DIY interskol repair

In detail: do-it-yourself repair of interskol memory from a real master for the site my.housecope.com.

The power section of the screwdriver charger is a power transformer of the GS-1415 type, designed for a power of 25 watts.

A reduced alternating voltage of 18V is removed from the secondary winding of the transformer, it follows on diode bridge of 4 diodes VD1-VD4 type 1N5408, through a fuse. Diode bridge . Each 1N5408 semiconductor element is rated for forward currents up to three amperes. The electrolytic capacitance C1 smooths out the ripple that appears in the circuit after the diode bridge.

Management is implemented on a micro-assembly HCF4060BE, which combines a 14-bit counter with oscillator components. It drives a bipolar transistor type S9012. It is loaded on a relay type S3-12A. Thus, a timer is schematically implemented, which turns on the relay for a time of charging the battery for about an hour. When the charger is turned on and the battery is connected, the relay contacts are in the normally open position. The HCF4060BE receives power through a 12 volt 1N4742A zener diode, because about 24 volts comes from the rectifier output.

When the "Start" button is closed, the voltage from the rectifier begins to follow to the zener diode through the resistance R6, then the stabilized voltage goes to the 16th pin of U1. The transistor S9012, which is controlled by the HCF4060BE, turns on. The voltage across the open junctions of the S9012 transistor follows the relay coil. The contacts of the latter are closed, and the battery begins to charge. The protective diode VD8 (1N4007) bypasses the relay and protects VT from a reverse voltage surge that occurs when the relay winding is de-energized. VD5 prevents the battery from discharging when the mains voltage is disconnected. With the opening of the contacts of the "Start" button, nothing will happen, because the power goes through the diode VD7 (1N4007), the Zener diode VD6 and the quenching resistor R6. Therefore, the microcircuit will receive power even after the button is released.

Video (click to play).

Replaceable typical battery from the power tool is assembled from separate series-connected nickel-cadmium Ni-Cd batteries, each 1.2 volts, so there are 12 of them. The total voltage of such a battery will be about 14.4 volts. In addition, a temperature sensor has been added to the battery pack - SA1 it is glued to one of the Ni-Cd batteries and fits snugly to it. One of the terminals of the thermostat is connected to the minus of the storage battery. The second pin is connected to a separate, third connector.

When the “Start” button is pressed, the relay closes its contacts, and the battery charging process begins. The red LED lights up. An hour later, the relay with its contacts breaks the battery charge circuit of the screwdriver. The green LED turns on and the red one goes out.

A thermal contact monitors the temperature of the battery and breaks the charging circuit if the temperature is above 45 °. If this happens before the timer circuit runs out, this indicates the presence of a "memory effect".

Over time, due to wear and tear, the "Start" button works buggy, and sometimes does not work at all. Also in my practice, the 1N4742A zener diode and HCF4060BE microcircuits took off. If the charger circuit is working properly and does not arouse suspicion, and the charge does not start, then it is necessary to check the thermal switch in the battery pack, carefully disassembling it.

The design is based on an adjustable positive voltage regulator. It allows work with a load current of up to 1.5A, which is quite enough to charge the batteries.

Alternating voltage of 13V, is removed from the secondary winding of the transformer, rectified by a diode bridge D3SBA40.At its output there is a filtering capacitor C1, which reduces the ripple of the rectified voltage. From the rectifier, a constant voltage is supplied to an integral stabilizer, the output voltage of which is set by the resistance of the resistor R4 at 14.1V (Depends on the type of battery of the screwdriver). The charging current sensor is the resistance R3, in parallel to which the trimmer R2 is connected, with the help of this resistance the level of the charging current is set, which corresponds to 0.1 of the battery capacity. At the first stage, the battery is charged with a stable current, then when the charging current becomes less than the limiting current value, the battery will be charged with a lower current to the stabilization voltage DA1.

The charging current sensor for the HL1 LED is VD2. In this case, HL1 will indicate a current of up to 50 milliamperes. If R3 is used as a current sensor, then the LED will go out at a current of 0.6A, which would be too early. The battery would not have had time to charge. This device can also be used with 6-volt batteries.

The radio amateur design is used to discharge and charge NiCd batteries with a capacity of 1.2 A * h. At its core, it is an improved typical screwdriver charger, in which a circuit is introduced that controls the additional discharge and subsequent battery charge. After connecting the battery to the charger, the process of discharging the battery with a current of 120 mA to a voltage of 10 V starts, then the battery starts charging with a current of 400 mA. The charge stops when the voltage on the screwdriver battery reaches 15.2 V or by timer after 3.5 hours (programmed in the MK firmware).

When discharged, HL1 is constantly on. During the charging process, the HL2 LED is on and the HL1 blinks at intervals of once every 5 seconds. After the end of the battery charge, upon reaching the upper voltage level, HL1 starts blinking rapidly (2 blinks with a pause of 600 ms). If the charge is interrupted by the timer, then HL1 blinks once every 600 ms. If the supply voltage has disappeared during the charging process, the timer will stop. And the PIC12F675 microcontroller receives power from the battery, through a diode, inside the transistor VT2. Firmware for MK on the link above.

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Using a 12 V lamp, you can also identify faulty circuit elements. To do this, connect a fully charged and disassembled battery to the plus and minus contacts on the 12V lamp. The load created by the lamp will be discharge the battery... Then measure the sections of the chain and identify the faulty links. Repair (restoration or replacement) can be done in two ways.

The defective element is cut off and a new one is soldered with a soldering iron. This applies to lithium ion batteries. Since it is not possible to restore their work.
Nickel - cadmium and nickel - metal - hydride cells can be recovered if an electrolyte is present that has lost volume. To do this, they are stitched with voltage, as well as enhanced current, which helps to eliminate the memory effect and increases the capacity of the element. Although it will not be possible to completely eliminate the defect.Perhaps, after a while, the malfunction will return. A much better option would be to replace the failed elements.

To repair a battery for a screwdriver, you will need spare battery, from which, you can borrow the necessary parts or purchase new chain elements. New "banks" must meet the required parameters. To replace them, you will need a soldering iron, tin, rosin, or flux.

Unsolder the connections of the defective parts and replace them with new ones. At the same time, do not allow them to overheat, which can damage the battery. To do this, try to perform quick soldering without delay. In the process of soldering, you can cool it with a touch of your hand, with the voltage disconnected.
Make the connections with native plates (maybe copper ones), otherwise overheating of the wires can trigger the necessary thermistor, which controls the heating and turns off the charging system. Remember to observe the polarity when connecting. The minus of the previous element, when connected in series, is attached to the plus of the next one.
Equalize the potential of the circuit elements. It differs in almost all "banks". To do this, put the battery to charge overnight, and then leave it to cool down for a day. Then, measure the voltage of the cells. Indicators should be very close to par.
Insert the battery into the screwdriver and give it the maximum load until it is completely discharged. Do two full discharge cycles. The result will give a complete picture of the effectiveness of the repair work.

To charge the battery device, you can make a homemade charger, USB powered... Required components for this: socket, USB charger, 10 amp fuse, necessary connectors, paint, electrical tape and tape. For this you need:

Disassemble the screwdriver into parts and cut off the upper body from the handle with a knife.
Make a hole for the fuse to the side of the handle. Connect the cable with the fuse and fit into the handle of the unit.
Fix the fuse with glue or a heat gun. Wrap the case with tape and attach the structure to the battery connector. The wires are mounted at the top of the screwdriver. The tool is assembled and wrapped with electrical tape. After that, the body is sanded, covered with paint and the resulting device is charged.

As you can see, this the process will not take long and won't be too ruinous for your family budget.

Well done kid, not every adult thinks about electrics and electronics, as they say, respect and respect for such young people, clever guys aside, the time will come to surpass you Image - DIY interskol repair

Same stuff. I unwound the strings of the piano and the charge started. disassembled the trance, - the thermo does not ring. He brought the wires past him and the fuse suddenly burned out. So the trance is whole. Climbed here to you. Help fix it. Maybe the diodes welled up?
But directly, without thermo what is impossible?

The fuse is blown again, I re-soldered the vein. But, silence in the compartments.

Are there any tensions?

+ Vladyas transistor rang. Whole.

Vryatli microcircuit burned out. If you connect to the mains voltage on the secondary winding is there? If there is, measure at the output of the diode bridge. If there is, but there is no charging, most likely the transistor that controls the relay has burned out. A microcircuit is a counter that opens the transistor for an hour.

Hello young genius)
I have a screwdriver Sturm. 8 years old to him. recently changed the old 2pcs batteries for new ones. but never charged them .. used. worked by them. and today I wanted to charge .. since they were discharged. As a result, I found out that the charging itself does not charge .. and the green light is constantly on instead of the red when I insert the battery into the charging. /What could it be. tell me pzhl.

out there. maybe this is this relay. but it does not charge without it))

The third contact is usually a thermal relay so that the Akum does not overheat

nope. I figured out everything. having disassembled your old Akum.there is some kind of small conder soldered as a third contact. here it must be unsoldered and soldered to a new one (LOGICALLY) - this turns out to be a three-pin, but there is one tin soldering and the other contact soldering to the battery. and the new batteries were sold to me like a five-hour charge without this third contact (conder). there the charger itself should be less, as I was later explained in another store. right on the fork, you can say it hangs)) in short, it is worse. as I was told compared to the old version. in the end, I was lucky to return these new Akums now. they wanted to sell me again. you said, solder the third contact from the old ones)) (as I thought logically, but did not do it) and I say that there is contact soldering)) and it will not work with tin. he tells me that do not worry, we soldered))) yeah compared. contact point soldering with tin. In short, they returned the money to me and I went and bought a new screwdriver from old stocks in another store. the same as I had. now you can say I have two of them. The new one has a 2-year warranty. I hope I told you clearly) Thank you for your attention. good luck.

You can re-solder the cover from old batteries. Although it's not entirely clear without a photo

I have a completely different matter. new batteries have completely different contacts. everything seems to fit. two big contacts. and one small on the side. and so on the new Akum there is no third contact, but on the old Akum there is. there is no charging. I bought a new charger today. for 600 rubles. like and not expensive. and came home. put it in a new charge. the same garbage .. does not charge and burns forever green. inserted old batteries everything is on .. everything works on both the new and the old charger. then I realized that the contacts were soldered. how to be I will advise

Well done, don't give up your hobby - it will help in the future!

Good boy helped a little

Good day! Please tell me from what equipment you can remove such a thermistor. My charging broke down 14.4. Thank you

If not, then you can put a jumper and everything will work.

Boy, thank you! Repair more, shoot more! Invent!

The thermistor is needed to reduce the inrush current. It is used in switching power supplies, which have large capacitors at the input, and at the moment they are turned on, they need to be quickly charged, and a large current is obtained. To avoid this, a thermistor is installed, in a cold state it has a resistance of several tens of ohms, and the capacitors are charged through the resistance of the thermistor. But when current flows through the thermistor, it heats up a little, and its resistance decreases sharply. This is how it works.
In transformer power supplies of such power, there are no large inrush currents, and a thermistor is not needed there. There is a thermal fuse inside, which burns out and breaks the circuit either when the current is exceeded or when heated. It is put on purpose, since the transformer heats up under load, and if it is loaded more than the rated power, for example, a 20 W transformer, and try to remove 30 or more from it, then there will be no conditions for the current fuse to operate, so that it needs to work, for example KZ. But an overloaded transformer will begin to heat up, up to spitting on the insulation and up to fire. It is for this reason that they put a thermal fuse inside. As soon as the transformer starts to warm up, it will work and de-energize the circuit. There will be no fire.

The kid has no difference between a thermistor and a thermal fuse. Still young.

The apparatus is exactly the same. He was already delighted.

Same stuff. I unwound the piano strings and the charging worked without rest. Then she stopped. I disassembled it. The fuse is intact, dismantled the trans does not ring the thermo. He brought the wires past him and the fuse suddenly burned out. Climbed here to you. Help fix it. Maybe the diodes welled up?
But directly, without thermo what is impossible?

fucking lucky someone with their son. and I have two girls, we sit and choose the clothes.

Vladaz, are you saying that 29 volts is the normal voltage for your screwdriver?

this charging voltage must be higher than the nominal value. Moreover, the measurement was without load under load, it will still sag.

Well, not badly filmed video. But there is nothing beyond the natural. And it's time for me to buy a multimeter and understand the reason, maybe the fuse has blown too

Cool! Good luck on the channel! 😉

Instead of a thermal fuse, a thermistor is “ingenious”

damn never fumbled in such figoviny-mechanics there electronics wiring wherever it went, but transistors resistors heat-crap all your dark forest and likes likes likes don't do it anymore because it somehow embarrasses and repels)))) but like keep- for being quick-witted. and hands grow from the right places.