Do-it-yourself radiotelephone repair

On a cursory examination, the symptoms of both fire victims turned out to be similar, a complete refusal to start - there was no characteristic "pip" when power was applied and the inductance at the telephone line input was broken.

The problem is seemingly insoluble. But after the diagnostics (let me remind you that before that the radiotelephones were being repaired in a couple of workshops), it turned out that the 1117S power stabilizer, which powers the 3.3V processor, is to blame.

After running a couple of stores and hearing that this microcircuit is not even in the price lists and it will take a long time to wait for a new one, I bought the good old LM317. I assembled a simple stabilizer and turned it on instead of the above microcircuit.

The phone responded with a joyous "rush".

I replaced the input inductors and checked the transistors of the set - everything is fine, the radiotelephones are working.

And it became one more successfully animated device more :) Best regards, UR5RNP.

Doing something the first time is never easy. Doubts gnaw. Why take on something that you have not done before and do not know how? But on the other hand, you don't know how, because you haven't done it before. And malfunctions are not always complex. Therefore, when a friend asked to "see" his radiotelephone, LG did not refuse. He complained about the phone's operation like this - after placing the handset on the base, the charging process may or may not start. But even if the charging "went" the rechargeable battery still does not charge. Bought a new battery but nothing has changed. The first thing I did was connect the base to the network and check the voltage at its output.

Everything is fine here, almost 9 volts. Then I removed the back cover and connected the device itself to the base of the radiotelephone. I was interested in the presence of voltage at the contacts of the storage battery.

The tension was completely absent. But the search direction appeared, and it was time to look at the schematic diagram.

If you know how electronic components are indicated on schematic diagrams, then you can safely expect that after a certain amount of time viewing the circuit of the electronic device of interest, the basics of understanding how it still works or should work will appear. This is at least.

So the spark of enlightenment that appeared made it possible to continue disassembling the radiotelephone tube. On the opened back side of the board, I immediately did not like the state of the contacts circled in red.

I washed everything with alcohol, and I also irradiated those on the right. Reassembled in reverse order.

The voltage of 6 volts required for charging appeared on the battery connector. In other words, the function of charging the phone's battery has been restored. I assembled the body of the handset and, connecting the battery, measured the charge current - almost 160 mA. The battery is 3.6 V, with a capacity of 600 mA, which means that the minimum charge current is 60 mA (10% of the capacity), and the minimum voltage is somewhere around 4.8 V (U battery + 30%). In fact, both are beyond measure. Charge, the batteries should be fast. I put the battery back in place, assembled the tube and put it on the included base. After 8 hours, the phone did not work. The battery was removed from the battery compartment, which after a whole night of charging had a voltage of 1.3 volts. In the most merciless way, the new battery was disassembled into three batteries.

Only one of the three was charged - efficient. The other two were null and void. It turned out that I got two faults, superimposed on one another, and although both are simple in nature, I think I was lucky to figure it out.

And the phone worked fine when the purchased battery was put into it again. Only this time three people participated in the purchase - a multimeter and my friend and I.If you simultaneously wiggle your brains of your head and your fingers, then everything will always work out. The progress report was prepared by Babay.

An approach to troubleshooting radiotelephones in the absence of their circuit diagrams.

Since all radiotelephones are 90% composed of the same nodes (receiver, transmitter, encoder, etc.), it is possible to build a logical chain of processes that occur during their operation, based on the features of the functioning of a single-channel radiotelephone. The difference in the operation of radiotelephones relates to the control functions, which in single-channel telephones are carried out by mechanical switches, and in multichannel telephones using microcontrollers. Let's consider an example of a logical chain of processes.

Turn on the tube. From this moment until the signal of an idle line appears, the following processes take place in the database: 1) the IN USE indicator turns on; 2) the decoder of the identification system is triggered; 3) the supply voltage is supplied to the transmitter, 4) the key of the dial-up relay is turned on; 5) when dialing a number, the IN USE indicator indicates the number of dialing pulses. It is necessary to trace the sequential implementation of these processes in the base of the radiotelephone along all circuits, from the antenna to the point at which the process is disrupted. As an example, the table lists possible malfunctions of radiotelephones.

The most common defects in radiotelephones of various companies.

Consider the defects inherent in all types of radiotelephones. So, if any liquid (water, tea, coffee, etc.) gets into the tube, the following malfunctions are possible: 1) The tube does not turn on or there are no sound signals to confirm key presses 2) There is no dialing when some of the handset keys are pressed: no sound confirmation signals To eliminate faults, do the following.

Disassemble the tube and remove the board from it. Remove the flexible or rubber keyboard (depending on the design). If there is moisture on the contact pads of the board keys, or traces of oxidation or remaining traces of dried liquids of unknown origin are visible, wipe the board with a soft flannel moistened with alcohol. Do the same with the flexible keyboard and rubber keys.

After the alcohol has dried, the tube must be reassembled. With more severe oxidation effects, some conductors can be etched, which must be restored by soldering jumpers.

Another defect that occurs, as a rule, when liquid enters the base through the holes for the charging contacts, leads to a lack of charge in the handset battery. In this case, the charge indicator does not light up. To eliminate the defect, disassemble the base and inspect it and the charging contacts. There are cases of destruction of the supply conductors, as well as the printed conductors both on the base and on the charging contact board. The defect is eliminated by flushing the board with alcohol and restoring the destroyed conductors using jumpers.

Battery defects.

Very often batteries fail due to improper use of the radiotelephone. How does this happen? Many models do not have a power switch on the handset. The phone works in standby mode all the time (the handset is not at the base). After passing all the alarm levels of the battery discharge (audible and visual), the battery is discharged below the permitted level

You can check the performance of the battery using a tester. First, check the voltage value.It should be at least 3 V (if there are three cells in the battery). If it is much lower, for example 2.5 V, this indicates that one battery cell has failed. The next step is to check the presence of the battery capacity. The tester is set to the DC current measurement mode at the limit of at least 3 A. Observing the polarity, it is necessary to connect the instrument probes to the battery for a short time (1-2 s). The overshoot of the arrow of the device indicates the good quality of the battery. If the arrow deviates to 100 ,. 200 mA, then it is most likely discharged.If the defect persists after 16 hours of charging the battery, the battery must be replaced.

A defect in the radiotelephones of inexpensive models 155, 418, 4010, 4020 of the PANASONIC trademark, which manifests itself as a lack of communication between the handset and the base.

The defect can be caused by a detuning of the FM detector contour in the tube due to mechanical impact on it (hitting the floor, shock, etc.). To eliminate the defect, disassemble the tube, remove the board and apply a flexible film of keys or a rubber keyboard to it. Connect the battery. They encode the handset by briefly connecting the board to the charging contacts of the base. Disconnect the tube board from the base and press the tube locate button on the base. Slowly rotating the core of the FM detector circuit with a dielectric screwdriver (it is usually larger than all the others in size and has a spitz for an ordinary screwdriver) left and right, they achieve the appearance of a call signal. After determining the zone of signal disruption, by rotating the core, set it to the middle position. If this handset setting does not fix the defect, then return the FM handset detector core to its original position and repeat the operations with the base detector loop, ringing the base from the handset or turning on the telephone mode in models without Intercom.

Defects of radiotelephones models 7980, 9000 of the PANASONlC trademark.

Known design disadvantages of such radiotelephone assemblies of these models, such as a power switch and a flexible cable going to the board from the microphone and buzzer. In this case, either the pin of the transmitter power limit switch, or the loop, or the axis of the cover breaks most often. Consider two options for restoring the functionality of radiotelephones.

Option 1. Removing a broken cover if it is not possible to purchase a new one.
Disassemble the tube, solder the loop and disconnect the cover with the microphone and buzzer. Remove the mechanical parts of the pin if it is broken. In the middle of the semicircular protruding part of the cover, several holes are drilled for a microphone with a diameter of no more than 2 mm. The holes are drilled outside the semicircular part of the cover, having previously outlined the required number. The microphone, closed on all sides (except for the front) with a rubber or foam rubber damper, is glued with hot melt glue opposite the holes. A microswitch powered by a pin is soldered from the printed circuit board of the tube. Remove the lid opening button and its spring. But the place of this button is installed by some kind of miniature switch with normally open contacts. Two terminals of the microswitch are soldered to the pads of the board, to which the remote limit switch was soldered.On the positive terminal of the speaker (earpiece) of the tube, without removing the old circuit, the negative terminal of an electrolytic capacitor with a capacity of 10 μF, designed for a voltage of 10 V. a piece of wire is soldered onto the contact pad, to which the buzzer lead was previously attached.

The speaker will now perform two functions: a buzzer and a speaker (headphone). This is possible because the work of these devices is spaced in time, that is, they never work at the same time. The leads from the microphone are soldered to the same pads: the signal pads - to the signal pads, and the body pins - to the common wire pad. After the rework, the batteries will be charged in the same way as with the cover.

Option 2. Only the switch-on pin is broken, but the loop and the cover are intact.
Open the tube lid, remove the broken part of the pin, leaving only the parts that allow the lid to rotate. Remove the limit switch from the board. Remove the protective cover from the microphone compartment. In the middle of the upper part of the lid, a miniature magnet is glued and the protective lid is closed. On the printed circuit board, exactly opposite the magnet, a reed switch is glued to close the circuit when the magnet is removed. Two reed switch leads are soldered to the pads of the board, to which the remote microswitch was soldered.

Defects in SANYO radiotelephones. Lack of communication between the handset and the base.

To eliminate the defect, it is necessary to unscrew the screws on the tube cover, remove it, carefully remove the charging terminals and remove the board from the locks, pulling slightly the side walls of the tube body. Particular attention should be paid to the microphone, which is inserted into a rubber casing. It must be carefully removed from the board (first the microphone is removed from the casing, and only then the casing is removed from the board). Then, turning the board over, using a magnifying glass with 4x or 10x magnification, view the integrity of the printed conductors in the area of ​​soldering to the housing of the RF block screens (in its corners). A characteristic sign of a defect is a break in two conductors: near the soldering point of the screen corner and next to it (conductor 0.6 - 0.8 mm wide). The breaks are restored using copper conductors. This job requires great care and skill. To check the elimination of the defect, insert the battery, put the keyboard on the board and turn on the tube.

Wear of the handset power key.

The defect is restored in two ways:

1. Cut out the old conductive contact on the rubber keyboard with a blade. Pick up from old phones "rubber bands" with conductive contacts. Without gluing the contact, they check the actuation to turn on when the “penny” is pressed, and only after a positive result is the “new” contact glued to the remote area with superglue.

2. From the old flexible keyboard films, cut one contact with the adhesive around it and stick it to the board opposite the triggered contact. At the same time, a triggered contact may not be deleted.

SIEMENS cordless telephone The Gigaset 1010 handset is on a PIN code, the code is naturally unknown. we solder EEprom 24c04, read it with Poni Programmerom and look at the addresses: 27 and 28 there is the coveted PIN in an explicit form.

Panasonic KX-T9080, 9050 You can check the operation of the base and tube transmitters as follows: we make an equivalent load: We remove a 1.5v backlight lamp from an unnecessary wristwatch, solder a small piece of 50 Ohm coaxial cable to it and connect it to the RF output of the unit instead of the antenna. With a working transmitter, the light should glow brightly at 30mW.

Cordless telephone PANASONIC KX-T408 and similar.
In several devices of this type, a defect was found, the external manifestation of which was as follows: with a working battery, the handset did not react in any way to pressing the keyboard buttons. When checking with an oscilloscope, it was found that the 32, 768 kHz clock generator is working, and high voltage levels are present at the inputs 5-7 of the microcontroller instead of low ones. The reason is a break in the printed conductor connecting pin 3 of IC3 with pin 33 of the microcontroller. We measure the voltages at these terminals, which should be the same and have a level of about 3.5V. If the voltage level is low at pin 33 of the microcontroller, we connect the indicated terminals with a jumper from the MGTF wire.

As a result of increased voltage in the mains, varistors often fail. They are used for surge protection.

Apparatus Samsung CK-5341ZR.Some time after switching on (from 15 minutes to several hours), tuning starts to go away, or when switching from channel to channel, it sometimes does not capture the station. I tweaked the APCG circuit (he is the only one in the TDA8362 harness) - it did not help. I replaced the zener diode at 31 Volts (in the tuning circuit) - it did not help. I changed the TDA8362 itself - no result. Changed the memory (24C02) - it didn’t help. I wanted to change the control processor (SIM-135-2R С69540Y), but it’s too expensive. The owners were in a hurry, and the iterations were lengthy, so I filtered the low-voltage supply voltages and tuning voltage with semiconductor capacitors and changed the tuner itself. The device has not been malfunctioning for two months now. Unfortunately, I cannot specify the exact reason - either the tuner itself, or knocked down the power supply ripple setting. The fact is that before that I was repairing a Soviet TV with a built-in 55-channel remote control, and its settings were also lost, so the reason turned out to be that the electrolytic capacitor 470 μF / 25 V at 12 Volts in the MP- 3-3. The SAA1293 processor in the remote control was powered from the same voltage. The image was not affected by the loss of capacity.

Panasonic KX-T9000, KX-T9080: The handset does not work or is making a fool, there is no connection with the base. Check the power supply to the circuit after the three-pin IC6 microcircuit, if less than normal, change it.

PANASONIC KX-TCD951: you cannot register a pipe - solder a USB flash drive in the database
LG GT-7101, SEIMENS GIGASET: segments on the indicator disappear - solder the indicator cable through thick paper (Whatman paper)
PANASONIC KX-TC1019: no connection tube-base - register the tube. The 5-digit code is indicated on the paper label (in the base, short-circuit R909 next to the process and apply power, press 2.7, # on the pipe and apply power, dial the code. If everything is OK, the pipe goes into conversation mode)
PANASONIC-and with a lever on the base at the charging contacts: no charging or matching - solder the contacts by removing the springs
LG GT-7320: it is impossible to exit the Direct Call mode - there is an inaccuracy in the instructions in Russian - exit by double pressing (in 0.5 seconds) the microphone mute button
SIEMENS GIGASET, BT: no line - 2 and 5 pins are often used in the telephone jack (DOMESTIC CABLES USE 3 AND 4)
LG CT-9130 and GT-7101 use different polarity on contacts in power supplies
PRIMER, SANYO CLT, CLA: in case of failure of the reed switch, you can replace the reed switch itself with a domestic small-sized
LG GT-9130A: noises in the pipe - replacing the 3.99 MHz quartz in the pipe with quartz in a metal case can help
PANASONIC-and new models (not DECT) when the pipe enters the water under the process, a conductive blot is formed in 98% of cases

All models of Panasonic cordless phones type 408, the connection between the handset and the base is lost due to the following reasons:
1. Large ripple of BP. and because of this, the handset does not exchange the PIN code with the base. The malfunction is eliminated by replacing the 470 Mkf capacitor with 1000 Mkf and more in B.P.
2. Failure of the zener diode in the tube charging circuit, the batteries are charged to an overestimated voltage and the tube with the base does not exchange a security code (PIN-code).
3. Do not exchange PIN-code due to dirty contacts on the charger base or due to mechanical damage to these contacts.
4. The filters in the radio channels of the base and the tube are upset. Many tuning methods have been described if normal frequency analyzers are not available. I suggest another one, for those models that have a Speaker button on the base. If you put the handset on the base, press this button on the base, and then pick up the handset, the algorithm for connecting the handset to the base will be performed. But when the radio channels are out of tune, the passage of speech signals is not audible. It remains in this position to adjust the filters and achieve the passage of both voice and telephone signals.

If the company radiotelephones Panasonic KX-T9080 or similar ones (hinged lid) there were problems: the stem broke or the lid broke, then it can be modified with the help of a simple device assembled on a K561LN2 microcircuit. This is the most original and simple solution to the problem that I have come across. The device is easy to assemble, it works very well, it never fails. The lid and stem can be bought, the price of the complete lid (lid, cable, microphone, bell) costs about 1000 rubles, the salumin stem will cost 300 rubles. Very often you meet clients who refuse to replace expensive components. And you are losing money and a customer.

In these phones, the call can replace the actual earpiece. With the help of a fluoroplastic wire, it is necessary to connect the negative terminal of the capacitor C40 (it is the decoupling between the generator of the bell circuit and the emitter itself located in the phone cover) with the contact P of the headphone, in Figure 1 there is a red dot.

2. Scheme replacing the S2 button (this button turns on the handset when the cover is opened)

The diagram in Figure 2 is assembled on the K561LN2 microcircuit. Moreover, only the 14th part of the microcircuit is used. Electrolytic capacitor C1 47 MKF from 6, 3 to 16 volts. used in the circuit should be small, for ease of placement in the tube body. Resistors of the SMD type are mounted directly on the microcircuit. The S3 button is a button to temporarily mute the microphone. The tracks from the button to the circuitry of the phone need to be cut. The places where the tracks are cut are shown in Figure 3 with red crosses.

Leg 7 of the microcircuit must be connected to the body of the telephone circuit in any convenient place. Leg 14 of the microcircuit must be connected to a switch that turns off the telephone receiver Figure 5, the connection point is shown with a red dot.

The old microphone can be used, which must be removed from the socket in the cover. You can fix it in the hole that remains in the tube body from the stem. Observe the polarity when wiring the microphone. The negative side of the microphone is connected to its body.Figure 6 shows the microphone connection points.

Figure 6 shows the connection point for tap S2, see diagram.

You need to place the switch circuit under the phone board in the area of ​​the headphone. The scheme does not require any additional settings.

3. How the modified tube works. When you receive a call on the handset or, if necessary, make a call, you must press with your thumb on the button that previously performed the function of mute the microphone. After the end of the conversation, the button must be pressed again. The handset will go into standby mode.

This refinement has been tested on several models of Panasonic phones. For two months, not a single complaint has been received from the owners of the converted devices.

We are still waiting for similar letters from you, with personal experience in the repair of household appliances
Dimon

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Malfunction manifestation: weak light of the indicator, a message about a bad battery, although it is fully charged. Defect in diode D1 according to the scheme. How to find: check the presence of 5.5 volts at the anode, the voltage at the cathode should be 5.2 volts. If the cathode voltage is below 4 volts, then the diode must be replaced.

2). "PANASONIC" models 3611, 3621.

The following defect is observed: There is no connection between the tube and the base - the reason for this is the poorly soldered lead of the transmitter quartz in the tube.

3). In the answering machine “PANASONIC” model 4311.

During normal operation of the tube and base, there are malfunctions in the operation of the AO - the cause is increased pulsations of the power supply unit.

4). Panasonic 9080 and the like.

During operation, a crackling sound is heard that disappears (for a while) after being hit or disassembled. Reason: poor contact in the connector between the RF unit and the board.
Repair: 1). each pin of the connector is carefully rotated 90 degrees.
2). we solder the connector and solder in place of its pieces of tinned wire

To change the TONE PULSE mode, press the following key combination.
1 PROGRAM
2 AUTO
3 to select PULSE mode press # 2 times
to select TONE mode, press * 2 times
4 PROGRAM

The handset does not work, while there is a keyboard interrogation - the Zener diode D17 flew out on the mx power supply;

КХ-ТС900 and similar ones: the radius of action has become small - the filter "leaks" at 903 MHz in the tube;

KX-T9500: unstable connection tube-base, and the base-tube is excellent - the noise detector in the tube is playing pranks. Treatment - filter replacement at 455KHz; / p>

KX-T7980, 9050, 9080, 9280: there is no tube-base connection due to the drift of the transmitter or receiver frequencies (a frequent defect in 3-4 year old devices) - the trimmer capacitors in the HF unit have oxidized;

KX-TC408 and the like: it is impossible to adjust the frequency of the transmitter - you need to replace the varicap.

You can check the operation of the base and tube transmitters as follows: we make an equivalent load: We remove a 1.5v backlight lamp from an unnecessary wristwatch, solder a small piece of 50 Ohm coaxial cable to it and connect it to the RF output of the unit instead of the antenna. With a working transmitter, the light should glow brightly at 30mW.

eight). Defect in Panasonic KX-T9050, KX-T9080.

There is no or unstable connection between the base and the handset. I recommend setting up RF blocks, this is done as follows:

Handset: We solder the jumper to enter the test mode, press the Pause button (noise is heard in the speaker). By rotating the TX and RX trimming capacitors, set the voltage to 1.8v at the VXO control points for TX and RX, respectively. For this operation, it is desirable to have a repair cable, but you can do without it by soldering to the control points with a short piece of wire (the control points are on the bottom side of the RF block). It is convenient to monitor the voltage with an oscilloscope 0.5v / div. The setting is quite “sharp”; it is necessary to rotate the trimmers with a dielectric screwdriver. I use screwdrivers made from a strip of fiberglass with foil removed and sharpened accordingly. It is also helpful to tune the 12.800 MHz reference oscillator. We connect the base to tel.lines, we establish communication, with an oscilloscope we look at the signal at the output of the tube discriminator - 400Hz. - line tone. By rotating the trimmer, we achieve the maximum undistorted signal amplitude. By adjusting the discriminator contour, we achieve the same. Base: Configurable in the same way. To enter the test mode, three contractors are short-circuited. point, then power is supplied. Tighten all the screws in the RF units well before adjusting.

Fault: very quiet audibility of the subscriber in the receiver. The connection between the handset and the base is established normally and the signal from the microphone of the handset, in intercom mode, is heard on the base normally. Determining, in this case, where the malfunction is in the handset and base is very simple. Suppose you have a handset and a base connected to each other (in the same intercom mode), at this moment it is necessary to de-energize the base (remove the base power supply from the socket) and if you hear a loud noise in the handset, then the malfunction must be looked for in the base. In addition, indirectly, loud clicks from its speaker when you dial a number indicate that the handset is working properly. My malfunction was caused by poor metallization of the via in the base, between components R27, C11 (15th pin of IC4). By lightly pressing on the board with a screwdriver, it was possible to localize the malfunction.

Fault: there is no connection between the handset and the base. As I was told, instead of 4.5V, they connected 12V to the tube. But the tube turns on and looks for the base. As a result, only the transistor assemblies Q14 and Q15, as well as the diode D13, turned out to be faulty (i.e., no power was supplied to the RF unit).

eleven). All Panasonic KX-T7980 radiotelephones. 9080.

Fault: during a conversation and at the same time when you move, unpleasant rustles are heard in the receiver. The antenna turned out to be faulty (it was necessary to pick less in the ear). The antenna “spring” is inserted into the brass adapter; on the other side, a plate with a hole is inserted into the adapter. It is necessary to move the antenna and if you hear rustles in the tube, then you just need to squeeze this adapter, but not much, otherwise it may burst. If it does burst (or compression does not help), then it just needs to be properly soldered.

thirteen). Panasonic KX-T9000, KX-T9080.

The tube does not work or is making a fool, there is no connection with the base. Check the power supply to the circuit after the three-pin IC6 microcircuit, if less than normal, change it.

14). All models of Panasonic cordless telephones type 408.

The handset loses connection with the base due to the following reasons:
1. Large ripple of BP. and because of this, the handset does not exchange the PIN code with the base. The malfunction is eliminated by replacing the 470 Mkf capacitor with 1000 Mkf and more in B.P.
2. Failure of the Zener diode in the tube charging circuit, the batteries are charged to overvoltage and the tube with the base does not exchange a security code (PIN code).
3. Do not exchange PIN-code due to dirty contacts on the charger base or due to mechanical damage to these contacts.
4. The filters in the radio channels of the base and the tube are upset. Many tuning methods have been described if normal frequency analyzers are not available. I suggest another one, for those models that have a Speaker button on the base. If you put the handset on the base, press this button on the base, and then pick up the handset, the algorithm for connecting the handset to the base will be performed. But when the radio channels are out of tune, the passage of speech signals is not audible. It remains in this position to adjust the filters and achieve the passage of both voice and telephone signals.

The connection between the tube and the base is lost. A defect in the contact group of the charge at the base, - (the contacts are connected to the tube through a spring-loaded switch ?!). During operation, the connection fails and of course the PIN code. It's hard to understand right away!

The radius of action of 1.5-2 meters has greatly decreased. A faint noise is heard in the handset when establishing a connection, even at a short distance. Calculated that there is a malfunction in the tube (in the radio receiving path). Usually, the RF amplifier is to blame for the decrease in sensitivity (it knocks out a field-effect transistor (in Panas most often) or a bipolar transistor (this is what it stands here).Replacing the transistor did not give any result. Further - only m / s TB31224F- 1st mixer, 1st local oscillator, 2nd mixer, etc. before the demodulated signal. Since it is problematic to replace it, I tried to replace the 455 kHz filter. The problem turned out to be in him.

During the repair process, I encountered a tube malfunction, the processor does not start and does not respond to button presses. It turned out that the diode D15 was flashing from the battery to the charging mark. As a result, Q15 opens and the tube thinks that it is on the base. The dialing tester does not leak. Thus, I restored 3 devices.

The range drops, then first of all it is necessary to check the bandpass filter in the tube (item designation FL405). It is almost 100% dead.

nineteen). Panasonic KX-T9050B, KX-T9080BX, KX-T9000, KX-T9100, KX-T9200, KX-T9150, KX-T9250.

Sign: Noise during conversation. Cause: When the battery is discharged, the voltage changes, which causes noise in the tube. Elimination. Change the resistance value R87 6.8kOm to 12kOm.
Panasonic technical support service.

twenty). After the breakdown of the shutdown mechanism (handsets of the Panasonic 7980 telephone and the like).

Structurally aligned with the axis of the hinged cover, after analyzing the circuit diagram of the tube, I used a conventional reed switch with normally open contacts to control the tube. I placed the reed switch in the area of ​​the tube LEDs under the board, fixing it to the light guide so that its axis was along the tube. In this position, the reed switch is most sensitive to the magnet, which is located at the end of the hinged cover. I used a magnet rectangular from a magnetic furniture latch, it did not need to be reworked. The standard switch is shorted with a drop of solder. One end of the reed switch is connected to the common wire (-), the second to the 60th leg of the processor (it is better to solder to R105, which can be found on the left edge of the board: one of the contacts of the standard switch is connected to two resistors, one (R49) to the common wire, another (required R105) to D18 and 60th leg of the processor). When the tube cover is closed, the reed switch provides a low level at the 60th leg of the processor corresponding to the CLOSE mode.

21). PANASONIC KX-T408 radiotelephone and similar.

In several devices of this type, a defect was found, the external manifestation of which was as follows: with a working battery, the handset did not react in any way to pressing the keyboard buttons. When checking with an oscilloscope, it was found that the 32, 768 kHz clock generator is working, and high voltage levels are present at the inputs 5-7 of the microcontroller instead of low ones. The reason is a break in the printed conductor connecting pin 3 of IC3 with pin 33 of the microcontroller. We measure the voltages at these terminals, which should be the same and have a level of about 3.5V. If the voltage level is low at pin 33 of the microcontroller, we connect the indicated terminals with a jumper from the MGTF wire.

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Repair of a radiotelephone - We will talk about those malfunctions that can be eliminated even by a non-specialist, having detailed instructions. And you can find them here.

Hello dear visitors. In this post I will try to tell you in detail what you can do at home in order to bring back such a “toy” as a radiotelephone to life. Everything will be based on the example of the Panasonic radiotelephone, but other brands will be similar in many respects.

Of course, when it comes to the breakdown of the electronic part, this is the lot of specialists, but most often what fails is what many can do on their own, we read about how and what to do and look below.

One of the common malfunctions of radiotelephones after prolonged use is that some buttons, when pressed, stop working at all or require a lot of effort.

Usually this happens with those buttons that are pressed most often, they can be easily identified by wear.This malfunction is akin to the same problem as in remote controls. And therefore it is eliminated in the same way.

But just do not think that it is enough to clean, rinse and that's it. This method is very widely described, but believe my many years of experience in the field of repairing remotes, it does not help for long, in 90% of cases for a week. For a quality repair, you will need to purchase something in advance, but more on that below.

Any repair begins with disassembly.

When disassembling an unfamiliar device, there is no need to rush, be careful, try to memorize and, if necessary, write down / photograph / mark some nuances, for example, even the mounting bolts can be of different lengths in different places and they must not be confused. Mindfulness will help you put everything in place without error and you will not have any unnecessary parts.

But in this case, everything has already been described and photographed. Begin!

The owner of the phone complains that he stopped turning on, the reason is trivial, the buttons do not work. The photo clearly shows that the power and reset buttons are heavily worn out.

After removing the batteries, we find the fastening screws in the case and unscrew.

With a short and better not very sharp knife, you can also use an unnecessary plastic card or something else like that, open the phone by applying a slight force downward and to the side to unclench the latches, we try not to break them.

We pay attention to the wires, they do not need to be unsoldered, but you also don’t need to tear them off.

The next step is to find all the screws securing the board and unscrew them.

And here are the nuances, we pay attention to how these metal terminals are installed.

Well, we got there, it's not difficult at all.

Separate the rubber mat with buttons from the board.

The board itself, the part that was under the rubber band, neatly with a cotton pad dipped in alcohol (you have to drive it to the pharmacy 🙂), wipe it from fat and other contaminants. Without fanaticism, there is no need to try to erase these black graphite conductors in the form of stars and other shapes. There were cases where sandpaper was used. We carry the gum itself under the tap and in warm water with soap with a cotton swab, or better with an old toothbrush, carefully wash and dry.

When everything is ready, the gum is washed and dried, we proceed to the repair. And here, for a high-quality repair, we need a repair kit for the remotes, you can buy it in stores with a radio engineering bias. The cost is usually no more than 100 rubles. A little later I'll tell you about alternative methods.

This is what this repair kit looks like.

The material on the repair of the radiotelephone was filmed some time ago and now I cannot understand where the frames with the restoration of these buttons have gone. Therefore, I will show this whole simple process on an elastic band from the remote control. The essence is absolutely the same ... .. Apply glue to the buttons that need to be restored.

When all the necessary buttons have been glued in this way, we can start assembling. Already after 20 -30 minutes you can safely use it, but you can check it right away. As you can see, the phone turned on, the buttons work easily.

If it is not possible to purchase a repair kit for the remotes, then you can do the following.

1) Find some foil, but only the one that is paper-based, such is used in cigarette packs. Cut small pieces with scissors so that they stick to the button without going beyond its size, if anything, just press down the piece of foil planted on the glue so that it squeezes down with its edges. Use either silicone glue, or one that is capable of glueing rubber, such as a moment, rubber, etc.

• Never use super adhesives in this matter (those in small tubes quickly freeze and glue your fingers wonderfully) When they freeze, they become brittle, and when you press the button, it bends and this glue begins to crumble, as a result everything can fall off.
• Never use foil without a paper backing, it will also fall off

2) Perhaps there is some old faulty remote control, calculator.There, too, the same buttons are used, you need to carefully, thinly, cut off the desired layer with a blade in order to glue it where it is most needed.

These are standby options that can be applied, but it is better to find a repair kit.

Well, for dessert! Cordless phones are usually powered by batteries that are charged from the base connected to the network via an adapter.

This chain, Battery - Base - Adapter, is another weak link.

Therefore, if your radiotelephone has stopped charging, pay attention to it. The contacts on the base, handset and battery compartment must be clean and free from oxidation.

Make sure that the power adapter is working properly, you need to measure the voltage at its output, it must match the adapter's parameters. You will need a multimeter for this. Often a wire breaks in adapters and this is not noticeable, the break is hidden under the outer insulation. How to find out the parameters and choose the power adapter can be found here.

By measuring the voltage at the contacts of the base, those with which the tube is connected when it is in it, we can make sure that the power circuit in the base itself is working properly, the battery is charged through these contacts. If, with a working adapter, there is no voltage on these contacts, then the malfunction may be in it, in the base.

If the voltage comes out of the base unit, it should be equal to the total voltage of the batteries or slightly more. But the batteries do not charge, the reason is in the batteries themselves. There is also a small percentage of electronics malfunction in the phone board, there may be a charge controller, but this is for specialists.

You can check the batteries, for example, by substituting ordinary batteries in the handset instead. This is only true if the phone uses batteries of the same size. In some models, a block of several batteries assembled in one package may be used.

In this case, you will need to purchase a new battery of this type or an analogue.

That's probably all. Thank you for your interest in this project.