Fault Phenomenon 1: After adding paper, the abparation lamp is still on, no print analysis and exclude: the printer has three sensors, and the two reed sensors are used to detect if there is no paper feed. Once the paper touches the sensor's reed, make the touch of the sensor, the printer will activate the feed program, automatically send paper to the exact location, and prepare for printing. During this process, whether the printing paper reaches the corresponding position, and another photoelectric sensor is responsible for detection. When the paper is in place, the abparation lamp on the control panel is extinguished.
From the above fault phenomena, it is estimated that the photoelectric sensor has faults. The author draws a partial circuit between the photoelectric sensor and the main control circuit board according to the actual object, as shown in the figure. From the figure, the light-emitting diode is connected between 1 pin and 3 foots of the plug-in CN5, and the resistor R6 is connected to the supply circuit of 5V to the light-emitting diode, which acts as a step-down and current limitation. Under normal circumstances, when there is no paper, the photosensitive tube is not reflected from the printing paper, and the 4 pin outputs low; when there is paper, the photosensitive tube is turned on, and the 4 pin output is close to 5V high electricity. level.
In the online state, measurement of 4 foot voltages with a multimeter, regardless of paper or paperless, 4 foot voltages are low; and when the light is irradiated, the 4 foot voltage changes high, indicating that the photosensitive tube is good. Then, a pin voltage is 5V, not normal (normally, the voltage across the light-emitting diode is reduced to around 2V). Check the connection between the probe and the soft cable, the connection is good. Therefore, it is judged that the luminous tube has opened. Replace the new photoelectric detection probe, troubleshooting.
Fault phenomenon: suddenly stopped when the printer is used, turn it off after shutting down, no reaction, the power light is not bright.
Analysis and exclude: Open the printer casing, unplug all connectors, remove the printer housing and shield, and expose the circuit board. Check the power supply circuit and find that the fuse is intact, and the other portions have not found significant burnt marks. Booting multimeter detects the rectified output, there is a 300V voltage output, normal. Since the circuit structure and the definition of the other parts of the power supply circuit are not cleared, it is not possible for a while.
With years of experience accumulated in many years, they decided to check from the load. First, check the plug connected to the main control board to clear the functionality of each plug. Wherein CN6, CN7 is a driving signal line of a long needle and a short needle of the printhead, and CN8 is a paper-drive motor drive signal line, and CN9 is a vehicle motor drive signal line, and other plugs are sensor connections.
Next, the method of extracting the test machine by pulling the load is used, and the four plugs of CN6 ~ CN9 are tested, and the printer power indicator is not lit. Considering that the light emitting diode in the photoelectric sensor is also a power supply load, it is determined that the CN5 and the CN12 of the connection checking sensor are then removed, respectively, and the CN12 of the initial position sensor is tried. Sure enough, when the CN5 is removed, the printer power light is on, and the cart in the boot also has a corresponding self-test action.
The CN5 soft cable is measured with a multimeter, and it is found that its 2 feet and 3 feet are short. When the CN5 is inserted into the main control board, the 5V is directly grounded, thus causing overcurrent protection of the power supply circuit. When further examination, it was found that the soft cable and the probe connection have been distorted. Use a scissors to cut the section of the tip of the cable, then scrape it out with a blade, reconnect the test machine, troubleshoot.
Fault phenomenon 3: During printing, take a row when I went on, and a group of Chinese characters are divided into two.
Analysis and Excluding: Self-testing operation of the printer, normal, indicating that the printer itself controls the logic and mechanical transmission portions can work normally, and the fault may only be in the host, printer interface circuit or signal cable portion. According to the prior need of maintenance principles, first check the connection of the signal cable, it is found that the screws at the signal cable and the host connection are not tightened, the joint is inclined. After pulling the joint, re-inhaul, and tighten the two-headed fastening screws, boot test, troubleshooting with a word-shaped screwdriver.
