There are many articles about the introduction of LQ-1600K needle changing (such as “Computer News”, No. 14 and No. 42, 1998), and the needle changing steps are also more detailed, but the needle changing of the print head is relatively detailed. The description of bit arrangement and installation skills is not satisfactory, and these are the keys to the success or failure of repairing printers. The wrong installation method will lead to a wider range of broken needles, stuck needles, burned coils, and even the scrapping of the entire print head. Below, on these issues, combined with the author’s experience to make an explanation.
(1) Before maintenance, test work should be done to check the position of broken needle. It can usually be viewed visually, and can be viewed in a well-lit environment. Due to the relatively small needle-exiting surface, it is easy to see with the naked eye, which can be tested by patch24.com, the maintenance-free program for broken needles in UCDOS 6.0/7.0. The specific method is: in the UCDOS environment, type patch24/t to test. In this program, 24 needles are drawn out in sequence, and a total of 24 threads are printed. The needle without thread is the broken needle. The relationship between the needle size of the patch24 and the needle position of the print head is shown in Figure 1.
(2) The structure of the print head is relatively simple. It consists of a heat sink surrounding the core components of the print head. The core part is composed of the upper needle structure, the lower needle structure and the needle guide roller, which are fixed together by a fastening spring steel card. When repairing, the core components in the heat sink must be pushed out with force. Since the heat sink and the core components are fixed together with glue, when it is difficult to push out, you can use a wooden shim as a backing and hit lightly with a small hammer (note that Do not deform the back cover of the print head).
(3) The LQ1600K print head is divided into two layers, each layer has 12 needles. The lower layer is the short needle and the upper layer is the long needle. As shown in Figure 2, T1, T2…T12 are the arrangement positions of the upper printing needles (white dots); B1, B2…B12 are the arrangement positions of the lower printing needles (black dots). The long and short are alternately arranged, and all the upper needles need to be removed to replace the lower needles.
(4) The new printing needle must be polished before use. Because the new needle is often longer than the long needle, you should first look at the old needle and cut off the excess part. Be careful not to cut too much, and leave about 0.5 mm. Since the cut needle tip has burrs, it must be ground. When grinding, it can be ground with fine sandpaper (preferably with a fine sandstone or marble). It is necessary to ensure that the printing needle is ground vertically, and the needle should be continuously compared to prevent excessive grinding. Note that the printing needles cannot be longer or shorter. Be careful when cutting and grinding (the market reference price of printing needles is 10 yuan/piece).
(5) There are 12 needle-piercing holes in the upper layer. When installing the upper layer of needles, the needles need to be close to the guide grooves, and they can be pierced through the corresponding holes. When threading the needle, do not use too much force, nor do you need to thread it in place in one step. Just insert the needle into the hole, press the lower layer, gently shake the wrist back and forth, left and right, and let the printing needle rotate freely with the tail armature, and the printing needle will automatically Alignment, after alignment, it will slide in automatically with only its own weight. Be careful not to press and poke hard when threading the needle, as this will not only lead to misplacement, but also may break the needle and block the needle guide hole. The needle size and needle position of the upper layer are arranged as shown in the left picture of Figure 4.
(6) There are two inner and outer circles of pinholes in the lower layer, a total of 24 pinholes. The inner ring hole is for the upper needle; the outer ring hole is for the lower needle. When threading the lower layer needle, it also needs to be close to the guide groove and pierce through the corresponding outer ring hole. The needle threading method is the same as (5). It should be noted that, to replace the lower layer needles, all the upper layer needles must be removed. When piercing the needle, in order to prevent the wrong hole, it is best to pierce one hole and check the needle surface once. The needle size and needle position of the lower layer are arranged as shown in the right picture of Figure 4.
(7) After all the needles are threaded, fasten the fastening steel clips, and then check the needle surface, and grind the needle surface with a grindstone tip to ensure that all needle tips are in contact with the The needle face is exactly in one plane.
(8) Finally, put the print head into the printer, put the white paper into it, do not put the ribbon on it temporarily, and empty it for 20 to 30 minutes to make the needle further smooth. Make sure that the ribbon is not scratched.
Other precautions: 1 Because there are many small things inside the print head, be careful not to lose it when repairing. 2 The repaired print head is poor in heat dissipation and stability, so it is not necessary to change the needle if there are not many broken needles (less than 3) and the printing effect will not be affected. 3 When the repaired print head is printing documents, it is best to print on thick paper (the paper thickness adjustment lever is set to the 4 position or higher), which can reduce the printing speed to protect the printing needle. 4. When the repaired print head is printing documents, if it finds that the strokes are drifting, it means that the needle position is wrong and must be re-pierced. 5 When extracting or installing the print head cable, special care should be taken, and it should be pulled out or inserted slowly and evenly at the interface, and must not be pulled or inserted obliquely, otherwise the circuit chip embedded on the surface of the cable will Short circuit or poor contact.