DIY usb modem repair

In detail: do-it-yourself usb modem repair from a real master for the site my.housecope.com.

Typically, in the elementary school curriculum, children are taught to first find the root of a word. However, this approach is incorrect, as it leads to possible errors in the search for morphemes in a word. The sequence of actions should be as follows:

1. Determine the part of speech to which the word belongs. It is important to do this right away. For example, if the token is immutable, there will be no ending. Also, do not be lazy to remember the features of the formation of this type of tokens.

2. Next, find the ending. To do this, you need to select the maximum number of options with different endings, and then graphically highlight the ending.

3. Mark the existing suffixes and postfixes, which are always preceded by the ending. Do not forget that the same parts of speech are often formed according to the same model and have the same formative suffixes, of which there can be more than two.

4. If you have followed the two previous steps correctly, then determining the stem of a word will not be difficult. Select the base graphically, highlighting all the words except the ending, since this mass is not included in the base.

5. Designate graphically the prefix (prefixes) of the lexeme. For the purpose of self-control, try to choose several variants of lexemes of the same part of speech with the same prefixes.

6. The last stage is the selection of the root of the word. Note that complex tokens can have two roots. In this case, do not forget to graphically indicate the connecting vowel.

For a person who does not sit still and cannot do without the Internet on his laptop, a CDMA modem is a necessary device in the user's arsenal. Usually, such modems have a USB interface, which is very convenient for use, but during operation, due to negligence, it is usually the USB plug that breaks down and it becomes necessary to repair the modem.

Video (click to play).

Repairing such a malfunction requires some "creative" approach to insert the plug back into the modem, see an example of such a repair in the pictures below. If the damage is not severe, then you can align and leave the original plug, but it is better to put a new one, which is certainly more reliable.

The article is out of date. We no longer repair 3G USB modems.

The second common problem is wear and tear on the moving parts of USB modems. Usually, the wires or ribbon that connects the plug to the device board are frayed. An example of such a malfunction and how to fix it can be seen in the pictures below.

Another type of malfunction is damage to the SIM card receiver when contacts or the entire SIM slot are broken. In this case, it is necessary to replace the sim-receiver, choosing the appropriate size and contact group.

The modem loses connection or gives out a weak network signal if the input circuits and the modem antenna are faulty, in which case it may be necessary to replace the signal amplification chip or repair the device antenna.

Unlocking the modem from the operator is necessary if you want to use the purchased modem with a sim-card of another telecom operator, which for one reason or another is more convenient for you.

Nowadays, the 3g network has become widespread, so many cellular companies produce USB modems for it, or rather, they take a well-known manufacturer, stamp a logo on the case, and install their software. Recently I got a couple of such representatives, it seems like they are not workers, but I decided to spin it up, see what's what and, if possible, restore and unlock it.

The first device was from the famous yellow striped brand Beeline.The modem was very common once, it can be safely used now, a couple of minutes with the instrument and we see the filling of the whistle device - the modem was clearly drowned in something sweet, such as tea - after cleaning a little and testing it, I understand that there is absolutely no way to revive it, since it does not respond to commands at all and is not detected by the port in any way, it seems that the controller responsible for the usb port has died and the treatment of such a patient becomes unprofitable.

Although you can see a photo of the insides - it may come in handy during disassembly and assembly so that everything is done in detail.

The next device turned out to be a modem from the also very famous operator Megafon, then I had to sweat to unscrew the screws - too narrow non-standard edges turned out to be.

Having disassembled and cleaned (judging by the oxides, just rain-type water got in) and heated a couple of straps, cleaned the connectors with a solvent, and then managed to start the whistle with alcohol!

The antenna, judging by the size, is larger here, and it sits firmly - besides, this device can be easily sewn and unlocked with simple manipulations, so a lot of interesting things can be done with the worker in software.

The LED in the smd case turned out to be very bright and clear, the device works quite clearly.

At the moment when I wrote comments on the articles of the Mozhochin, I literally lost the Internet in mid-sentence. First of all, I went to look at the modem, where I found out that it was finished - not a single LED was on. After thinking a little, it was decided that there was nothing to lose (the guarantee was over long ago), and the autopsy no longer scares me.

This article is more of a success than a natural victory over a breakdown, but still. I am a person a little distant from delicate electronics, but I can distinguish a burnt look. Therefore, having disassembled this device

the following picture was presented to the light white:

After careful sniffing and inspection, the gaze settled on this condenser.

Its shape changed markedly, although there was no gap. The marking informs that its capacity is 3300μF and voltage is 16V. Since I don't have an LC meter, I continued examining it with a multimeter and measuring its resistance. So it interested me. The charge was taken very reluctantly, and the increase in resistance quickly stopped.

After that, two Soviet capacitors, with a total capacity of almost half of the original, were pulled out of some frames.

After connecting one capacitor in parallel, the power LED showed signs of life, which meant the correct course of my thoughts. Having soldered the second one, I tried to turn on the modem - and, lo and behold, the Internet started working! Therefore, I can write this article!

Now it remains to spend $ 0.5 to buy the original capacitor, and 10 minutes of time to assemble everything in a bunch! Of course, this is not a detailed analysis of the modem repair, but still a description of one of its breakdowns. So if someone comes in handy - I'll be glad! :)

After purchasing a powerful soldering iron, I decided to continue the repair. Armed with a new unit, I still managed to pull out this evil condenser.

In its place, a capacitor found at work, although inferior in capacity, was hoisted.

After that, the modem blinked merrily with LEDs.

And he briskly sent a bunch of information packets through the wires. :)

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The book deals with practical issues related to the repair of personal computers at home or office.

The main malfunctions of modems

After visual inspection, turn on the power. Check if the LEDs are on. Connect the modem to the telephone line.

Immediately after connecting, the modem should not "occupy" the line.Call your landline phone number, for example, from a mobile phone.

After the ATH0 command, the modem should hang up. If the modem does not "pick up" the phone, you should check the resistor, relay, diode bridge, protective elements, key transistor, zener diode.

If the AT commands do not work, then the port chip may be replaced.

If the line supports tone dialing, you can issue the ATDTxxxxx command, or ATDPxxxxx for pulse dialing, where xxxxx is the phone number.

If the modem reported - No Dial Tone, check the zener diode, transistors, if everything is checked and correct, then the microcircuit may be out of order.

In addition, a zener diode may turn out to be faulty, which can be changed to any one with a stabilization voltage of about 9 V.

For dial-up connection, 56 K modems are used - this type of modems works with a telephone exchange in the same way as a regular telephone.

Distributed products of modem manufacturers ZyXEL, D-Link, ACORP, U.S. Robotics. Modems are available in two versions - internal and external. The internal ones are built into the computer in the same way as the sound and video cards. The modem card is installed in the PCI slot of the MP. An internal modem is also called a win modem or keypad modem.

An external modem is designed as a separate "box" and is connected to a PC using a COM or USB connector. When buying a modem, if it provides only a connection via a COM port, you need to check for the presence of a COM port in the motherboard. Many modern motherboards are no longer equipped with the outdated COM port. If you purchased a modem designed to connect to a COM port, or you still have an old modem for a COM port, and you replaced the motherboard, then purchase a special adapter for connection to connect. Typically, all dial-up modems have a built-in fax function.

One of the best, reliable and convenient programs for working with fax modem -. It only works with a dial-up connection. It does not work via ADSL modem. VentaFax is a very reliable and multifunctional program, intuitive, it has a wide range of office automation tasks.

To transfer a document, it must be converted into a graphic file using a scanner. After receiving a fax, the received file can be easily printed on the printer. A voice fax modem is used as an answering machine, telephone recording device and caller ID.

For signal transmission over long distances and better noise immunity, levels of +12 V for unity and -12 V for zero are used. Signals with such voltages are used to control external modems. In the modem, to power the microcircuits, as a rule, a voltage of 5 V is supplied, for the port to work, a level converter is turned on - special microcircuits.

An external COM modem is powered by its own power supply. The USB modem is powered via USB from a computer. External modems use LEDs (up to 8 indicators) on the front panel to indicate the current state. The decoding of the indicator messages is given in table. 14.1.

Some external modems are equipped with displays, answering machine functions and can work even when the PC is turned off, for example, at night.

Modem LED Messages

Rice. 14.1. Adapter for connecting devices with a COM connector to a USB port of a computer

There is a microcircuit inside the modem that performs two functions. This is a DAC and ADC - converting a binary code into an analog signal and vice versa. This operation is implemented by DSP (Digital Signal Processor) - a digital signal processor. The second task that the large integrated circuit of the modem performs is interaction with the PC and self-monitoring. In older modems, these two functions were split between separate microcircuits.

For galvanic isolation between the modem and the analog telephone line, transformers are installed on it - a matching unit. It is usually designed for all kinds of communication standards when using a modem in different countries.

The modems are equipped with memory chips. This is a non-volatile memory that stores the modem control firmware (firmware), which includes sets of commands and data for controlling the modem, all supported protocols and an interface with a computer. Modem firmware update is available in most modern models.

In order to provide the possibility of flashing, flash memory - ROM is used for storing firmware. It allows you to update the firmware of the modem, fixing errors of developers and expanding the capabilities of the device. Some external modem models also use it to record incoming voice and fax messages when the computer is turned off.

NVRAM is a non-volatile, electrically programmable memory that stores modem settings. The user can modify them with the AT command set.

RAM is the modem's random access memory; it is used for buffering the received and transmitted data, the operation of compression algorithms, etc.

Win-modems are deprived of ROM with firmware, in this case it is stored in the memory of the computer to which the modem is connected. It works only if the drivers are installed.

The modem dials the number using either pulse or tone dialing.

Pulse dialing is a method of dialing a telephone number, in which the digits of the dialed number are transmitted to the PBX by sequentially closing and opening the telephone line, the number of pulses corresponds to the transmitted number ("0" is transmitted in ten pulses). Pauses between numbers are encoded with a longer pause.

The signal is generated by closing the relay. It can be: electromechanical, reed switch or optoelectronic. In this case, the relay contacts can be closed to the load resistor or switched.

Tone Dialing - Dual-Tone Multi-Frequency (DTMF) is a 2-tone analog multi-frequency signal that is used to dial a telephone number.

ADSL - modem. This is a modern modem that uses a telephone line. At the same time, you can connect a regular modem (dial-up) to the same line in parallel, or make a connection, receive a fax, etc., while the ADSL modem is operating.

Such a modem usually connects to a PC via a USB port. More functional modems have and / or are connected to the connector of a PC network card, and act as a network hub. ADSL modem works on the principle of frequency division of channels. Data transmission is carried out at high frequencies, the person does not hear them.

Typically, an ADSL modem is connected to the line through a special splitter that separates the input signal into a signal from the PBX and a digital ADSL signal. In the opposite direction, the splitter adds both signals and sends them to the PBX via the telephone line. Additional telephones that are connected to the line before the splitter must be connected through a microfilter to eliminate interference from them.

Modulation Protocol - A modem communication protocol allows modems to exchange data with each other. The protocols define the order of communication establishment, modulation method, data transfer rate, interleaving of data and signaling, and also the end of a communication session.

A modern modem can work with one of the following protocols: V.92, V90, V.34, V.32bis, V.32, V.22.bis, V22, V.23, V.21, Bell 212A, Bell 103.

The MNP (Microcom Network Protocol) protocol allows for error control and other service functions supported by the modem at the hardware level, which ensures high-quality communication on noisy telephone lines.

V.90. The data transfer rate from the provider to the modem is up to 56 Kbps. This data transfer rate is available when using a digital PBX. Data transfer rate from user to provider up to 33,600 bps. In V.90 modems. V.42bis protocol (advanced MNP) is used for error correction, data compression.

V.92. The data transfer rate from the user's modem to the provider is up to 48 Kbps using the V.44 protocol for error correction and information compression. The V.44 protocol compresses data more efficiently than V.42bis. When using it, the download speed of HTML pages can reach 300 Kbps. Thanks to the V.92 protocol, the modem remembers the parameters of the line, which makes it possible to halve the connection time when redialing.

All modems provide support for older protocols. When, when trying to establish a connection, the modem cannot connect, it selects the previous protocol, respectively, the slower one.

All mobile operators that offer Internet access via the 3G network (MTS, Megafon, Beeline, etc.) have a certain coverage area. If you are behind it, your internet connection will be very weak, your connection will be unstable, and your speed will be slow. In such cases, you can use options that will enhance the signal of the 3g modem.

The first option, how to amplify the signal of a 3g modem with your own hands, which you can try at home without unnecessary waste and effort, is to use ordinary sound speakers. Mobile Internet users noted that if you move them closer to the modem, the signal level increases by 10-20%. This is not very much, but if the connection quality is poor, it gives a tangible increase. To get rid of annoying clicks from the speakers, the sound should be set to a minimum.

Another way, how to easily amplify the signal of a 3g modem with your own hands, will require you a little more action than the option with speakers. You need to make a structure of wire and a tin can, which would act as an antenna. The algorithm of actions is as follows:

Take copper wire (preferably a long piece).
Open the gadget and make 5-6 turns around the SIM card.
Pull the other end to the window.
Take a tin can or cut off the neck to create a "glass". He will act as a reflector that enhances communication.
Tie the free end of the wire to the bottom of the can.
Rotate the neck towards the direction of the nearest operator's tower. The increase in the quality of the Internet will be up to 90-95%.

Before tinkering with antennas with your own hands, you should try another method, how to enhance the signal reception of a 3g modem. Some mobile Internet users do not know that by default, when the connection quality is low, the device automatically switches to 2g communication mode, with which it is impossible to work normally. In this case, the transition occurs even in the presence of 2-3 "sticks". To avoid such situations, it should be clearly indicated through the device settings that only a 3g connection should be used. To change an option:

run the network setup program;
select the "Connection" tab (or with a similar name);
then the network search mode must be changed from automatic to 3g.

This will force the device to only operate on those frequencies, without dropping the connection to a slower speed. Some modems do not have such an item in the application interface for the device. In this case, you should look for a combination to activate the built-in command in the instructions for the device or in specialized forums. Each modem model has its own order of enabling the option.

This is not the best, but a working way to easily amplify the signal of a 3g modem with your own hands.Suitable for people who do not want to disassemble, re-solder their device. The design works on the principle of a satellite dish. To make it you need to buy a "reflector" (jar, bowl, CD), USB cable "mom-dad" 3 meters. The creation process is as follows:

In the middle of the disc, make a mount for a USB flash drive, or tape it with tape.
Connect one end of the cable to the computer and the other to the modem.
You can use a stick instead of the holder, or simply attach the disc from the street side to the front of the house.
Point the flash drive in the direction where the signal is strongest.

The increase in connection quality is not very large, because the USB cable loses some of it due to the length, but it still improves the connection. The mirror surface of the CD acts as an amplifier. It is recommended to use a bowl instead of a disc because its reflective surface is larger and the reception will be even better. Enamelled options are not suitable, use stainless steel products.

Operators are aware of communication problems, so they are constantly trying to expand the coverage area. As an intermediate solution, for example, a 3g signal amplifier was created for the Megafon modem and other companies. This is an antenna that operates at the required frequencies, and you need to connect it directly to the device. When choosing a model, you should rely on the characteristics of the radiation pattern and gain.

For effective operation of the antenna, it must be directed towards the tower of the mobile operator, which is closest to your home. Attach the stand so that the pins are perpendicular to the ground. Note that the longer the cable length, the greater the signal loss along its length. A short cord will provide sufficient connection gain, provided it is of good quality. If you bought an amplifier, then you should not save on the cable.

The most effective is amplification using a special device - a 3G repeater. Amplification is possible only if the phone picks up at least a minimal 3G signal. This approach can be called fully professional, since after installing the repeater you will receive:

maximum possible amplification of the 3G signal;
the maximum speed of the mobile Internet that a mobile operator is capable of providing;
stable reception area within the coverage radius of the internal antenna;
getting rid of problems that arise with a weak signal: disconnections, subscriber inaccessibility, interruptions during a call and others.

A repeater is an amplifier of a cellular communication and Internet signal for a summer residence, house or apartment, which in itself is only a part of the 3G signal amplification scheme. To create a full-fledged system, you will need an external antenna that picks up the cellular operator's signal from the base station and an indoor antenna that “distributes” the cellular signal to subscribers indoors. All this is commutated with a coaxial cable. In difficult cases, boosters, attenuators, splitters and other equipment may be needed. In usual cases, for example, to amplify a 3G signal in a country house or in a cottage, it is enough to buy a ready-made kit, for example, VEGATEL VT-3G-kit. This kit is optimal in terms of price / quality criterion, it works reliably and you can easily install it yourself. VEGATEL equipment is manufactured in Russia and has all the necessary certificates.

Another option, how to amplify the 3g modem signal with your own hands, is to use additional devices to connect to the internal antenna. Every such device has it, but some have an open connector, you can easily connect to it, while in others it is hidden in the case, and you will have to re-solder part of the device to use it. In the first case, you just need to buy an amplifier or use a TV antenna as a receiver.

If the connector does not exist, then you can take the device to a service center, where, for an acceptable fee, the wizard will make it possible for you to connect a repeater, which will improve communication with the nearest operator's tower.The main disadvantage of the method is that it will no longer be possible to use the modem only with an internal antenna, so you only need to decide on such a step if you know for sure that you will no longer need it.

Every summer I leave for the village with my children, but I have to go online every day. The operator's tower is far from us, so the connection speed is terrible. I made myself an additional antenna from a yusb cable, a mast and a huge bowl. The connection quality has increased by 30-40%, it could have been better if the USB cable had been a little shorter.

I am often on the road, so I use mobile internet. I noticed that sometimes the speed dropped a lot, it turned out that my modem was automatically switching to a 2g connection. After setting to use only 3g frequencies in the settings, the situation has changed for the better, although in "blind" places the connection still drops to zero.

Video (click to play).

I live in a hostel, everyone uses the Internet, so a good connection is impossible without additional devices. I used a simple copper wire, which I wrapped around the SIM card in the device, and a large shiny dish (it got from my mother). I just brought this "miracle" through the window and directed it towards the tower, the signal immediately became stronger.

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