Heating should be carried out slowly, until the entire volume is completely warmed up - usually in the thermostat this takes 30...40 minutes. The coils may not withstand this temperature, so they must be removed before heating. If the epoxy cools down during cutting, heating must be repeated

What is a magneto?

Magneto is a magnetoelectric machine that converts mechanical energy into electrical energy. Currently, it is sometimes used in ignition systems for internal combustion engines. In telephony it is usually called an inductor.

Not every generator is called a “magneto”. This name applies only to generators in internal combustion engines:

excited by a permanent magnet and
combined in one product with an ignition coil.

The magneto magnetic system can be common to the emf generator. and ignition coils.

Often the spark plug is the only load on the magneto.

Design and operation

Magneto is a specialized alternating current generator excited by a rotating permanent magnet (magnetic rotor or armature).

An automobile magneto has low and low windings. high voltage. The breaker contacts and a capacitor (~0.1 µF) are connected in parallel with the low voltage (LV) winding; the leads of the high voltage winding (HV) are connected one to the housing, the other to the spark plug. All windings are wound on a yoke (core) and look like one large coil on a U-shaped core; between the poles of the core there is a longitudinally magnetized rotating magnet (telephone and mine-explosive (KPM) inductors are designed differently, but the principle of operation is the same). A low voltage winding can act as part of the high voltage winding, that is, an autotransformer design is possible, this allows you to reduce the number of turns of the high voltage winding.

Peculiarities.

Repair.

Ignition unit MB-1.

L1 – generator coil, d=0.063mm, W=11000 turns, R=3000 ohm; L2 – control coil, d=0.1mm, W=1200 turns, R=80 ohm; T1 – high-voltage transformer, d1=0, 28mm, W1=75 turns, R1=0.5 ohm, d 2=0.063mm, W2=6900 turns, R2=2000 ohm;E – electronic unit;C1 – capacitor 0.47 uF 630V;R1 – resistor 390 ohm 0 ,25 W;V1–V5 – diodes, correspond to KD 209;V6 – thyristor corresponds to KU 202

Before starting repairs, it is necessary to determine according to which circuit the ignition unit is assembled. Option one. It is necessary to measure the resistance of the generator coil L1 and the secondary winding of transformer T1, the resistance of the control coil L2 and the primary winding of transformer T1, it is not necessary to measure, it is enough to check them for an open. Then check the serviceability of the thyristor control circuit by measuring the resistance. We connect one probe to the sealed terminal going to resistor R1, the second to ground. In one direction, the resistance should be equal to the sum of the resistances of the resistor and the direct junction of the diode V5, approximately 2 - 4 kohms. In the other ∞. If all the windings and the thyristor control circuit are in good condition, it is necessary to make a drilling with a diameter of 1.5-3 mm at the point of connection of the anode of the thyristor V6 with the capacitor C1 (point A), and having soldered the coils, check the diodes V1-V4 and the capacitor for serviceability C1. If one of the diodes is faulty, it can be soldered by surface mounting, having first destroyed the old faulty diode by drilling. It is better to use a drill for this purpose.
If capacitor C1 is faulty, it must be removed, a new one inserted and the lead soldered to the indicated point, then filled back with epoxy glue.
If the thyristor malfunctions, I recommend replacing the block circuit completely, first removing the old one, soldering it by surface mounting and filling it with epoxy glue.

Additionally, if the resistance of the thyristor control circuit is greater than normal, the circuit's contact with ground may be broken; to restore it, it is necessary to: remove the M3 bolt from the glue, unscrew it, clean the contact and tighten it again, but with a new one (point B), or simply solder the hanging conductor , connecting it to the magneto housing. If the saw operates at high speeds intermittently, it is necessary to replace transformer T1. If after several minutes of operation the spark completely disappears, this indicates a malfunction of thyristor V6, it is necessary to replace the circuit. Option two.If the windings of the coils are in good condition (the resistance of the generator coil with one terminal can be ≈ 1 kohm, this is normal) - check whether the capacitor terminal soldered to the terminal of transformer T1 has not broken off. If all elements of the circuit are in good working order, I recommend turning the generator coil over, aligning the output wires. If at least one element of the circuit malfunctions, it is better to replace the circuit completely by soldering it according to the circuit of option 1, winding a coil with two terminals. If there is no generator coil with two terminals, you can install it with one terminal, but with insulation. It is enough to drill out the tubular rivet with a Ø5.1 mm drill and insert PVC tubeØ 4mm and when assembling, place fiberglass washers and a mounting tab for the second output.

A new magneto costs about 500 rubles, but if you have at least some skills in working with a soldering iron, then it is much cheaper to make an “eternal” magneto on your own and for almost nothing - the price of the parts is 12 rubles.

We will prepare the tools for work: soldering iron, tweezers, scissors, drill, screwdriver, multimeter. Materials: PCB plate 5x5 cm, thickness 1.5-2 mm, piece of wire 20 cm, solder, rosin. Details: thyristor KU202, diodes KD105 (KD106) - 5 pcs., resistance 1.2 kOhm.

First of all, by unscrewing two screws, remove the magneto assembly.

We unsolder the wires from the coil terminals.	Using a tester, we check the serviceability of the coils by ringing them for open circuits and short circuits to the housing.
Using a heated soldering iron, remove the top layer of compound from the electronic board...	...and, unscrewing the screw, remove the board.

Rice. 1. Methods for checking magneto coils.
	The ohmmeter readings correspond to the good condition of the coils.

Cut from PCB new board, we prepare the parts for installation.	Using wire cutters we shorten the thyristor leads. We saw off its leg according to the thickness of the nut, leaving 6-7 millimeters...
...and insert it into the hole in the board.	Screw and tighten the nut on the reverse side.
We solder the remaining parts according to the schematic diagram.	We try the assembled board in place and, making sure that the leads and solder points do not touch the body, screw it in with a screw.

We connect the leads of the diodes to the housing.	Solder coil L1.
We solder one terminal of the capacitor to the body, the other to the terminal from the thyristor nut.	We connect the thyristor leads with a diode and a resistance...

...and solder it to coil L3.

	Rice. 4. Installation diagram.

When heated to 140...150 degrees (Celsius), the epoxy becomes soft and can be cut with a knife, albeit slowly. Heating should be carried out slowly, until the entire volume is completely warmed up - usually in the thermostat this takes 30...40 minutes. The coils may not withstand this temperature, so they must be removed before heating. If the epoxy cools down during cutting, heating must be repeated.
There are MB-1 filled with organosilicon - this is a rubber-like mass that crumbles relatively easily and is removed without any additional tricks.

Regarding what is burning. Here my statistics are somewhat different from what uv cited. Papan. The capacitor, although it operates in extreme current modes, nevertheless often turns out to be in good working order. Most often the diodes turned out to be faulty, then the coils, then the thyristor, then the capacitor.

When replacing elements good results obtained with 1N4007 diodes and KU709V/KU712V thyristors. In principle, a diode can be installed counter-parallel to the thyristor - this will slightly increase the energy and duration of the spark. To further increase the values ​​of these characteristics, you can replace the half-wave rectifier with a bridge rectifier; the above-mentioned diode is not needed.

It is advisable to set the thyristor response level to 600-700 rpm - this will provide a larger range of regulation of the ignition timing (as they say now: torque) when changing speed, at the cost of a slight deterioration in starting. In any case, after replacing the thyristor or elements in the circuit of its control electrode, the installation of the UZ will almost always be damaged, which, in the absence of a stand, will require additional settings on the engine.

Adviсe

How to adjust the carburetor on a chainsaw?

If you have a need to adjust the carburetor of a chainsaw, then our article will help you. So, the carburetor has 3 adjusting screws: screw L - low speed, screw H - high speed and screw T - idle.

Using screws H and L, the ratio of air and fuel and lubricant mixture is adjusted, which is determined when the throttle valve is opened. If you tighten the screws (clockwise), the mixture becomes leaner and the speed decreases. If you unscrew the screws (counterclockwise), the mixture becomes richer and the speed increases. Using screw T, the idle speed is adjusted. In a clockwise direction, the number of revolutions increases and vice versa.

The main adjustment of the chainsaw carburetor is made at the manufacturer's factory when testing the chainsaw. The carburetor is adjusted to a mixture richer than optimal. This adjustment should remain during the first hours of operation of the saw. Then fine adjustments are made.

When the chain rotates at idle speed, screw T is turned counterclockwise until the chain stops. Precise carburetor adjustment is carried out only in a warm state by highly qualified specialists using special equipment (revolution counter). First of all, adjust screw L, after H and finally screw T.

1) First, you need to find the highest idle speed, while slowly turning screw L. After finding such revolutions, screw L is turned counterclockwise by 1/4 turn. In the case when the chain rotates at idle, you need to turn the screw T counterclockwise until the chain stops.

2) Adjusting screw H affects power and speed. If you adjust the carburetor to a lean mixture, you will get excessive speed and eventually the saw will fail.

After warming up the engine at full speed for 10 seconds, you need to turn screw H 1/4 turn counterclockwise. Next, the engine should run for about 10 seconds. We check the maximum speed using a tachometer. If the maximum speed does not coincide with the passport speed, then you need to repeat the operation. In this case, the engine should sound like a four-stroke.

3) Next, fine adjustment of the idle speed is carried out using screw T. If such adjustment is needed, screw T is turned clockwise with the engine running until the saw chain begins to rotate. And then the screw is turned in the opposite direction until the chain stops rotating.

If the engine accelerates immediately and sounds like a four-stroke engine at full throttle, then the chainsaw carburetor has been adjusted correctly.

Generator from spare magneto

To equip the motor with an electric generator, the capacitors should be removed from the magneto and mounted, for example, on the crankcase flange between the muffler and the ignition coils. It is better to place the capacitors in a protective case and secure them in such a way as to eliminate the possibility of vibration of both the capacitors themselves and their terminals.

The vacated threaded holes in the base of the magneto, intended for attaching capacitors, must be plugged with studs or rods made of aluminum alloy. You need to install a generator coil from another magneto on the racks, having previously squandered the space between the racks so that the coil frame fits there.

Pressing the core against the posts with shoes, you need to mark the centers of the holes for its fastening. Threaded holes for fastening the core should be made through.

The coil leads can be secured with clamps under the core fastening screws and passed through the holes in the base of the magneto.

The generator produces maximum power at a current of 1.5-1.7 A and a voltage of 18 - 20 V, so for the headlight it is necessary to select a light bulb that corresponds to these parameters. Bulbs rated at 1 A or less must have a nominal voltage of 24 V.

Characteristics

How to check the ignition coil (magneto) of a chainsaw?

Very often we come across situations when tool users come with faulty coils. Often the coils actually turn out to be faulty, but often the magneto has nothing to do with tool failure. The steps to check the serviceability of the ignition coil are described below.

Before you start checking the ignition coil, you should check the serviceability of the entire circuit. Do the following:

Visually assess the absence of cracks and visible defects on the coil body

Contamination of conductive elements and components

Serviceability and insulation of high-voltage and low-voltage wires, wire contacts, reliability of their fastening, absence of rust at fastening points

The high-voltage wire near the spark plug cap is often damaged - check for serviceability. Any “snot” in this place reduces the quality of the electric arc of the spark plug

Check the serviceability of the spark plug

Check that the circuit breaker is working properly.

Method 1: resistance measurement. This method is applicable when the resistance parameters of the coil windings are well known.

Method 2: using a device that checks for the presence of a spark. It is mounted in the open circuit between the spark plugs and the high-voltage wire of the ignition coil. The device is expensive and is used mainly in serious service centers.

Method 3: a little barbaric. It is used at your own risk in hopeless situations.

Remove the cap from the candle and insert a nail into it. Be careful not to damage the inside of the cap - then put it back on the candle and use it. If the nail has a head, it may be difficult to remove it.

Place the nail 6-7mm from the cylinder.

- “start” the saw, that is, perform the usual actions when starting the saw. This will force the ignition system to work. Please note that the candle must be screwed into the spark plug hole.

Look at the presence and color of the spark. Ideally, the spark should be “strong” and bright blue. Everything else is a sign of a malfunction.

Important points:

The spark plug must not be unscrewed: lack of compression will lead to faster rotation of the flywheel, which will not correspond real modes work

If there are electronic components in the ignition system, then this method can damage them

Basically, chainsaws and lawn mowers do not require setting ignition angles. Only the gap between the flywheel and the coil is adjusted. It should be 0.2-0.4mm (approximately the thickness of flat plastic on a water bottle or the walls of an aluminum can folded in half. They can be cut out and sandwiched between the flywheel and the reel). In each case, it is better to clarify the size of the gap in the instructions.

The distance between the nail and the cylinder simulates the compression and dielectric properties of the fuel mixture. Distance 6-7mm is approximate and may vary by different models products. But the philosophy is the same: there must be a large gap, the spark must be “strong” and bright blue

Magnets cannot fall out of the flywheel until there is excessive physical impact on them.

The coil is fastened securely enough and the screws are unlikely to unscrew on their own. Exception: initially loosely tightened

With your own hands

Four years ago I purchased a used mini-tractor AMZHK-8. It is equipped with a four-stroke two-cylinder carburetor engine SK-12-20 with an ignition system from a contactless left-hand rotation magneto 13.3728 with two sockets for high-voltage wires. At the time of purchase, the magneto was inoperative, and all attempts to bring it back to life were unsuccessful. There was not enough finance to purchase a new magneto after purchasing a mini-tractor, and there was no time to look for a new one.

An old decommissioned M-149A double-spark contact magneto of left-hand rotation turned up. After thinking a little, I removed the transformer, the distribution rotor (runner) and the coal from the distributor cover from the housing. What remains is a movable and fixed plate with a breaker and a capacitor. Instead of a magneto rotor, I machined a roller to the dimensions shown in the figure. On one end of the roller I pressed the magneto drive coupling half, and on the other - a cam with one protrusion cut off. The magneto bearings were replaced with ball-radial bearings No. 201.

The cam is pressed onto the almost assembled body and secured with a screw from the end of the roller, taking into account the ignition timing. I took the ignition coil from a Dnepr motorcycle. The B-204 coil has two high-voltage terminals. I placed it in a suitable plastic box in the place of least heat from the engine.

The wiring was done according to the motorcycle battery ignition circuit. The ignition is adjusted by turning the magneto housing in the mounting socket and turning the movable breaker plate.

The system has been working flawlessly for three years. The only condition is the presence of a battery.

Prices / Order

500 rubles

Firms

If you are interested in high-quality repair of chainsaws in Moscow, the Tekhnosad-Service service center has created optimal conditions for eliminating all possible problems. We know that gas chain tools require more maintenance than other garden equipment. There are several reasons for this. Firstly: dirty working conditions. Secondly: the high loads that chainsaws experience. Third: irregular use after long-term storage. Correct Maintenance and timely repair of a chainsaw is a guarantee of a long service life of the equipment and maintaining its efficiency.

We provide a full range of services for the maintenance and repair of chainsaws:

Chain sharpening
A sharpened chain has a decisive influence on the quality of the chainsaw. A saw with a dull chain will burn rather than cut through the wood. The saw chain tends to become dull easily when in contact with stones, metal or soil. Professional saw sharpening is the best way out. Only a professional can sharpen all the teeth evenly so that the saw does not lose efficiency.

Chain tension
Saw chains may stretch during use. A loose chain may break during operation. To ensure safe operation of the chainsaw, you should regularly check the chain tension at a service center.

Lubrication
The design of modern saws provides automatic lubrication. If this is not the case in your case, you will need to add oil every time you refuel. Due to lack of oil, the saw set may fail. After starting the saw, it is necessary to check the operation of the lubrication system: if the system is working correctly, oil splashes should be visible on the surface of the saw.

Protective equipment
To ensure safe operation of the chainsaw, it is necessary to periodically check the proper operation of the chain brake. The chain should stop at idle speed; if this does not happen, the centrifugal clutch must be serviced.

Fuel
Oil and gasoline must be mixed in a certain proportion. If the proportion is violated, the chainsaw engine can quickly fail. If you expect to use up gasoline within a month, it is worth adding a stabilizing additive to it. For an idle engine, it is best to have no fuel in the tank, thereby preventing engine malfunctions the next time you start it.

Maintenance
Essential engine maintenance includes such procedures as regular cleaning and replacement of the air filter, cleaning and replacement of the spark arrester, cleaning of the engine cooling fins, and replacement of the spark plug. In some cases, carburetor adjustment may be necessary.

Most chainsaw maintenance procedures can be performed independently, but only by entrusting the maintenance and repair of saws and other gas-powered tools to professionals, you guarantee safe operation and reliable operation of the gas-powered tool. Specialized service center Tekhnosad-service has all the resources to top level perform regular maintenance of chainsaws and power tools. http://www.service.tehnosad.ru/

Repair of the ignition unit of the Ural (Friendship) chainsaw

Ignition unit MB-1.

L1 – generator coil, d=0.063mm, W=11000 turns, R=3000 ohm; L2 – control coil, d=0.1mm, W=1200 turns, R=80 ohm; T1 – high-voltage transformer, d1=0, 28mm, W1=75 turns, R1=0.5 ohm, d 2=0.063mm, W2=6900 turns, R2=2000 ohm;E – electronic unit;C1 – capacitor 0.47 uF 630V;R1 – resistor 390 ohm 0 ,25 W;V1–V5 – diodes, correspond to KD 209;V6 – thyristor corresponds to KU 202

Before starting repairs, it is necessary to determine according to which circuit the ignition unit is assembled.
Option one. It is necessary to measure the resistance of the generator coil L1 and the secondary winding of transformer T1, the resistance of the control coil L2 and the primary winding of transformer T1, it is not necessary to measure, it is enough to check them for an open. Then check the serviceability of the thyristor control circuit by measuring the resistance. We connect one probe to the sealed terminal going to resistor R1, the second to ground. In one direction, the resistance should be equal to the sum of the resistances of the resistor and the direct junction of the diode V5, approximately 2 - 4 kohms. In the other ∞. If all the windings and the thyristor control circuit are in good condition, it is necessary to make a drilling with a diameter of 1.5-3 mm at the point of connection of the anode of the thyristor V6 with the capacitor C1 (point A), and having soldered the coils, check the diodes V1-V4 and the capacitor for serviceability C1. If one of the diodes is faulty, it can be soldered by surface mounting, having first destroyed the old faulty diode by drilling. It is better to use a drill for this purpose.
If capacitor C1 is faulty, it must be removed, a new one inserted and the lead soldered to the indicated point, then filled back with epoxy glue.
If the thyristor malfunctions, I recommend replacing the block circuit completely, first removing the old one, soldering it by surface mounting and filling it with epoxy glue.

Additionally, if the resistance of the thyristor control circuit is greater than normal, the circuit's contact with ground may be broken; to restore it, it is necessary to: remove the M3 bolt from the glue, unscrew it, clean the contact and tighten it again, but with a new one (point B), or simply solder the hanging conductor , connecting it to the magneto housing. If the saw operates at high speeds intermittently, it is necessary to replace transformer T1. If after several minutes of operation the spark completely disappears, this indicates a malfunction of thyristor V6, it is necessary to replace the circuit. Option two.If the windings of the coils are in good condition (the resistance of the generator coil with one terminal can be ≈ 1 kohm, this is normal) - check whether the capacitor terminal soldered to the terminal of transformer T1 has not broken off. If all elements of the circuit are in good working order, I recommend turning the generator coil over, aligning the output wires. If at least one element of the circuit malfunctions, it is better to replace the circuit completely by soldering it according to the circuit of option 1, winding a coil with two terminals. If there is no generator coil with two terminals, you can install it with one terminal, but with insulation. It is enough to drill out the tubular rivet with a drill Ø5.1 mm and insert a PVC tube Ø 4mm and during assembly add fiberglass washers and a mounting tab for the second output.

N. Tukmachev

Announcement! For sale is a semi-automatic machine for winding magneto generator coils MB-1. Inexpensive.

A device for checking the ignition unit of a chainsaw.

Currently, the market is saturated with chainsaws of foreign and domestic production, differing in appearance, size, power, but they all have one main detail in common - gasoline engines.

The ignition of the fuel-air mixture in the engine combustion chamber in previous domestic chainsaw engines was carried out by a spark obtained from a magneto, which was subsequently replaced by manufacturers with chainsaw electronic ignition unit(MB-1 and MB-2).

Situations arise when a chainsaw fails to operate precisely because the electronic ignition unit is not working.
How can you be sure of this? How to find the cause and eliminate it?

You can disassemble the ignition unit in parts and tinker with them, comparing them with working ones, or you can assemble a simple device that will help you determine a malfunction in the electronic ignition unit of a chainsaw in a couple of minutes.

How to make a device for checking the ignition unit of a chainsaw.

We have assembled a device that can accurately determine whether a chainsaw ignition unit is working or not.
The device consists of a horseshoe-shaped core assembled from a package of strips transformer steel, with a pulse coil and an excitation coil located on it.

The excitation coil (named according to our definitions) is designed to excite an alternating magnetic field, into which the electronic chainsaw ignition unit being tested is placed.

The impulse coil (also named according to our definitions) supplies voltage to the electronic switching system (signal coil), that is, the electronic commutator.

Technique for detecting a chainsaw ignition malfunction with a device.

The principle is this: near the ends of the horseshoe-shaped core, the chainsaw ignition unit under test is placed, and the high-voltage discharge is checked at the output of the high-voltage coil.

For the MB-1 and MB-2 units being tested, the output from the pulse (signal) coil is unsoldered (in some cases this may not be done if its resistance corresponds to the reference one).

• The block is placed near the ends of the device in such a way that the core of the charging coil is located in the gap between the ends of the horseshoe-shaped core.
• One end of the wire from the device’s impulse coil is connected to the metal body of the ignition unit, the other end to a tap located at the signal coil electronic unit.
• An external conductor (high voltage wire) with a spark plug installed on it is connected to the output of the high-voltage ignition coil.
• The spark plug body is connected to the body of the electronic unit being tested. Instead of a spark plug, you can use a high-voltage spark gap with an adjustable gap or a regular gap with high voltage wire on the housing of the electronic ignition unit.
• The device is connected to an alternating current network.
• If the electronic switching unit is working properly, then a discharge will be observed at the site of the high-voltage gap (arrestor) or the spark plug, with a working high-voltage coil.

The coils themselves are checked with an ohmmeter (tester) and under voltage.

An ohmmeter is used to check the compliance of the ohmic resistance of the coil windings with those specified by the manufacturer.

• Charging coil ≈ 3.26kΩ.
• High voltage coil:

1. From the coil body to the high-voltage terminal ≈ 1.4k Ω.

2. From the coil body to the capacitor terminal ≈ 1Ω.

• Signal (control switching) coil ≈ 69Ω.

If there is a clear resistance mismatch (usually reduced), you should think about burning through the insulation of the winding wire and shorting it internally.

The absence of resistance indicates a winding break.

The voltage storage capacitor is checked with a tester or replaced with a known good one.

You can check each coil of the ignition unit separately, without removing it from the unit itself or separately removed.
The core of the coil being tested should be located in the gap between the ends of the device core.

• The charging coil of the ignition unit in the magnetic field of the device produces AC voltage about 80v - 100v.
• The signal coil of the ignition unit (controls the electronic ignition switching) produces 5.5v-6.7(6.2)v.

The situation is different with a high-voltage coil, because it has three connecting points in the circuit: a high-voltage output, an output to the housing and an input from the capacitor.

• Between the high-voltage terminal and the terminal to the housing, the voltage will be about 50v-60v.
• Between the output to the case and the output to the capacitor - 0.4v-0.8v.
• Between the high-voltage output and the output to the capacitor - 47v-52v.

A monolithic electronic ignition unit can also be checked with our device, but such a unit cannot be repaired due to the type of design. You can only determine whether the unit is working or not.

Well, if a spark discharge was not observed when checking the electronic ignition, then the probable reason for this will be a malfunction of the electronic ignition switching circuit; its repair is simple for those who are at least a little familiar with a soldering iron.

Currently, the market is saturated with chainsaws of foreign and domestic production, differing in appearance, size, power, but they all have one main detail in common - gasoline engines.

The ignition of the fuel-air mixture in the engine combustion chamber in previous domestic chainsaw engines was carried out by a spark obtained from a magneto, which was subsequently replaced by manufacturers with an electronic chainsaw ignition unit (MB-1 and MB-2).

Situations arise when a chainsaw fails to operate precisely because the electronic ignition unit is not working.
How can you be sure of this? How to find the cause and eliminate it?

You can disassemble the ignition unit in parts and tinker with them, comparing them with working ones, or you can assemble a simple device that will help you determine a malfunction in the electronic ignition unit of a chainsaw in a couple of minutes.

How to make a device for checking the ignition unit of a chainsaw.

We have assembled a device that can accurately determine whether a chainsaw ignition unit is working or not.
Checking the electronic ignition of a chainsaw The device consists of a horseshoe-shaped core assembled from a package of transformer steel strips, with a pulse coil and an excitation coil located on it.

The excitation coil (named according to our definitions) is designed to excite an alternating magnetic field into which the electronic ignition unit of the chainsaw being tested is placed.

The impulse coil (also named according to our definitions) supplies voltage to the electronic switching system (signal coil), that is, the electronic commutator.

Testing the electronic ignition of a chainsaw. Technique for determining if the device is faulty in the ignition of a chainsaw.

The coils themselves are checked with an ohmmeter (tester) and under voltage.

An ohmmeter is used to check the compliance of the ohmic resistance of the coil windings with those specified by the manufacturer.

Charging coil ≈ 3.26kΩ.
High voltage coil:
1. From the coil body to the high-voltage terminal ≈ 1.4 kΩ.

2. From the coil body to the capacitor terminal ≈ 1Ω.

Signal (control switching) coil ≈ 69Ω.
If there is a clear resistance mismatch (usually reduced), you should think about burning through the insulation of the winding wire and shorting it internally.

The absence of resistance indicates a winding break.

The voltage storage capacitor is checked with a tester or replaced with a known good one.

You can check each coil of the ignition unit separately, without removing it from the unit itself or separately removed.
The core of the coil being tested should be located in the gap between the ends of the device core.

The charging coil of the ignition unit in the magnetic field of the device produces an alternating voltage of the order of 80v - 100v.
The signal coil of the ignition unit (controls the electronic ignition switching) produces 5.5v-6.7(6.2)v.
The situation is different with a high-voltage coil, because it has three connecting points in the circuit: a high-voltage output, an output to the housing and an input from the capacitor.

Between the high-voltage terminal and the terminal to the housing, the voltage will be about 50v-60v.
Between the output to the case and the output to the capacitor - 0.4v-0.8v.
Between the high-voltage output and the output to the capacitor - 47v-52v.
A monolithic electronic ignition unit can also be checked with our device, but such a unit cannot be repaired due to the type of design. You can only determine whether the unit is working or not.

Well, if a spark discharge was not observed when checking the electronic ignition, then the probable reason for this will be a malfunction of the electronic ignition switching circuit.

To assemble our electronic ignition circuit we used the following elements:

VD-KU201 (instead of BT136);
D1-EM516;
R1-27ohm(KF4-3);
C1-0.25-0.5uF(630v).
D2-IN4007(LD). When using the KU-201 thyristor, element D2 is not needed.

Circuit-ignition-chainsawThe entire assembly is located in the box of the block body instead of the old one.

The thyristor is shortened in the threaded part (anode). The cathode contact is also slightly shortened.

The entire assembly, after setting up and testing the unit on the device, is filled with silicone to protect it from moisture, dust and vibration.

The proposed circuit can be assembled by any beginner or person interested in electrical engineering. It contains a minimum of elements and is easy to assemble.

With your own hands

Repair

In the arsenal necessary tools Many summer residents have a chainsaw. This is an indispensable assistant when cutting down and trimming trees, when preparing firewood for the winter, during construction and in general. useful tool good owner. Unfortunately, the chainsaw sometimes breaks down and has to be repaired.

Of course, if you have a new chainsaw and it is still under warranty, then there is only one solution - take the saw to a service center, where they will carry out warranty repairs. When the warranty period has expired, repairs at the service will already be paid for. In this case, if you have at least some skill in working with equipment, it makes sense to try DIY chainsaw repair. In addition, the chainsaw is not such a complex mechanism as it seems at first glance, and the cause of the malfunction is quite simple.

So, what to do if the chainsaw won’t start? The first thing, of course, is to check the presence of fuel - gasoline in the filling tank. If there is fuel, we find the spark plug on the saw engine, unscrew it and see what condition it is in - is there any carbon deposits, is the spark plug filled with fuel. If the spark plug was filled with gasoline, then wipe it dry and additionally dry the combustion chamber of the cylinder. To do this, turn off the fuel supply and operate the starter several times. After that, screw in the spark plug and try to start. When inspecting the spark plug, you should pay attention to the gap between the electrodes - (0.5 - 0.65) mm. Then we check for the presence of a spark. To do this, we put a high-voltage wire on the spark plug, use pliers with insulated handles to press the spark plug body to the cylinder and pull the starter. If there is a spark, everything is fine; if not, the ignition system is faulty. Both the high-voltage wire itself and the ignition module may be faulty. Defective parts must be replaced.

Another very common cause of chainsaw malfunction is the fuel system. It is enough to disconnect the fuel supply hose from the carburetor - if gasoline flows, then everything is fine. If there is no gasoline or it only drips, then the likely reason is a clogged filter or breather. The filter is replaced with a new one, the breather is cleaned with a needle. Don't forget to change the fuel filter every 3 months of using the saw. The carburetor may also be out of adjustment or clogged. It must be adjusted strictly according to the instructions after washing and cleaning.

The air filter is checked; as a rule, it is very dirty. The filter is washed in water with detergent, then dried and put in place.

The chainsaw muffler is cleaned of dirt and combustion products, as this may be the reason why the saw stalls under load. More serious problems with the engine itself, with the pistons, require more serious repairs. Clean your chainsaw regularly, change filters, do not overload, and it will serve you for a long time and without problems.

Features of the chainsaw ignition

Checking the functionality of the electronic ignition of a chainsaw. Technique for determining if the device is faulty in the ignition of a chainsaw.

The principle is this: near the ends of the horseshoe-shaped core, the chainsaw ignition unit under test is placed, and the high-voltage discharge is checked at the output of the high-voltage coil.

For the MB-1 and MB-2 units being tested, the output from the pulse (signal) coil is unsoldered (in some cases this may not be done if its resistance corresponds to the reference one).

The block is placed near the ends of the device in such a way that the core of the charging coil is located in the gap between the ends of the horseshoe-shaped core.
One end of the wire from the pulse coil of the device is connected to the metal body of the ignition unit, the other end to a tap located at the signal coil of the electronic unit.
An external conductor (high voltage wire) with a spark plug installed on it is connected to the output of the high-voltage ignition coil.
The spark plug body is connected to the body of the electronic unit being tested. Instead of a spark plug, you can use a high-voltage spark gap with an adjustable gap or a regular break from the high-voltage wire to the body of the electronic ignition unit.
The device is connected to an alternating current network.
If the electronic switching unit is working properly, then a discharge will be observed at the site of the high-voltage gap (arrestor) or the spark plug, with a working high-voltage coil.

How to regulate a chainsaw

When purchasing a chainsaw, the store salesperson will definitely check the tool in front of you. However, this does not mean that she is ready to work. Before the first start, you will have to make certain settings and check the main components of the saw. Therefore, it is extremely important to know how to adjust your chainsaw so that it serves you trouble-free for many years.

To make the adjustment correctly, you need to become familiar with the basic elements and structure of the saw. For this, the operating instructions supplied with the tool are sufficient. Adjusting the chainsaw consists of the following steps:
- chain tension adjustment;
- carburetor adjustment;
- idle speed adjustment;
- ignition adjustment.

To adjust the chain tension, loosen the clutch cover nuts and turn the adjusting screw until the chain is in the desired state, that is, it should not be too loose, but it should not be too tight.

The chainsaw carburetor is adjusted at the factory. Therefore, it is not recommended to change anything in its settings. If you are not satisfied with its performance, then it is better to immediately contact a service center while the chainsaw is still under warranty. The same goes for ignition.

The idle speed at first start needs not so much adjustment as checking. To do this, you need to turn the idle speed adjustment screw clockwise until it stops, and then counterclockwise 4.5 turns. If after this the engine runs without rotating the chain, then everything is in order. Otherwise, we go to the service center. Working with such a saw is dangerous!

The settings may vary slightly in different chainsaw models. However, the basic principles of setting up a saw remain the same for all manufacturers of this tool.

Characteristics

Electronic ignition unit for chainsaw

Despite the widespread use of imported chainsaws, the population, especially in rural areas, still uses many domestic “Druzhba” and “Ural” machines. Both saws have general disadvantage, which I also had to deal with, is the fragility of the electronic ignition unit. This problem is not new - see the article by P. Ivanov “Repairing the ignition unit of a chainsaw” in Radio, 2003, No. 2, p. 45. Nowadays it is not difficult to buy a block, but it is expensive and does not last long. I decided to start developing my own design, which I bring to your attention.

Unlike the one mentioned above, the ignition unit does not contain remote elements and fits entirely into the original dimensions of the factory unit. The board of the old unit must be removed.

The block diagram is shown in Fig. 1. Generator coil L1, ignition coil (high-voltage transformer) T1, capacitor C1, induction ignition pulse sensor L2 and a duralumin base were used from an old ignition unit. The remaining elements are newly introduced.

Rice. 1 Schematic diagram devices

When the flywheel rotates, the generator coil L1 generates an alternating current, which, after rectification by the diode bridge VD1-VD4, charges the capacitor C1. At certain position flywheel, a short pulse of positive polarity appears at the terminals of the sensor coil L2, which, passing through the diode VD5 and the current-limiting resistor R1, opens the thyristor VS1. Capacitor C1 is discharged through the open thyristor and primary winding ignition coil T1. Its secondary winding forms a high voltage pulse, which is then supplied to the spark plug.

The amplitude limiter of the opening pulse is assembled on transistor VT1, resistor R2 and zener diode VD6. As long as the voltage on the control electrode of the trinistor VS1 does not exceed the stabilization voltage of the zener diode VD6, the transistor VT1 is closed and does not affect the control electrode circuit. When the zener diode VD6 opens, current begins to flow through it and resistor R2. A voltage appears across resistor R2, which slightly opens transistor VT1, which shunts the control electrode circuit of thyristor VS1. As a result, the pulse amplitude is limited to about 4 V at the zener diode indicated in the diagram. This voltage is enough to reliably open the thyristor.

In order for the described design to fit into the dimensions of the factory ignition unit, it is necessary to modify the thyristor. To reduce its length, the threaded shank was shortened (1-2 threads were left), the cathode and control leads were also shortened to a length of 4...5 mm. Before shortening the lead, it must be compressed in two places near the body using side cutters with blunt cutting edges. Then, above these places, the lead is bitten off and the cut is soldered with solder.

The terminal can be compressed no closer than 2 mm from the SCR body, otherwise the insulator will crack. This compression is necessary to increase the contact area between the internal conductor coming from the crystal and the external terminal of the SCR.

The block is installed rigidly copper wire with a diameter of 0.4-0.45 mm in vinyl insulation. Diodes VD1 - VD4 are assembled closely into a block and their terminals are soldered in such a way that on one side of the block there are AC terminals, and on the other - DC. The transistor is secured with the screw that was used to secure the factory board. A petal is placed under the transistor, to which the leads connected to the body are soldered. Resistors, diode VD5 and zener diode VD6 are soldered to the terminals of transistor VT1 by surface mounting.

Capacitor C1 is placed in the same place, and the bridge VD1-VD4 is placed in the same compartment. The wires from coil L1 to the bridge are flexible, of the same cross-section. The wire going to the anode of the thyristor is soldered to its body. Before filling with the compound, the thyristor is held “suspended” on rigid wires in such a way that it does not protrude beyond the dimensions of the unit, and a gap of about 2 mm remains between the thyristor body and the duralumin base of the generator. Assembled block After testing for functionality, fill it with epoxy compound, making sure that parts of all elements close to the edges and the SCR housing are covered with a layer of compound. After the compound hardens, the thyristor is rigidly fixed to the base of the generator. View finished block shown in Fig. 2.

Rice. 2 View of the finished block

When installing the unit in a chainsaw, it may be necessary to adjust the ignition timing. In practice, it was often necessary to set it earlier relative to the factory mark. If you plan to install the block in a Ural chainsaw, before assembly you need to remove part of the mounting protrusion from the back side of the base, painted in Fig. 3 in blue, flush with the base plane. Under the remaining parts of the protrusion, when installing the block in place, it is advisable to place gaskets made of heat-insulating material, such as asbestos cardboard, with a thickness of no more than 0.5 mm. With a greater thickness, the flywheel may interfere with the block parts. Gaskets are needed because the design of the Ural chainsaw provides for the installation of an electronic ignition unit directly on the wall of the engine crankcase, which becomes very hot during prolonged operation.

Rice. 3 Reverse side of the part

In the above block, instead of those indicated in the diagram, you can use diodes KD105G, KD209 with any letter index, as well as other suitable dimensions with a reverse voltage of at least 400 V and an average forward current of at least 0.3 A. We will replace the KS133A zener diode with KS 139, KS 147, KS 156 with letter indices A, B, G or their imported analogues, provided that the sum of the stabilization voltage of the zener diode VD6 and the voltage of the IBE transistor VT1 does not exceed the permissible voltage at the control terminal of the thyristor. SCR KU202N can be replaced with KU202M, KU205V, KU205G. Tri-nistors in a plastic case should not be used due to their insufficient resistance to overheating.

In conclusion, I will add that more than 20 blocks were assembled according to the description provided and they work for a long time and reliably. The unit I assembled and installed on my chainsaw 6 years ago has never failed

OPERATING PRINCIPLE OF A CHAINSAW

The main question that buyers ask themselves is the simplest: how to buy the right product? But even little-known brands have dozens of tools on sale, not to mention world-famous companies. How to choose the right one? To do this, it’s worth understanding what the main characteristics of a chainsaw mean, why they are highlighted, and whether large numbers always mean high performance, and not just the high cost.

Technical parameters are directly related to the design of the tool and the principle of its operation. For example, the power and permissible dimensions of the saw set depend on the size and type of engine. From the design and materials used - weight.

In general, the design of a chainsaw consists of a motor, torque transmission mechanisms and a saw blade. The engine and chain are connected by a gearbox (transmission system) and a clutch system. The saw blade is a bar with a chain placed on it. Since the chainsaw engine is two-stroke, it has 2 tanks - oil (for lubrication of the chain) and fuel (for the fuel mixture).

A fuel mixture is used rather than gasoline due to the structure of a two-stroke engine, which does not have a separate tank to lubricate its internal elements.

The tool works as follows: when the user pulls the starter “cord,” the crankshaft unwinds. If there is a sufficient amount of fuel mixture in the tank, then at one of the revolutions the spark plug fires - a spark ignites the mixture. When it burns, it releases gases that increase in volume, which push the piston. This element is connected through a connecting rod to the crankshaft, which by inertia goes to the second revolution, thereby continuing the process again without the participation of external forces. When the saw starts, the engine begins to spin the drive sprocket. The saw blade, in turn, is attached to it, and the chain, driven by the sprocket, begins to “walk” in the grooves of the bar. The chain is lubricated automatically when moving - after finishing work, turning off the chainsaw, you can notice that a certain amount of lubricating oil flows out of it. This is unspent oil remaining in the grooves.
Specifications
Engine volumes, fuel tank and oil containers

The size and capacity of the engine directly affect the power of the saw; the larger it is, the more energy is released to move the piston. The volume also indicates how much fuel the saw produces per certain time. It is worth considering that if the engine volume does not correspond to the power of the saw, this reduces its service life due to ineffective use.

The volume of the fuel mixture tank varies from 0.3 to 1 liter. Accordingly, the oil tank is 1.5-2 times smaller. This difference in volume helps, when the tool is fully loaded, to consume the fuel mixture and oil at almost the same speed (about 30-50 minutes).

For household-grade saws, the engine capacity reaches 40 cc, which is 1.5-2 hours without refueling. Semi-professional saws capable of working for 8 hours have an engine capacity of up to 60 cc, and professional ones up to 121 cc. Larger models are additionally equipped with starting aids.
Power

The larger the engine capacity, the more powerful the saw, and, therefore, the more productive. The speed and intensity of cutting depend on the power. This indicator is measured in “horsepower” or kW (1 hp = 0.735 kW). Depending on the power, saws are divided into classes and areas of application.
Up to 2 kW – household
From 0.74 to 2.94 kW – semi-professional
From 2.94 to 5.15-6 kW – professional

Chainsaws with high power require additional physical effort during operation and knowledge of safe use techniques, since operating such a tool is quite difficult. Equipment power may be reduced due to natural wear and tear on components, the use of a poor-quality fuel mixture, and incorrectly selected saw accessories.
Weight

Nominally, the weight of the saw is the sum of the weight of the engine and the body with handles. Knowing the weight, you can also get an idea of ​​the functionality of the equipment:
Household saws weigh on average from 2 to 5 kg. They do not need a lot of power and the main requirement for them is the convenience and ease of performing periodic small jobs (harvesting firewood, cutting branches).
Semi-professional saws weigh slightly more - 5-7 kg, which indicates higher power, and, accordingly, an expansion of the scope of work. Since this type of saw is often used as a lopper, the design includes lightweight tires.
As for professional saws, the weight of the most powerful of them can reach 11 kg. They are “lightened” by using lighter alloys (mainly magnesium-based) for the production of the cylinder and crankcase. The goal is to make the tool lighter, but not to reduce the service life, reliability and safety during operation of the product.

In fact, when using a chainsaw, the master experiences the load not only of these elements, but also of the weight of the saw set and fully filled fuel and oil tanks. Therefore, if small weight is an important criterion, you should give preference to household and one-handed saws - they are lighter than others. This parameter becomes decisive when choosing a tool for crowning - cutting the upper branches and throughout the entire crown of the tree. In this case, a heavy chainsaw is not only ineffective, but also dangerous - maneuverability is low, and weight and vibration powerful engine will quickly lead to fatigue of the master, it is difficult to hold it in weight and it is absolutely impossible to do it with one hand. Therefore for of this type work and recommend a specialized, lightweight tool.

It should also be taken into account that people who are contraindicated for intense physical activity are not recommended to use chainsaws that weigh more than 5 kg.

To work with a professional tool you need good physical training, because... For such saws, safety precautions do not provide for a belt fastening due to the high risk in the event of unforeseen complications during operation (a tree falling, for example). The operator must have time to release the tool, and not free himself from it.

The toothed stop makes it easier to operate professional saws. It is located on the body next to the saw bar, so when this element rests against a tree trunk, it is easier to hold the saw - it is no longer suspended.
Tire length

The tire is one of the main parts of the sawing machine. It is a support for the chain and a channel for its lubrication (due to the movement of the chain shanks in the grooves during operation).

An important characteristic of a tire is its length. It is this that determines the maximum thickness of the trunk that the tool can cut. The longer the bar, the greater the cutting depth.

As a rule, all manufacturers indicate the maximum length of the bar in the characteristics of the saw. If you install a tire larger than permissible on a compact saw, then due to lack of power, moving the chain along it will be an additional load for the engine. This will cause the entire saw set to wear out much faster and increase fuel consumption.
Chainsaws with short and standard (30-40 cm) tires are more often found in the household class, and for professional ones a length from 45 cm to 1 meter is possible. It is also worth considering that as the length of the tire increases, the recoil force against the resistance of the material increases.
Chain pitch

The saw chain is part of the sawing machine. Consists of links (teeth) fastened with rivets. Its parameters are chain pitch, profile height, drive link thickness and cutting depth. Among them, the main one is the chain pitch - this is the distance between three consecutively located rivets on the chain, divided by 2.

Chains are divided into five groups, depending on the step size:
14 inches (6.35 mm)

Miniature chains rarely used in Russia. They are installed on low-power one-handed saws.
0.325" (8.25 mm) and 38" (9.3 mm)

Low profile chains come with this pitch. More than 80% of saws produced worldwide are equipped with such chains. Also, they are the safest for inexperienced users due to the low probability of kickback and low vibration levels during operation.
0.404 in (10.26 mm) and 34 in (19.05 mm)

This step distinguishes a chain with increased productivity, having large links. These chains are used on harvesting equipment and heavy-duty felling saws. A large step, due to this, a larger layer removed in one pass, but, accordingly, the resistance of the processed material is also greater.
Additional properties
Availability of anti-vibration system

First of all, the use of such a system is necessary on professional models of chainsaws, because Long-term work with a powerful vibrating tool is quite detrimental to the joints and can lead to serious consequences.

Its simplest type is a set of rubber gaskets located between the handles and the body. However, such an anti-vibration system is practically not used in modern chainsaws. As a rule, the “two-mass” principle is implemented: the engine block is separated from the handle block and the fuel tank.

The dependence of the impacts of the chain elements on the material: a smaller step means a smaller layer removed in one pass, and accordingly, the resistance of the wood is also less. As a result, the vibration level naturally decreases.

In the absence of a normal anti-vibration system in the instrument, several years of use can lead to dire consequences, ranging from poor circulation in the hands to more serious diseases. However, some household chainsaws do not have an anti-vibration system. Its absence is explained, firstly, by the short duration of use of the tools, and secondly, by the fact that they do not develop high power and the chains on them have a smaller pitch.
Cutting speed

When purchasing a chainsaw, buyers often ask about the speed of sawing wood with a specific chain saw (for example, whether it is necessary to “press” on the entire tool when working). We answer: first of all, it depends on the condition of the saw set and, in particular, the chain. When working with a dull chain, not only will sawing efficiency be low, but the likelihood of saw failure increases as the load on the engine increases. Therefore, for professional use, it is recommended to regularly “true” the chain (for example, at the end of the working day). In addition, the shape of the cutting tooth and the pitch of the chain make a significant contribution to productivity.

Some manufacturers indicate the cutting speed in the product data sheet. However, it is always necessary to remember that such data is very conditional, since it is impossible to calculate all cutting options with the resistance of all available materials. But there is no doubt that by informing us about such indicators, the manufacturer thereby assumes responsibility for the level of equipment operation. And, knowing the cutting speed, you can count on your chainsaw being capable of this without threatening its integrity.
Air Filter Installation

The point of having an air filter in chainsaws is that it keeps dust, sawdust and other small particles from getting into the engine and chassis. The protection system in this case is two-part: the first barrier will be the impeller mounted on the motor shaft, and the next one will be the air filter itself, nylon or felt. This element retains most contaminants and is easy to clean or replace during maintenance. It can also be impregnated with special oils that increase the capture rate of microparticles and prevent their “cementation”.
Chain brake

This function is a direct necessity based on the operating characteristics of the chainsaw: in the event of a “kickback” or accidental break of the chain, irreparable harm can be caused to the operator. Therefore, the best solution in this case is to stop the chain. It occurs through a mechanism that is activated by the chainsaw guard. If the sawyer’s hand rests on it, then through the lever the force is transferred to the brake and the chain is blocked. This can also happen automatically.