Bulgarian Makita 125 mm do-it-yourself repair

In detail: grinder Makita 125 mm do-it-yourself repair from a real master for the site my.housecope.com.

Many are familiar with the situation when a favorite tool stops working for no apparent reason. And if the grinder does not turn on, then, often, the reason for this is a simple breakdown, which can be quickly eliminated without special knowledge and tools. Next, we will consider simple methods for diagnosing and repairing power tools using an angle grinder as an example. Initial state - the angle grinder does not start when the power button is pressed.

To perform the work, we need a multimeter with a ringing function and a screwdriver. The first thing to check is the wire, or rather, the plug and the place where the wire enters the case. We press the button and “massage” suspicious areas. Most often, problems arise in the body. If this does not help and the grinder still does not work, go to the next step.

We disassemble the body. To be sure, you can turn on our tester in ringing mode and check the integrity of the wires from the plug to the button input.

Next in the electrical circuit is a button. Often, it is the malfunction of this node that is the reason that the grinder does not start. In order to check this node, you need to turn it to the ON position, and “ring”, as shown in the following photo:

In this case, the button "rang", which indicates its serviceability, so let's move on. This angle grinder uses a speed controller, so it is also worth “ringing” it, having previously set it to maximum power.

The next thing to pay attention to if the grinder does not turn on is the brushes. In large angle grinders, the brush holders are located outside, in our case - inside the housing. Remove the brushes and inspect them. It is necessary to make sure that the contacts on the brush itself are intact. The main criterion for the performance of a brush is its degree of wear or size. In this angle grinder, it was their wear and tear that caused its failure. Therefore, replacing the grinder brushes will help fix the problem. For clarity, a comparison of new brushes and completely worn ones is given.

Image - Bulgarian Makita 125 mm do-it-yourself repair

If in your case all this turned out to be working, and the grinder does not work, then the last thing you can check without a special tool is the anchor. To begin with, we “ring” between the iron parts of the anchor and the collector lamellas. If it rings, it means that there is an insulation breakdown and the anchor must be replaced.

Next, you need to measure the resistance between adjacent lamellas on the collector. It should be the same for all pairs. If, at any point of measurement, the resistance is several times higher, then we can talk about a winding break. It is worth noting that such a malfunction rarely leads to a complete engine stop.

If, after carrying out the above diagnostics, it was not possible to identify the malfunction and the angle grinder does not turn on, then it seems that you will have to contact the master.

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Most of the tools used in the household are not insured against breakage. Bulgarians, which almost every master has, fail over time. Different models of angle grinders may have a similar type of malfunction. But each brand has its own characteristics in design and components. The well-known brand Makita is valued for its high quality - durability. However, devices of this brand also tend to break.

Repairs can be done at home. Spare parts for the machine can be easily purchased. Before repairing the device, you must familiarize yourself with the attached diagram.

Video (click to play).

Types of Makita brand angle grinders and their features

Based on the diameter of the working circle, the grinding devices of the brand are divided into classes:

Lightweight - have a circle with a diameter of 115-125 mm. They are easy to manage.
Medium - the diameter of the circle is 150–180 mm. There are professional models and household ones, distinguished by motor power.
Heavy - disc diameter 230 mm. This class is represented by models for professional purposes when working with concrete, brick, etc. Featured with the latest security systems.

Amateur devices vary in power and price. Professional equipment is designed for long-term heavy loads and has an increased power reserve. Models with power above 1000 W are equipped with a comfortable rear handle, which is covered with special pads that protect against vibration.

As for the design of the grinders of this brand, it is characterized by the presence of such additions:

labyrinth device, which serves to protect against dirt and dust;
armored coating of motor windings;
special system for soft start and overload protection (Super-Joint-System).

Malfunctions when working with Makita angle grinders can be divided into two types:

electrical (breakage of the rotor, stator or defects in the control circuit);
mechanical (breakage of the bearing on the gear of the gearbox).

First you need to inspect the device. The mechanism of the grinder is to supply torque from the rotor through a gear to the spindle of the working body (circle, cutting stone).

Sources of breakdown can be increased loads, untimely replacement of brushes, lubricants. Due to the presence of a quick-release protective cover, Makita models are repaired in a short period of time.

There are components in the control circuit that you can troubleshoot yourself. Brushes are the weak point. Therefore, their verification is necessary first of all. You should also check the integrity of the power circuits from the plug to the switch terminals.

If the fault is a broken switch, then you need to replace it. If the supply wire is damaged and broken, then the damaged parts are removed or the entire wire is replaced.

The appearance of an unpleasant odor, constant overheating and spontaneous acceleration indicate a breakdown of the stator. The stator winding may break or a short circuit may occur. Using a tester or IK-2 device, you can find a short circuit. In the event of a malfunction, wind a new wire.

The cause of the breakdown of the angle machine may be the failure of the stator. This can be understood by the large number of sparks in the collector area and the presence of a burning smell. The rotor is connected to the gearbox. Therefore, when removing, it is required to disconnect it from the gearbox. Rotor repair is a complex technology. It will be more practical to replace with a new part.

The new rotor is placed in the housing with the bearings already mounted. And the drive gear is also put on. Then you should check the pressing of the bearing and tighten the nut.

Then the rotor with the gearbox is placed in the stator. In this case, the bearing should be closed with anther and spin easily.

If the gearbox is damaged, the spindle shaft will play. The gearbox starts to wedge, and the gear is slipping. Repair of the gearbox is usually associated with damaged gear teeth. For each Makita model, the driven gears are either attached to the shaft or pressed onto the spindle. In addition to the driven gear, the gearbox consists of a housing and a drive gear. To repair the angle grinder, you need to replace the gears, and you should replace them in pairs. You will need a puller to remove the driven gear. You can also use a press. It is not recommended to use a hammer due to the fragility of the case shell.

After troubleshooting the grinder Makita, components are purchased and repairs are made. The following recommendations should be followed:

it is necessary to start the assembly by checking the parts for integrity and cleanliness;
assembly begins with putting the bearing on the spindle;
after the bearing, the driven gear is installed;
the spindle is placed in the gearbox housing, while a rubber ring is used;
bolts during assembly of the gearbox are lubricated with sealant;
when laying lubricant in the gearbox housing, the volume of its space is taken into account (the volume of lubricant is equal to 1/3 of the volume of space);
at the end of the assembly, the torsion of the gearbox is checked and the bolts for fastening are screwed;
carbon brushes are replaced after 7 thousand hours of operation or wear up to 8 mm in length.

Makita Bulgarians are very often subjected to a repair procedure due to the high number of counterfeit devices. A common problem is the breakdown of the gearbox, namely, its gears.

In addition to the popular Makita brand, other grinding devices of the brands Bosch, Sparky, Stern are known. All of them are reliable and easy to use. But failures are not ruled out.

Bosch Bulgarians often require bearing replacement. The mechanism of the machine is based on the torsion of the spindle shaft, which is pressed into the driven gear. And also it relies on a needle bearing. If the bearing is destroyed, then its holder is very difficult to get. Moreover, the drive gear is fixed to the rotor shaft with a left-hand thread. As a result, fixation with a nut occurs. The driven gear is pressed onto the spindle shaft.

The gearboxes of the grinders Sparky are characterized by a gear pair placed in the housing. The driven gear is fixed by a press or keyed connection. The key is a ball of small diameter. The drive gear is also fixed to the rotor shaft with a key or a right-hand threaded nut. Even grinders of this model are distinguished by easy extraction of brushes without removing the handle.

When disassembling the Stern grinders, the gearbox can be left out of the case. During the repair, watch the small gear key, which does not hold well. The lubricant must be changed in a timely manner.

You can and should try to repair any tool. Bulgarians do not differ much in terms of mechanism. The diagram is always included with the purchase of the device. Therefore, any craftsman who has the necessary tools and devices can carry out repairs of working units with his own hands.

The Bulgarian, being the most demanded tool in the house, is subjected to considerable loads and intensive use. Because of this, after some time, it happens that jerks, a burning smell and other malfunctions appear when starting the engine, suggesting that the angle grinder (angle grinder) has broken down. But do not immediately carry the device for repair or buy a new one. Most of the malfunctions of this device can be eliminated independently.

Over the long years of the existence of such a tool as an angle grinder, its appearance, as well as the internal structure, have not changed much. To repair the grinder with your own hands, you need to know the device of its mechanical part, as well as the electrical one.

If you look at the figure below, you can see what parts the angle grinder consists of.

Wheel for adjusting the spindle speed of the unit.
An electric motor consisting of a rotor and a stator.
Start button. Sometimes a soft start system is connected to it.
Housing made of impact-resistant plastic.
Button for locking the spindle (used when changing tools).
Safety clutch. Protects the motor from overload when the tool jams.
Protective cover. Closes the tool and protects the user from flying particles of the processed material, and also prevents injury to a person when the tool is destroyed, for example, an abrasive disc.
A nut holding a tool. It is unscrewed using a special key that comes with the power tool. There are also quick-lock nuts that can be unscrewed without a wrench.
The gearbox housing and the gearbox itself. It consists of a block of gears that transmit rotational movements from the rotor to the spindle with the tool.

The figure below shows electric circuit grinder.

The electrical part of the angle grinder has the following elements:

electrical cable with a plug for connecting to the mains;
start button;
stator;
electric brushes (carbon or graphite);
collector;
anchor (rotor).

The following figure shows grinder connection diagram, namely its engine.

All components of the electric motor perform certain functions.

Rotor - this is the shaft on which the coils and the collector are placed. The rotor, rotating in the magnetic field of the stator, transmits rotational motion to the angle grinder gearbox.
Collector. It is a part of the rotor to which all control cables are connected. Electrical signals from the control unit to the engine pass through the collector. It is to the collector that the electric brushes are connected.
Electric brushes. Their main task is to transfer electric current from the power cable to the collector.
Stator. It is a coil with a certain number of turns. The task of the stator is to create a magnetic field, which, interacting with the armature, sets the latter in motion.

According to statistics, most cases of angle grinder failure are associated with the electrical part of the apparatus. Some breakdowns can be minor, which allows you to repair the grinder with your own hands. But, for example, if the motor windings burn out, only a specialist can repair an angle grinder.

The reasons that the angle grinder does not turn on may be the following:

electrical plug is defective;
defective electrical cable;
start button broken
the contact between the power cable and the button is broken;
breakage of the contact wire of the electric brush;
strong wear of electric brushes;
failure of the rotor or stator windings.

The reasons why the angle grinder is not gaining momentum can be different.

Breakdown of the speed control unit. To check this version, it is necessary to connect the device's motor directly, bypassing the regulator, and check the operation of the device.
Electrical cable failure due to permanent kinks or mechanical damage. Because of this, the damaged wire begins to heat up under load, and the engine speed drops.
Collector pollution with dust. Alcohol stains must be removed.
Brush problems. They may be worn or have a short contact wire, as shown in the following photo.

The brush, although half worn out, is quite functional. In this case, a short contact wire does not allow the spring to press the electrode against the collector. This situation can also be the reason why the angle grinder stopped working in normal mode.

The reasons why the grinder is warming up may be as follows.

Incorrect operation of the machine. As a result of overloads, the electric motor can become very hot, which often leads to burnout of the windings.
Bearing destructionlocated at anchor. As a result, the rotor clings to the stator, the operation of the motor is difficult, and the windings overheat. The problem is solved by replacing the bearings.
Clogged ventilation ductsthrough which air enters to cool the engine. The ventilation openings must be cleaned of dust.

Impeller failureused to cool the engine. It is installed on the rotor, on the side opposite to the collector. If the impeller is broken, it must be replaced with a new one.

Interturn short circuits stator and rotor windings. You will need to rewind the coils or replace these parts with new ones.

If you notice a strong spark when you turn on the angle grinder in the place where the collector is located, then the causes of this trouble may be as follows.

To diagnose the electrical part of the angle grinder, as well as eliminate the mechanical breakdowns of the device, you will need to disassemble it. Disassembly is carried out according to the following algorithm.

Unscrew the handle.

Remove the protective cover.

Open the special windows located on the sides of the angle grinder casing and remove the electric brushes after disconnecting the terminals.

Unscrew the gearbox housing from the angle grinder motor housing.

Gently pull on the gearbox housing and detach it from the casing. In this case, the gear unit will be removed together with the rotor.

After removing the armature, the motor stator will remain in the casing, which is also easily removed for diagnostics after unscrewing the fasteners.

To disassemble the gearbox, unscrew the screws holding the cover. After removing the cover, you will see the gears of the gearbox.

To remove the anchor from the grinder, you will need to unscrew the nut inside the gearbox.

In order to remove the bearing from the armature, it is recommended to use a special puller. Otherwise, the shaft may be damaged.

As mentioned above, most often the angle grinder refuses to work due to breakdowns in the electrical part of the unit. For the correct diagnosis of the electrical circuits of the tool, electrical repairmen use a special device - tester.

If you pressed the start button of the unit, and it does not work, then in 90% of cases the cause of the breakdown is not so serious that you cannot repair the grinder with your own hands.

Experts advise adhering to the basic rule of repairing power tools: move from simple to complex.

First of all, you will need checking the electrical cable and plug at its end. If it is collapsible, then unwind it and check the reliability of the contacts. Otherwise, you will have to disassemble the grinder (remove the casing of the device) and “ring out” the cable with a tester, and also make sure that the current is coming to the contacts of the “Start” button. If the device shows a break, then the cable should be replaced with a new one.

The situation when the current flows to the button, but does not pass further (when the position is on), speaks of switch malfunction. The button can't be fixed. It must be replaced with a new one, but first mark the contacts to be removed in order to connect them correctly in the future. If the contacts are connected incorrectly, the motor winding may burn out.

If during the test it turned out that both the cable and the start button are working, but no current is supplied to the brushes, then it is necessary to cleaning the contact plates of the brush holders. If this procedure is ineffective, it is recommended to replace the brushes. Further, if everything is fine with the brushes, and current is supplied to them, you should check the rotor and stator for short circuits and breaks.

The rotor of the electric motor may have the following malfunctions: interturn short circuit and breakage of conductors at the contacts of the lamellas. You can check the anchor of the angle grinder with a multimeter: the device is switched to the resistance change mode, the value is set to 200 ohms, and the resistance between two adjacent lamellas is measured using probes. Thus, it is required to check all pairs of lamellas. If the resistance values are the same, then the rotor winding is not damaged. Detection during the “ringing” of other resistance values, as well as the detection of an open circuit, indicates a malfunction in this coil. In this case, repair of the anchor of the angle grinder will be required.

Typically, a conductor break occurs at the junction with the winding. Inspect the places where the coils are connected to the lamellas, make sure that the soldering of the contacts is reliable.

If you do not have a measuring device, then you can check the rotor by using 12V bulb and battery. Power should be in the range of 30-40 watts. The check is done as follows: apply 12 V voltage from the battery to the plug of the angle grinder, connect a light bulb to the gap of one wire, start rotating the angle grinder spindle. With a good winding, the light will burn evenly, without blinking. With an interturn circuit, the degree of incandescence of the bulb spiral will change.In this case, repairing the anchor of an angle grinder with your own hands will be difficult, since the anchor winding scheme is quite complicated, and the process itself requires special equipment and knowledge. Therefore, this operation is recommended to be entrusted to specialists. But the best way out of the situation would be to replace the anchor on the angle grinder with a new one.

If the lamp does not light up when testing the rotor, this indicates an open in the stator or a short circuit in its windings, as well as problems with the electric brushes.

To check the stator of the grinder, use, as in the previous case, a multimeter. Values needed set to 20-200 ohms and do the following. Touch one probe to the contact of the stator winding, and the second to the body of the part. If the device shows resistance, this means that a breakdown has occurred on the case. Touch the probes to the contacts of one winding, and then to the contacts of the other. If the resistance is the same, then the coils are working. If the device shows an open circuit on one winding, then the stator will need to be rewound or the part replaced with a new one.

It will be problematic to rewind the stator at home without special knowledge, skills and equipment. It is better to contact specialists who are professionally engaged in rewinding engines.

The mechanical breakdowns of angle grinders include the following.Mechanical failures include breakage of the shaft retainer. In order to replace the retainer, you will need to disassemble the gearbox and remove the large gear.

In our service center you can not only repair your Makita angle grinder, but also get a free consultation on its further use.

Have you noticed that a tool always breaks down the minute you need it the most? And what to do? There is no time to run to the repairmen, and, perhaps, not to run. Maybe try to fix it yourself? After all, the gods did not. Let's take a grinder for a sample.

Any, even a very complex mechanism, consists of large and small parts. Bulgarian is no exception. Its main components and details:

Frame;
stator;
Rotor;
Reducer;
Connecting wire;
Switch.

The nodes can be divided into electrical and mechanical. Electrical - stator, rotor, connecting wire. Mechanical - housing and gearbox. Of course, there is also a button, fork, brushes.

Vala;
windings;
Contact collector;
Brush holder and brushes;
ball bearings.

For repairs, a minimum amount of tools is required - a screwdriver and a screwdriver with a special crown, pliers, a multimeter, electrical tape, grease for gearboxes. If we have all this, then we can proceed with the repair with our own hands.

To simplify the task, troubleshooting and repair must be performed systematically. No need to rush to disassemble the tool. First, let's determine the type of malfunction. The main trouble is that the grinder does not turn on. What to check:

Serviceability of the network socket;

Serviceability of the connecting plug;

Integrity of the connecting wire.

If these elements are serviceable, then we inspect the contact brushes. The brushes are used to transfer the supply voltage to the contacts of the motor collector. Armature windings are soldered to these contacts. If one of the brushes does not contact or is completely broken off, then the electric current will not flow to the winding and the grinder will not want to work. Image - Bulgarian Makita 125 mm do-it-yourself repair

In order to inspect the condition of the brushes, you must:

Find two coaxial threaded plugs on the body;
Carefully unscrew them;
Remove brushes.

The brushes are spring loaded, so be careful not to lose the springs. The removed brushes must be the same size. There will be some wear on them, but there should be no chips or transverse cracks that could break contact.

If the brushes are in good condition, then you will have to inspect the motor armature. This node is only called an anchor, but in fact it has absolutely nothing to do with an anchor. This is the central shaft of the engine, on which the winding and the collector ring are located. Sometimes, due to heavy loads, a strong spark occurs between the brushes and the collector contacts. As a result, copper contacts are covered with a layer of oxides and the current does not pass to the winding.

What needs to be done to put the anchor in order? You need to take the usual white rubber band, which is used by draftsmen and lovers of drawing. Use a rubber band to rub the contacts. The film of oxides should be clear and shine with a copper sheen.

If this operation did not give results, then it is necessary to open the case of the angle grinder and inspect the condition of the internal wires, the phase-shifting capacitor and the winding. The winding must have an even color of the varnish that is applied to the winding wire. Darkening or blackening of the wire or its sections indicates a short circuit of the winding. It is difficult to fix this malfunction with your own hands, you will need to replace the anchor.

The task of the gearbox is to transfer the rotation of the motor shaft to the grinder disk. Moreover, since we have an angle grinder, we also have an angle gearbox. To view it you need:

Remove the disk if it was installed;

Remove the protective cover;

Unscrew the four screws on the gearbox housing.

After that, the gearbox should come out of the housing. There are few errors here:

Breakage or significant wear of gear teeth;
Shaft failure;
Lack of fixation of gears on the shafts.

Damaged gearbox components must be replaced. Replacing a gear is not difficult. Then the gearbox is lubricated with a good layer of grease and installed in place.

The stator is that part of the electric motor that is fixedly fixed in the housing. It is designed to create an electromagnetic field in which the armature rotates. Image - Bulgarian Makita 125 mm do-it-yourself repair

The main malfunction of the stator is a winding break or its severe overheating. Why is overheating dangerous? When the winding wires overheat, the protective insulating varnish that covers them also overheats. Violation of the varnish insulation leads to a short circuit of the winding turns.

Even the closure of one turn of the winding completely disables the angle grinder. The winding immediately begins to overheat and smoke. The shaft rotates slowly or stops rotating altogether.

To repair the stator, you will have to change the windings to new ones or rewind them. But rewinding the stator is not a procedure for beginners.

Any instrument should be treated with care. The design of a modern instrument, by its very appearance, requires careful treatment. The plastic case, although it has a margin of safety, is afraid of shock. Try to use special soft stands for any instrument. Image - Bulgarian Makita 125 mm do-it-yourself repair

The housing has ventilation holes through which the motor is cooled.During operation, especially when cutting strobes, a lot of building dust gets into the body. Therefore, after performing dusty work, it is necessary to blow the inside of the grinder with compressed air. The outer surface of the tool must be wiped with a rag and dirt removed.

After completing the work, you need to remove the disk. This will relieve stress on the disk installation site, and at the same time you can inspect it and assess the condition.

Do not use a disc with a diameter that exceeds the size established for this angle grinder. A large-diameter disk can be compared to a large lever that you use to destroy the mechanism of a tool or burn out its electrical windings. In addition, it is impossible to install a protective cover.

After work, the electric wire must also be wiped, dirt removed, and especially oily. The wire must be carefully wound onto a coil, or at least onto the body of the grinder.

Many power tool users have the bad habit of pulling the plug out of the socket by the connecting cord. Because of this habit, the wire breaks, the socket loosens. This applies more to people who are sloppy and lazy by nature.

Avoid the possibility of getting water inside the angle grinder. When working outdoors, have a plastic bag or piece of plastic handy to cover the tool at all times and protect it from rain or snow.

In order for the grinder to serve for a long time and reliably, it is necessary to periodically open the gearbox, clean it and apply new grease.

Attention to the tool always has a beneficial effect on its long-term performance and your safety. And this should not depend on the brand of grinder - this is Makita, Sparka or our domestic sample.Is your grinder broken? It is not at all necessary to purchase a new tool: experienced specialists of the service center will make prompt and high-quality repair of the Makita angle grinder.

It should be well known that the device most often breaks down due to the fact that closed turns are formed in the armature winding or in the rotor or the stator burns out. In this case, it is necessary to replace the defective parts with new ones. The electrical part of the tool is the most vulnerable part of it. The main reason for the failure of the "electricians" of these devices is a very high load, water ingress or large voltage drops.

The most common causes of malfunctions in the mechanical part of the device are improper care of the teeth of the gearbox, bearings, or the fall of the angle grinder from a height. Before repairing the tool, you need to thoroughly clean its trigger mechanism, as well as the body. If after this the device does not turn on, then it should be disassembled in order to carry out a thorough repair of the Makita grinder.

What should I do if my device suddenly stops working? Disconnect the tool and rotate the disc by hand. If the disk could not be turned, then the complete disassembly of the angle grinder cannot be avoided in order to inspect its mechanical part. When the disc is spinning lightly, the cause of the malfunction is the failure to supply power to the motor brushes. In this case, check the operation of the start button or cord. If the cable is faulty, then remove the cover from the angle grinder handle, then ring two wires with the tester. If a break is found, replace the cable with a new one. You should also inspect the armature collector for the condition of the brushes. If they are worn out, replace the brushes.

When starting the engine with the switch button already pressed or when the disc jams, it often happens breakage of the retaining ring or the stopper itself. In this case, you should disassemble the "head" of the tool, remove the remaining parts, see if it can be repaired. If possible, then it is necessary to replace the parts that have become unusable, and if repairs are not possible, then special keys should be used to change the equipment.

Experienced specialists of our workshop will carry out warranty and post-warranty repair of Makita angle grinders.Note that the price at which it will result depends on the category of its complexity, which, in turn, is determined by the power of the tool, the nature of the malfunction, and the cost of spare parts. We use only original spare parts from the main supplier. By the way, we can also repair the Makita puncher, and of any complexity.

Video (click to play).

If you have any questions about instrument repair, please call: +7(495) 530-70-07 ext:120.

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