Common parts maintenance methods and techniques for printers
Printers are a commonly used office equipment, which mainly include needle printers, inkjet printers, laser printers, etc. At the same time, printers are also an office equipment that is prone to failure, and repairing printers is ultimately the repair of damaged parts. Therefore, understanding and proficiency in the detection and repair of various parts of the printer will undoubtedly be of great significance to our repair work. The following is a guide to the testing and maintenance methods and techniques of common printer components. I hope it will be of some help to your printer repair work.
1. Maintenance of needle printhead
When a needle printer leaks a wire failure, it is mostly due to a needle breakage at the printhead. Use unhydrated alcohol to wipe the needle out. If there is a missing needle position, it is mostly caused by a break of the needle. If there is no, it will cause other faults to prevent the needle from being released, such as the signal wire breaking, the burning of the printing needle coil or the blockage of the printing needle guide hole. After the needle is broken, you can replace it and continue to use it.
1. Several general-purpose needle replacement methods for printer head
(1) LQ-1900K/LQ-1600KⅢ/LQ-1600K4 print head
The LQ-1900K/LQ-1600KⅢ/LQ-1600K4 print head is a double-layer needle arrangement structure. The printing needles are divided into two specifications: long and short, each with 12 pieces. The length of the long needle is 36mm and the length of the short needle is 26mm. The 24 needles of this print head are arranged in odd and even. From the end of the guide plate in front of the print head, the column on the left is an odd number and the column on the right is an even number. Among them, the long needles are: 2, 6, 10, 14, 18, 22, 3, 7, 11, 15, 19, 23; the short needles are: 4, 8, 12, 16, 20, 24, 1, 5, 9, 13, 17, 21.
First, use the printhead needle breaking test program to check which pins have a fault, then cut off the printer power, remove the ribbon box, use a philtrum screwdriver to remove the two printhead fixing screws, pinch the heat sink of the printhead (i.e., the shell) from both sides, gently lift the printhead up and you can see the two flexible flat cables connected. Unplug the cable and take out the printhead. Use an alcohol cotton ball to scrub the ink stain on the front of the print head and check whether there is any needle deficiency.
If there is a broken needle, you need to change the needle. Tools should be prepared before changing the needle, mainly including tweezers, blades, diamond files, steel rulers, oil stones and special fixtures for printheads (a tool specially designed for disassembling the printhead heat sink). First use a crosshead screwdriver to remove the two screws that fix the print needle sleeve and the heat sink, and use a special tool to remove the heat sink. You can see that the printhead has several layers of structure, and then change the needles in the following order:
1) Put the head of the print head facing down, open the triangular claws that fix the upper and lower layers of the printing needles, remove the upper and lower back copper cover, and you can see the 12 long needles distributed around the ring. From the test results, distinguish whether the broken needle is a long needle or a short needle, then determine the position of the broken needle, use tweezers to remove the broken needle and put it aside; if there are short needles, take out all the long needles, and then use the blade to separate the yellow copper gasket in the middle to expose the 12 short needles, and use the same method to remove the broken needles. Then remove a good needle from the print head (the long needle or short needle depends on the broken needle), then use a steel ruler to accurately measure the length of the needle, grind the new needle with a diamond file according to the size of the quantity (note that the burrs on the needle are removed), and then insert it from the original position. After changing, gently press the tail of the 12 needles with your hand to make the needle protrude from the guide plate in front of the print head. At this time, you should see that the needles are exposed at the positions of the No. 1 needle and No. 24 needle, and a hole should be spaced between the needles in each row. If there is any wrong position, it must be adjusted. At the same time, when the fingers are released, each needle can be retracted immediately to ensure that the needle is released from each needle smoothly. Close the copper seat again, note that before closing the copper seat, the positioning pin of each needle must also fall into its groove.
2) After confirming that the short needles are all in place, press the upper coil seat (i.e., the long needle coil seat) together with the base (copper seat), and apply a set of +10V DC voltage to the driving coils of each group of printing needles respectively (the power-up time should be short, generally less than 1 second, which is equivalent to applying a pulse voltage on the coil), in order to test the flexibility of each printing needle and the consistency of the flight distance. To avoid reworking after installing the upper layer printing needle (long needle set).
3) Install the upper needle in the original order. Install the long needle layer positioning hole together with the coil seat. After checking that there are no gaps on the sides, you can install the long needle. The long needle only needs to be inserted according to the corresponding hole position. The long needle needs to pass through several guide grooves from the tail to the protruding head, and the uppermost slot is easy to insert. The second slot is a little harder. As long as you pass it through, the printing needle can go down along the way and it is easy to reach its position. Also press the tail of the 12 needles with your fingers. The needle should be poked 1mm from the guide plate in front of the print head, indicating that the needle you replaced is good. After inserting all, check that the positioning pins of each long needle must fall into its groove, and then close the rear copper cover. At this time, there should be no gaps when viewed from the side. Finally, install the triangular claws, put the heat sink, and use +10V power supply to check the long needle group according to the test method of the short needle group. After confirming that it is normal, it can be installed on the original printer for testing.
Before testing, do not install ribbons. Turn on the power and print a single sheet of paper to prevent the new needle from hanging ribbons. Then use the printhead needle breaking test program to test it, and it can be put into use after confirming that it is normal.
( 2) AR-3200/AR-3200Ⅱ/CR-3240Ⅱ Print head
The print head structures of the three needle printers are basically the same. Except for the elastic force of the print needle reset spring and the resistance of the printing needle driving coil of the three needles, the other ones are the same. The printing needles are all single-layer arrangement structures, and the length of the printing needle is 35.2mm.
The method of checking the needle breaking is the same as the above-mentioned EPSON LQ series printheads. Change the needle as follows:
1) Put the head of the printhead face down, remove the black plastic shell of the printhead, remove a movable I-shaped pad and then break open the two metal fixing clips with your hands, remove the rear cover, the printing needle armature press reed and the white plastic bracket in turn. At this time, you can see the armature of the 24 printing needles arranged in an endless row.
2) Use tweezers to remove the broken needle (when using tweezers to remove the broken needle, the action should be light. Do not bring out the nylon pin and return spring below the printing needle), and then remove a good printing needle from the print head, use a rigid ruler to accurately measure the length of the needle, grind the new needle to the size of the measured size, use a diamond file to remove the burrs on the needle head, then insert it from the original position, and use a finger to gently press the armature of the 24 needles to expose the needle from the guide plate in front, and observe whether all the 24 needles are out.
3) After replacing the white plastic bracket, the printing needle armature pressure spring, the back cover plate and the fixing card in sequence, install the print head shell, and apply a set of +10V DC voltage to the driving coils of each group of printing needle respectively (the method is the same as the LQ series print head), and test the flexibility of each printing needle and the consistency of the flight distance.
4) Put the printhead back on the original printer, do not install the ribbon first, print a single sheet of paper by self-checking (to prevent the newly installed printing needle from hanging up the ribbon), and then use the printhead needle breaking test program to test it. After the check is normal, it can be used.
2. Printing needle coil troubleshooting
Another common fault of the printhead is damage to the drive coil. The method to determine whether the driving coil is damaged is: insert one end of a printhead cable into the printhead, and use a multimeter to measure the DC resistance of the driving coil corresponding to the other end. Generally, the DC resistance of the driving coil should be 33 ohms±2 ohms. If the measured resistance value deviation is large, it may be that the coil is open or short-circuited, which will cause the needle to not be released or the needle is weak. During the test, you can connect one of the multimeter's pen to the common end and the other pen to the corresponding points of each driving coil. When replacing a single coil, you can first use a tin suction device to remove the solder on the coil and then use a blade to cut the surrounding glue, remove the single coil and replace it.
Most of the reasons for the open circuit failure of the print driver coil are damaged by the printing needle driver tube on the motherboard. The driving tube is broken down and short-circuited, which will cause the driving current to be too high and burn out the driving coil. To determine whether the drive tube is faulty, use a multimeter to measure the printhead cable: the red meter pen is connected to the common end (the common end is the positive electrode of the driving power supply), and the black meter pen is connected to the respective corresponding positions of the drive tube. In normal times, the measured DC resistance should be about 18 kiloohm. If the deviation is large, it means that the driving tube is damaged. Each drive tube corresponds to a root printing needle. For example, there are 24 drive tubes Q1~Q24 on the motherboard of the LQl600K printer, corresponding to the number 1-24 printing needles respectively.
Printers are a commonly used office equipment, which mainly include needle printers, inkjet printers, laser printers, etc. At the same time, printers are also an office equipment that is prone to failure, and repairing printers is ultimately the repair of damaged parts. Therefore, understanding and proficiency in the detection and repair of various parts of the printer will undoubtedly be of great significance to our repair work. The following is a guide to the testing and maintenance methods and techniques of common printer components. I hope it will be of some help to your printer repair work.
1. Maintenance of needle printhead
When a needle printer leaks a wire failure, it is mostly due to a needle breakage at the printhead. Use unhydrated alcohol to wipe the needle out. If there is a missing needle position, it is mostly caused by a break of the needle. If there is no, it will cause other faults to prevent the needle from being released, such as the signal wire breaking, the burning of the printing needle coil or the blockage of the printing needle guide hole. After the needle is broken, you can replace it and continue to use it.
1. Several general-purpose needle replacement methods for printer head
(1) LQ-1900K/LQ-1600KⅢ/LQ-1600K4 print head
The LQ-1900K/LQ-1600KⅢ/LQ-1600K4 print head is a double-layer needle arrangement structure. The printing needles are divided into two specifications: long and short, each with 12 pieces. The length of the long needle is 36mm and the length of the short needle is 26mm. The 24 needles of this print head are arranged in odd and even. From the end of the guide plate in front of the print head, the column on the left is an odd number and the column on the right is an even number. Among them, the long needles are: 2, 6, 10, 14, 18, 22, 3, 7, 11, 15, 19, 23; the short needles are: 4, 8, 12, 16, 20, 24, 1, 5, 9, 13, 17, 21.
First, use the printhead needle breaking test program to check which pins have a fault, then cut off the printer power, remove the ribbon box, use a philtrum screwdriver to remove the two printhead fixing screws, pinch the heat sink of the printhead (i.e., the shell) from both sides, gently lift the printhead up and you can see the two flexible flat cables connected. Unplug the cable and take out the printhead. Use an alcohol cotton ball to scrub the ink stain on the front of the print head and check whether there is any needle deficiency.
If there is a broken needle, you need to change the needle. Tools should be prepared before changing the needle, mainly including tweezers, blades, diamond files, steel rulers, oil stones and special fixtures for printheads (a tool specially designed for disassembling the printhead heat sink). First use a crosshead screwdriver to remove the two screws that fix the print needle sleeve and the heat sink, and use a special tool to remove the heat sink. You can see that the printhead has several layers of structure, and then change the needles in the following order:
1) Put the head of the print head facing down, open the triangular claws that fix the upper and lower layers of the printing needles, remove the upper and lower back copper cover, and you can see the 12 long needles distributed around the ring. From the test results, distinguish whether the broken needle is a long needle or a short needle, then determine the position of the broken needle, use tweezers to remove the broken needle and put it aside; if there are short needles, take out all the long needles, and then use the blade to separate the yellow copper gasket in the middle to expose the 12 short needles, and use the same method to remove the broken needles. Then remove a good needle from the print head (the long needle or short needle depends on the broken needle), then use a steel ruler to accurately measure the length of the needle, grind the new needle with a diamond file according to the size of the quantity (note that the burrs on the needle are removed), and then insert it from the original position. After changing, gently press the tail of the 12 needles with your hand to make the needle protrude from the guide plate in front of the print head. At this time, you should see that the needles are exposed at the positions of the No. 1 needle and No. 24 needle, and a hole should be spaced between the needles in each row. If there is any wrong position, it must be adjusted. At the same time, when the fingers are released, each needle can be retracted immediately to ensure that the needle is released from each needle smoothly. Close the copper seat again, note that before closing the copper seat, the positioning pin of each needle must also fall into its groove.
2) After confirming that the short needles are all in place, press the upper coil seat (i.e., the long needle coil seat) together with the base (copper seat), and apply a set of +10V DC voltage to the driving coils of each group of printing needles respectively (the power-up time should be short, generally less than 1 second, which is equivalent to applying a pulse voltage on the coil), in order to test the flexibility of each printing needle and the consistency of the flight distance. To avoid reworking after installing the upper layer printing needle (long needle set).
3) Install the upper needle in the original order. Install the long needle layer positioning hole together with the coil seat. After checking that there are no gaps on the sides, you can install the long needle. The long needle only needs to be inserted according to the corresponding hole position. The long needle needs to pass through several guide grooves from the tail to the protruding head, and the uppermost slot is easy to insert. The second slot is a little harder. As long as you pass it through, the printing needle can go down along the way and it is easy to reach its position. Also press the tail of the 12 needles with your fingers. The needle should be poked 1mm from the guide plate in front of the print head, indicating that the needle you replaced is good. After inserting all, check that the positioning pins of each long needle must fall into its groove, and then close the rear copper cover. At this time, there should be no gaps when viewed from the side. Finally, install the triangular claws, put the heat sink, and use +10V power supply to check the long needle group according to the test method of the short needle group. After confirming that it is normal, it can be installed on the original printer for testing.
Before testing, do not install ribbons. Turn on the power and print a single sheet of paper to prevent the new needle from hanging ribbons. Then use the printhead needle breaking test program to test it, and it can be put into use after confirming that it is normal.
( 2) AR-3200/AR-3200Ⅱ/CR-3240Ⅱ Print head
The print head structures of the three needle printers are basically the same. Except for the elastic force of the print needle reset spring and the resistance of the printing needle driving coil of the three needles, the other ones are the same. The printing needles are all single-layer arrangement structures, and the length of the printing needle is 35.2mm.
The method of checking the needle breaking is the same as the above-mentioned EPSON LQ series printheads. Change the needle as follows:
1) Put the head of the printhead face down, remove the black plastic shell of the printhead, remove a movable I-shaped pad and then break open the two metal fixing clips with your hands, remove the rear cover, the printing needle armature press reed and the white plastic bracket in turn. At this time, you can see the armature of the 24 printing needles arranged in an endless row.
2) Use tweezers to remove the broken needle (when using tweezers to remove the broken needle, the action should be light. Do not bring out the nylon pin and return spring below the printing needle), and then remove a good printing needle from the print head, use a rigid ruler to accurately measure the length of the needle, grind the new needle to the size of the measured size, use a diamond file to remove the burrs on the needle head, then insert it from the original position, and use a finger to gently press the armature of the 24 needles to expose the needle from the guide plate in front, and observe whether all the 24 needles are out.
3) After replacing the white plastic bracket, the printing needle armature pressure spring, the back cover plate and the fixing card in sequence, install the print head shell, and apply a set of +10V DC voltage to the driving coils of each group of printing needle respectively (the method is the same as the LQ series print head), and test the flexibility of each printing needle and the consistency of the flight distance.
4) Put the printhead back on the original printer, do not install the ribbon first, print a single sheet of paper by self-checking (to prevent the newly installed printing needle from hanging up the ribbon), and then use the printhead needle breaking test program to test it. After the check is normal, it can be used.
2. Printing needle coil troubleshooting
Another common fault of the printhead is damage to the drive coil. The method to determine whether the driving coil is damaged is: insert one end of a printhead cable into the printhead, and use a multimeter to measure the DC resistance of the driving coil corresponding to the other end. Generally, the DC resistance of the driving coil should be 33 ohms±2 ohms. If the measured resistance value deviation is large, it may be that the coil is open or short-circuited, which will cause the needle to not be released or the needle is weak. During the test, you can connect one of the multimeter's pen to the common end and the other pen to the corresponding points of each driving coil. When replacing a single coil, you can first use a tin suction device to remove the solder on the coil and then use a blade to cut the surrounding glue, remove the single coil and replace it.
Most of the reasons for the open circuit failure of the print driver coil are damaged by the printing needle driver tube on the motherboard. The driving tube is broken down and short-circuited, which will cause the driving current to be too high and burn out the driving coil. To determine whether the drive tube is faulty, use a multimeter to measure the printhead cable: the red meter pen is connected to the common end (the common end is the positive electrode of the driving power supply), and the black meter pen is connected to the respective corresponding positions of the drive tube. In normal times, the measured DC resistance should be about 18 kiloohm. If the deviation is large, it means that the driving tube is damaged. Each drive tube corresponds to a root printing needle. For example, there are 24 drive tubes Q1~Q24 on the motherboard of the LQl600K printer, corresponding to the number 1-24 printing needles respectively.