A printer is a commonly used office equipment, which mainly includes a dot matrix printer, an inkjet printer, a laser printer and others. At the same time, the printer is also a faulty easily office equipment, and the maintenance of the printer is mostly the repair of its damaged parts, so understanding and proficient in the testing and maintenance of various parts of the printer will undoubtedly be of great significance to our maintenance work. The following is a procedure of the common repair and maintenance methods and techniques of printer parts. Hope that it will help you to diagnose and repair the printer.

Method / Step:

1. The maintenance of the print head cleaning and sealing device

The print head cleaning and sealing device is an important component of the print head, and in particular, the cleaning and sealing device for separating the print head is complicated. The entire device is mounted at the leftmost end of the printhead moving rail, ie, the protective position or initial position of the printhead. The device consists of a wiper, a wiper, and a shroud with aspirator. The device mainly performs four actions of “scraping, wiping, hooding, sucking”, thereby maintaining the print head to ensure its normal operation.

In the device, the structure of the “scraping and wiping” device is relatively simple, and it is not easy to cause malfunction, and at most, the rubber product is damaged, and can be removed and used, and the printing effect is not greatly affected.

The “hood” is the shield; its function is to seal the print head well when the printer is not in use, to ensure that the ink jet port has a certain degree of wetness, and to prevent the nozzle from being clogged. The common fault is that the airtightness is not tighten, and there are two main reasons for the fault: First, the shield is deformed. The shield has a certain elasticity, and the slight deformation does cause the sealing to be unsatisfactory. If the deformation is serious or the surface is contaminated with large impurities, the sealing is not tight; the second is that the shielding position is not in place. The shield has a range of motion in the radial and axial directions during operation to facilitate coordination with the movement of the printhead. When the movement of the shield is restricted, the printhead in the initial position cannot be accurately aligned. Both of the above faults can be observed directly, just adjust or replace the accessories will do.

“Suction” is the aspirator. Its function is to suck out the semi-dry ink in the print head and the gas in the ink supply system when the printer is turned on, the ink cartridge is replaced, or the print head is replaced, so that the print head is filled with fresh ink. To ensure normal printing. There are two common faults of the aspirator: one is that the ink suction tube is broken or peeled off; the other is that the ink suction port is blocked. Both will cause the negative pressure generated by the ink pump to not act on the printhead, making the printhead uncleanable. In the actual overhaul, it is found that the malfunction of the ink suction port is relatively common. Most of the faults are caused by the plugging of the sponge at the lower end of the ink suction port. After the fault is found, the sponge body can be replaced.

2. The ink tank maintenance

A common fault in ink tanks is the absence of ink or a slight handwriting. The reason is that the ink cartridges have a higher operating temperature, the ink is dry, or the operator injects different types of ink into the ink cartridge, and different types of inks have an interactive reaction. For ink tank failures, the ink tank must be cleaned and replaced with new ink.

In addition, the print head must be cleaned every time a new ink tank is installed. The new ink tank should not be placed in direct sunlight and dust. The storage temperature should be 10 °C-35 °C to avoid freezing and changing ink. The smaller the nozzle of the inkjet printer, the higher the resolution. At the same time, the smaller the nozzle, the higher the ink quality requirements. Therefore, the ink supplied by the manufacturer should be used as much as possible, and the inferior ink should not be selected.

3. The maintenance of the toner cartridge

The toner cartridge is the most important part of the laser printer and directly affects the quality of the print. Common faults in toner cartridges are scratches, fatigue and aging. The phenomenon of failure is that the image is dim, there are black lines, and so on. For fatigue failures, the toner cartridge can be placed for a period of time and the fault will automatically disappear. In addition, when the printing appears white lines parallel to the long side of the paper, most of the toner inside the toner cartridge is missing or the toner cartridge is damaged. Open the top cover of the laser printer, remove the toner cartridge and shake it to the left and right, and then put the toner cartridge into the machine. If the printing is normal, the toner in the toner cartridge is missing.

If the above failure occurs during printing, it is mostly due to fatigue or damage to the toner cartridge. In this case, you can use the following methods to repair: go to the chemical reagent store to buy some chrome trioxide, take 3-5 grams each time, use defatted cotton directly to smear some chromic oxide, along the drum axis Direction, gently, evenly and without any omissions. Be especially careful when wiping, to avoid scratching the tympanic membrane by nails and other hard objects. It is also not possible to use excessive force to prevent the photosensitive drum from being worn out and the photosensitive drum to be scrapped. In this way, the surface layer of the fatigued photosensitive drum can be removed to expose the photosensitive surface which has not yet been aged. Generally, the photosensitive drum which has been repaired can be re-exported one or two thousand sheets of paper or more, so that the life of the photosensitive drum can be continued. If the photosensitive film of the drum has fallen off, it cannot be repaired by this method, only the new drum is replaced.

4. High voltage generating circuit failure analysis and inspection methods

In a laser printer, there is a set of high voltage power supplies of about 6000V, which provides high voltage for initial charging and transfer discharge of the photosensitive drum assembly. The faults in the high-voltage circuit are mainly manifested in the following two aspects:

1. The high voltage generating circuit itself is faulty. The failure of the high voltage circuit itself is the damage of the oscillating circuit module (or integrated circuit), and the high voltage winding of the high voltage pulse transformer is open (the wire diameter of the high voltage winding is thin and easy to break). When encountering such a fault, the machine should be turned on to directly measure the DC resistance value of the high voltage winding of the high voltage pulse transformer with a multimeter to determine whether it is open.

2. Poor contact in the contacts. Poor contact contact means that the toner in the printer causes poor contact between the high-voltage output contact of the high-voltage generator and the developing bias contact point on the photosensitive drum assembly due to prolonged use; the photosensitive drum on the high-voltage generator circuit board Poor contact between the ground wire contact and the grounding point on the drum causes the printed page to be completely white or black. The method of checking this type of fault is to open the machine, take out the photoconductor kit, and check whether there are any dirt or toner on the relevant contacts in the printer, or the contacts on the photoconductor kit are free of dirt or toner.

5. The laser beam generator (laser head) is faulty.

Laser beam generator (laser head) failure refers to laser diode failure, mainly laser diode damage, coating lens aging on the focusing lens (to broaden the modulation band of the laser beam, must focus on the laser beam), resulting in printer printing A phenomenon in which the page is completely white or the resolution is degraded. The method of checking this fault is to open the machine, take out the laser, open the cover of the laser, and directly measure the DC resistance of the laser diode (with three pins) with a multimeter. Check that the coating on the surface of the focusing lens is aging, with or without dust or spots.

6. Fixing heater troubleshooting method

The secondary electrostatic latent image generated by the laser beam emitted onto the photosensitive drum is converted into a visible negatively charged toner image on the photosensitive drum by the magnetic roller in the photosensitive drum assembly, and then visible under the action of a high voltage positive charge The toner image is transferred to the printing paper, and finally pressurized by the fixing heater and simultaneously heats the printing paper to melt the toner on the printing paper, immersing it in the paper, and forming a permanent image on the paper. The fixing heater in a laser printer generally has two types of a lamp heater and a ceramic chip heater. The main performance of the fixing heater in the following three aspects:

1. The heater is damaged. Damage to the heater means that the heating lamp or the heated ceramic piece is damaged. When this phenomenon occurs, the image on the printed page will not be fixed firmly, and the toner will be dropped by the hand. In serious cases, the printer does not print, and there is a fault message (in the HP 4L, HP 5P/6P, HP 6L, HPll00, Lenovo LJ6P and other laser printers, the panel indicator light will be on, but in the HP 5000, HP 4VC, EPSON 5700, etc. Information such as FUSERERROR appears in the printer). The inspection method is to open the machine, take out the heater, and directly measure the DC resistance value of the heating lamp tube or the heating ceramic piece by the multimeter, and replace it if there is damage such as an open circuit.

2. The heater temperature sensor is damaged. In order to keep the fixing heater at a constant temperature during the print waiting phase (STAND BY), the initial rotation phase, and the printing rotation phase of the printer, the fixing heating assembly of the laser printer is equipped with a heater temperature detecting sensor, a control circuit thereof, and a safety protection circuit. (The thermal fuse) constitutes a fixing heating controller. For the heating ceramic sheet, the temperature detecting sensor is integrated on the ceramic sheet, and for the heating tube, the temperature detecting sensor is in close contact with the heating roller outside the heating tube. When the heater temperature detecting sensor is damaged, the fixing temperature is out of control, causing the fixing temperature to be too high or too low, and the printed page is over-fixed or too shallow (the printed image is easily erased). The inspection method is to open the machine and take out the heater. For the ceramic heating piece, use a multimeter to directly measure the DC resistance value of the temperature detecting sensor on the side of the hot ceramic piece; and for the heating lamp, the heating tube should be taken out. After removing the heating roller, measure the sensor resistance value under the heating roller. If it does not match the value, it should be replaced.

3. The fixing film is damaged. In order to prevent secondary transfer of the toner on the printing paper during the fixing heating process of the printer, the MFP is coated with a PTFE resin on the upper fixing roller of the laser printer (light tube heater) or directly outside the ceramic heating sheet. A Teflon membrane that can rotate freely on the heater is installed. For some reasons, such as improper handling of the paper jam, foreign matter enters the fixing roller, etc., causing partial damage of the fixing film, so that a certain area on the printed image is not fixed firmly or the printed image is regularly powdered. The inspection method is to open the machine, take out the heater, and check the fixing film for damage.

7. Overhaul of the pickup roller

The pickup roller of a laser printer is one of the wearing parts. When printing, when the paper in the paper tray is normal and the paper cannot be taken, the paper take-up roller is worn out or the spring is loose, the pressure is not enough, and the paper cannot be sent to the machine. When testing, the rubber band can be wound on the pickup roller. If the fault is removed, the pickup roller is worn. Otherwise, the pickup roller is normal, and the malfunction may be caused by improper installation of the paper tray and poor paper quality (too thin, too thick, damp).

8. The maintenance of the development roller failure

When the laser printer outputs blank paper, generally the developing roller does not absorb the toner. At this time, it can be measured whether the DC bias of the developing roller is normal; if it is not normal, the DC bias circuit should be checked. If the DC voltage is normal and the printer outputs blank paper, the developing roller is damaged or the drum is not grounded. When the negative charge of the photosensitive drum cannot be released to the ground, the laser beam cannot function on the photosensitive drum, and the printing paper cannot print the text. Check if the developing roller has gear damage and the developing part is in place.

9. Toner cartridge troubleshooting

When the prints have irregular toner marks, most of them are caused by powder leakage. The powder cartridge can be removed for inspection. The toner powder leakage fault is divided into two types: toner cartridge leakage powder and waste toner box leakage powder. Disassemble the visual inspection to find the specific part of the fault.

10. The rapid repair method of optical devices.

Common faults in optical devices are mainly optical lens shifts or dirt. When the optical lens is displaced, there will be no printing failure. Even if it can be printed, the printing will be incomplete. When the optical device is dirty, the printed image often has regular spots. Conversely, when the above phenomenon occurs in the printer, it indicates that the optical device is faulty. Clean the repair optics.

11. Rapid repair method of corona wire

The corona wire of the laser printer is equipped with a high voltage voltage, and the corona wire failure mainly manifests as a blank paper that cannot be played.

When such a fault occurs, it is important to check whether the corona wire is open or not, and whether the high voltage of the corona wire is low or 0V. For corona wire open circuit failure, the disassemble can be visually checked, and for high voltage abnormal failure, it can be determined by measuring whether the high voltage on the corona wire terminal is normal.


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