Printer is a commonly used office equipment, which mainly includes needle printers, inkjet printers, laser printers and so on. At the same time, the printer is also a kind of office equipment that is prone to failure, and the maintenance of the printer is, in the final analysis, the maintenance of its damaged parts. Therefore, it is undoubtedly of great significance to understand and master the detection and maintenance of various parts of the printer. Below I will introduce the detection and maintenance methods and skills of common printer components, hoping to be helpful to everyone's maintenance of printers.
I. Maintenance of the stylus printer
When the stylus printer has a line leakage fault, it is mostly due to the broken needle of the printhead. You can clean the needle outlet with anhydrous alcohol. If there is any empty needle position, it is mostly caused by broken needle. If there is no needle position, it is caused by other faults, such as broken signal line, burned printing needle coil or blocked printing needle guide hole. After the broken needle appears, you can replace it and continue to use it.
1. methods for changing the needles of several general-purpose needle printers
(1) LQ-19k/LQ-16k Ⅲ/LQ-16k k4 print heads
LQ-19k/LQ-16k Ⅲ/LQ-16k k4 print heads have a double-layer needle arrangement structure. The 24 needles of the print head are arranged in odd and even rows. Seen from the end of the guide plate in front of the print head, the left column is odd and the right column is even. The long needles are: 2, 6, 1, 14, 18, 22, 3, 7, 11, 15, 19, 23; Short needles are: 4, 8, 12, 16, 2, 24, 1, 5, 9, 13, 17, 21.
firstly, use the broken needle test program of the print head to check which needles are out of order, then cut off the power supply of the printer, remove the ribbon box, use the crosshead screwdriver to remove the two fixing screws of the print head, pinch the heat sink (i.e. the housing) of the print head from both sides, gently lift the print head upward to see the two flexible flat cables connected, and then pull off the cables to take out the print head. Scrub the ink stain in front of the print head with an alcohol cotton ball to see if there is any needle shortage.
if there is a broken needle, it needs to be replaced. Tools should be prepared before changing needles, mainly including tweezers, blades, diamond files, steel ruler, oilstone and special fixture for print head (a tool specially used to remove the heat sink of print head). First, use a crosshead screwdriver to remove the two screws fixing the printing needle sleeve and the heat sink, and then use a special tool to remove the heat sink. You can see that the printing head has several layers of structure, and then change the needles in the following order:
1) Put the head of the printing head down, pick up the triangular claw that fixes the upper and lower layers of printing needles, and take off the top back copper cover, then you can see 12 long needles distributed in a circle, and distinguish the broken needles from the test results. If there are still short needles broken, all the long needles should be taken out, and then the blade should be separated along the lower part of the yellow copper gasket in the middle to expose 12 short needles, and the broken needles should be taken out in the same way. Then take a good needle from the print head (whether to take a long needle or a short needle depends on the broken needle), then accurately measure the length of the needle with a steel ruler, grind the new needle with a diamond file according to the measured size (pay attention to grinding off the burr on the head of the needle), and then insert it from the original position. After replacement, gently press the tails of the 12 needles by hand to make the needles stick out from the guide plate in front of the print head. At this time, you should see that there are needles exposed at the positions of No.1 needle and No.24 needle, and there should be a hole between the needles in each column. If there is any wrong position, it must be readjusted. At the same time, when the finger is released, each needle can be withdrawn immediately, ensuring that the needles of each needle are unblocked. Close the copper seat again, and be careful that the locating pin of each needle must fall into its groove before closing the copper seat.
2) after confirming that all the short needles are in place, press the upper coil holder (that is, the long needle coil holder) together with the base (copper holder), and apply a set of DC voltages of +1V to the driving coils of each group of printing needles respectively (the power-on time should be short, generally less than 1 second, which is equivalent to applying a pulse voltage to the coils), so as to test the flexibility of each printing needle and the consistency of flying distance. In order to avoid rework after installing the upper printing needle (long needle group).
3) Install the upper needle in the original order. Install the positioning hole of the long needle layer together with the coil holder, and then install the long needle after checking that there is no gap on the side. The long needle only needs to be inserted according to the corresponding hole position. Long needles go through several guide slots from the tail to the head, and the top slot is easy to insert. The second slot is slightly more difficult. As long as you pass through it, the printing needle can go down with the trend, and it is easy to reach the position. Similarly, press the tails of 12 needles with your fingers, and the needles should lean out of the lmm from the guide plate in front of the printing head, indicating that the replaced needles are good. After all insertion, check that the locating pin of each long needle must fall into its groove, and then close the rear copper cover. At this time, it should be seamless from the side. Finally, install the triangular claw, put on the heat sink, check the long needle group with +1V power supply according to the test method of short needle group, and then install it on the original printer for testing.
before the test, do not install the ribbon, and print a single sheet of paper after the power-on self-test to prevent the ribbon from hanging on the new needle. Then use the print head broken needle test program to test it, and it can be put into use after it is confirmed to be normal.
(2) print heads of Ar-32/Ar-32II/Cr-324II
The print heads of the three needle printers are basically the same in structure, except that the elasticity of the return spring of the printing needle and the resistance of the driving coil of the printing needle are different.
the method of checking broken needles is the same as the above-mentioned EPSON LQ series print heads. Needle changing is carried out according to the following steps:
1) Put the head of the printing head down, remove the black plastic casing of the printing head, remove a movable I-shaped backing plate, then break two metal fixing clips by hand, and then remove the back cover plate, the pressing reed of the printing needle armature and the white plastic bracket in turn. At this time, you can see the armatures of 24 printing needles in a circular arrangement.
2) Take out the broken needle with tweezers (when taking out the broken needle with tweezers, do not take out the nylon pin and the return spring under the printing needle), and also take down a good printing needle from the printing head, accurately measure the length of the needle with a rigid ruler, grind the new needle according to the measured size, deburr the needle head with a diamond file, then insert it from the original position, and gently press the armatures of 24 needles with your fingers.
3) put back the white plastic bracket, the pressing reed of the printing needle armature, the back cover plate and the fixing clip in the original order, then put on the print head housing, and apply a set of DC voltage of +1V to the driving coils of each group of printing needles (the method is the same as LQ series print heads), and test the flexibility of each printing needle and the consistency of flying distance in turn.
4) put the print head back on the original printer, print a single sheet of paper by self-checking without installing the ribbon (to prevent the newly installed print needle from hanging up the ribbon), then use the print head broken needle test program to test it, and it can be used after it is checked to be normal.
2. Troubleshooting of the printing needle coil
Another common fault of the printing head is the damage of the driving coil. The method to determine whether the drive coil is damaged is to insert one end of a print head cable into the print head, and measure the DC resistance of the corresponding drive coil at the other end with a multimeter. Generally, the DC resistance of the drive coil should be 33 Ω? 2 Ω, if the deviation of the measured resistance is large, it may be that the coil is open or short-circuited, which will cause the needle to fail or the needle is weak. When testing, one probe of the multimeter can be connected to the male terminal, and the other probe can be connected to the corresponding point of each driving coil. When replacing a single coil, the solder on the coil can be removed with a tin absorber first, and then the surrounding glue can be cut off with a blade, and the single coil can be removed and replaced.
most of the reasons for the open circuit failure of the print drive coil are the damage of the print needle drive tube on the motherboard. The short circuit of the driving tube will cause the driving current to be too large and the driving coil will be burned out. To judge whether the driving tube is faulty, use multimeter to measure the print head cable: the red stylus is connected to the male terminal (the male terminal is the positive electrode of the driving power supply), and the black stylus is connected to each corresponding position of the driving tube. Under normal conditions, the measured DC resistance should be about 18 kiloohms. If the deviation is large, it means that the driving tube has been damaged. Each drive tube corresponds to? For example, there are 24 driving tubes Q1~Q24 on the motherboard of LQl6K printer, which correspond to 1? Print needle number 24.
3. Print head cable failure
The connecting cable of the print head in general needle printer generally adopts plastic flexible ribbon cable (flat cable). The fault of print head cable is generally checked by the electric block of multimeter. The method is to put two probes of the multimeter on the corresponding lines at both ends of the cable to measure whether the resistance value is zero, and if necessary, do a bending test at the crease to observe whether the resistance value measured on the multimeter changes. Once the cable is diagnosed as broken, it must be replaced with the same print head cable, and the broken part cannot be treated by welding. Otherwise, a slight carelessness in the use process will cause a signal short circuit, and in serious cases, it will lead to a signal short circuit to the ground (frame), resulting in a failure of the main control circuit of the stylus printer
When the print head cable is creased but not broken, a piece of adhesive tape of about 1.5cm can be intercepted, and then a piece of adhesive tape with a length of about .5cm and a width can be used. Then bend the cable slightly outward at the crease, align the paper with the crease, and stick the tape to the cable. In this way, the tension generated by the adhesive tape sheet will always force the cable to bend slightly outward at the crease, so that the cable can generate an appropriate outward tension at the crease, which can reliably prevent the cable from folding at the crease caused by the right movement of the print head in the printing process and prevent the signal line in the print head cable from breaking.
II. Troubleshooting of the carriage
Under normal circumstances, the carriage in the carriage mechanism of the stylus printer should be smooth and stable, so that after the printer is turned on, no matter where the carriage is, it can return to the initial position at the left end, and the carriage carries the print head back and forth when the printer works. If the font car fails, the print head will not move in place or not at all, resulting in the failure to complete the printing work.
generally, the inspection sequence of the carriage is as follows: printer carriage mechanism (mechanical failure)-carriage motor (resistance and torque of each phase coil)-resistance value of carriage motor drive output socket (positive and negative resistance)-carriage motor drive power supply voltage-ground resistance of input and output terminals of drive circuit-carriage motor phase control circuit.
There are mainly the following types of troubles of the word carriage:
1. There is too much dirt in the word carriage mechanism, which often causes the word carriage to fail to return to its place smoothly. At this time, the trouble can be eliminated by cleaning.
2. even the mechanical failure of the carriage mechanism, such as the abrasion of the carriage belt, the displacement of the parallelism of the front and rear guide rails, etc., will also make the carriage unable to return and move smoothly. In this case, only the belt or guide rail of the carriage can be replaced.
3, word car motor fault
Byte motor itself fault is mainly that one or more windings of stepping motor are burnt out (short circuit, open circuit). This kind of fault can be judged by directly measuring the DC resistance of motor coil windings with multimeter and then comparing it with the normal resistance (generally speaking, all four windings of motor will not be burnt out, but one or more windings are always good). If one or two phases of the motor coil are burnt out, as long as the coil skeleton is not deformed (the rotating shaft rotated by hand has no obvious jamming), it can be fired by itself according to the original wire diameter and turns of the motor (when disassembling the burnt coil, pay attention to counting the turns, and then measure the wire diameter with a fractional card); If the bobbin of the motor has been severely deformed, it should be replaced with a new motor. In addition, in the long-term use of the printer, due to vibration and other reasons, the magnetic steel in the motor may be demagnetized, resulting in insufficient rotating torque of the motor, which makes it difficult for the printer to move during printing. In this case, a new motor of the same model should be replaced.
4. Switching circuit failure
For the adoption of? High-voltage drive low-voltage locking? For printers in the motor drive system of word cars, such as printers such as AR-324, AR-2463, AR-32, LQ-15, LQ-8/1, it is often the case that the triode c~e supplying high voltage in the high/low voltage switching circuit breaks down or opens. If the c~e electrode breaks down, the driving high voltage will always be applied to the winding of the stepping motor, which may further cause the winding of the motor to burn out and burn out the triode used as the phase signal for driving the stepping motor. If there is an open circuit between c~e poles, high voltage cannot be supplied to the motor of the carriage, and the carriage will not move if the motor does not operate.
in addition, there may be a fault in the control signal part of high/low voltage switching. At this time, it should be detected and eliminated according to the circuit of the specific printer model.
5. phase-missing fault of the carriage motor
after the printer is powered on, if one or two groups of four-phase windings of the carriage stepping motor are open, the carriage will shake in its original position or be weak, or even the carriage will not move. This phenomenon may be caused by poor contact or disconnection of the plug of the word car motor, or by the failure of the phase control part in the control and drive circuit of the word car motor. Because the circuits of various printers are different, it is necessary to analyze and test the specific circuits, find out the fault points and eliminate them.
6. The stepper motor driver or its peripheral components are damaged
The stepper motor driver is a triode or ASIC used by some printers to control and drive the word carriage motor. For example, in AR-324 printer and M-2724 printer, the word carriage stepping motor uses transistors D1579 and D1789 as their respective word carriage motor drivers, while in DLQ-2K,AR-44 and CR-324 printer, SLA726M is used as the word carriage motor driver. If these devices are damaged, the word carriage will not work normally. Only by replacing the damaged components can the fault be eliminated.
7. special gate array circuit failure of the word car motor drive circuit
the CPU controls the word car motor drive circuit through special gate array circuit (such as E5A9BA in LQ-16K printer) or I/O interface circuit (such as E5A24GA in DLQ-2K printer and XBL-2 in AR-32 printer). If this part of the circuit is damaged, it will affect the normal operation of the font car, even when the printer is powered on, the font car will not return to its original position.