tenets of safety precautions, since you can cut your hand in an instant.
Advantages and disadvantages of neodymium elements from hard drive
The only drawback is the fact that the obtained elements cannot be used in all areas. For example, they certainly won’t be able to act as an elegant souvenir, but they perform all other functions.
There are many advantages to neodymium magnets extracted from a computer hard drive, and the main one is cost, since most often it is completely free, since an old, useless hard drive has no value. You can rummage around in search of such a part or offer to get rid of it to your friends and acquaintances.
Use of neodymium magnetic products from hard drive
As mentioned earlier, mined magnetic products are unlikely to be suitable for gifts or souvenirs, but they retain all the properties characteristic of the neodymium-iron-boron alloy. Ultra-strength and resistance to demagnetization contribute to their wide range of applications. You can use them to search for metal objects, or you can save your family budget by stopping the counter using such a product. Mined elements are perfect for this, as they have sufficient power. In addition, the “catch” can be attached to the fuel line, which will reduce fuel consumption and, again, save money.
Thus, an old part can serve well and provide a very valuable part that can be useful in everyday life and save the family budget. The main thing is not to rush to throw away unnecessary things, but to think about whether they will be useful in the future?
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 relationship between Russian and English terminologies describing the components of hard drives.
For clarity, let's look at a 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). It performs the functions of electronic control of the 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) for controlling other components located on the printed circuit board and transmitting data via the SATA interface.
- Read/write channel - a device that converts the analog signal coming from the heads into digital data during a read operation and encodes digital data into an analog signal during writing. 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 printed circuit board has 32 MB of Samsung DDR memory installed, which in theory gives the disk a cache of 32 MB (and this is exactly the amount given in the technical specifications of the hard drive), but this is not entirely true. The fact is that the 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 drives (from about 2004 and newer, but the exception is Samsung hard drives and those with Seagate stickers), flash memory contains tables with mechanics and head settings codes that 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. When there is a power surge, the TVS burns out, creating a short circuit to 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 requires very clean air to function properly. 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 of 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 by 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 that the hard drive is currently 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 sharp change in position due to the large value of the 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 disk contributes to leakage, so it is important to monitor the operating temperature.
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.