Analysis of dot matrix printer car faults

Under normal circumstances, the left and right displacement of the car in the dot matrix printer should be smooth and stable, so that after the printer is started on, no matter where the car is located, it can return to the initial position on the left end, when the printer is working, the car holds the print head to move back and forth. If a car fails, the print head will not be moved to the position or not at all, leading to the failure of printing. The following is a detailed discussion of the word car fault, the word car fault mainly manifested in the following aspects.
1. There is too much dirt in the car structure, which often causes the car to fail to return to its position smoothly. In this case, the cleaning method can be used to eliminate the fault.
2. Mechanical Faults of the word car mechanism, such as wear of the belt of the word car, parallel displacement of the front and rear rails, etc., will also make the word Car Unable to return to position and move smoothly. In this case, you can only change the car belt or guide rail.
3. Word car motor fault
The fault of byte motor itself is mainly caused by the burning of a group of stepping motor or multi-phase winding coils (short circuit and open circuit). This fault can be directly measured by A multimeter with the DC resistance of the motor coil winding and the normal resistance (in general, the four sets of coils of the motor will not all burn out, and there will always be one or more sets of coils that are good) for comparison and judgment. If the one-phase or two-phase burned out of the motor coil, as long as the coil skeleton is not deformed (the rotating shaft is rotated by hand, no graphics card is needed ), at this time, you can burn the motor according to the original wire diameter and turns (when removing the burned coil, pay attention to the number of turns, and then use the shard card to measure the wire diameter; if the coil skeleton of the motor has been seriously deformed, replace the new motor. In addition, in the long-term use of the printer, due to vibration and other reasons, may cause the magnetic steel part of the motor to be demagnetized, resulting in the motor rotation torque is insufficient, leading to the printer in the printing process word car movement is difficult. In this case, replace the new motor of the same model.
4. switching circuit faults
For the use of "high pressure drive low pressure lock" word car Motor Drive System printer, such as AR-3240, AR-2463, AR-3200, LQ-1500, LQ-800/1000 and other printers, high/low voltage Switching circuits often provide high-voltage transistor c ~ When the e pole breaks through or opens the circuit. If c ~ When the e pole breaks through, the driving high voltage is always added to the winding of the stepping motor, which may further cause the motor winding to burn out and burn out the transistor used to drive the phase signal of the stepping motor. If c ~ E pole open circuit, high voltage cannot supply the word car motor, the motor is not running, the word car will not move.
In addition, some control signals for high/low voltage switching may also fail. In this case, the circuit of the specific printer model should be checked and excluded.
5. Phase Failure of Motor
After the printer is powered on, if there is a group or two groups of open circuits on the four-phase winding of the stepper motor, the car will shake or the car will be weak at the original position, even the word car does not move. This phenomenon may be caused by poor contact or disconnection between the plug of the motor, or the phase control part of the motor control and drive circuit of the car. Because the circuits of various printers are different, we need to analyze and test the specific circuits to 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 transistor or dedicated Integrated Circuit Used by some printers to control and drive the motor. Such as AR-3240 printer and M-2724 printer in the word car stepper motor respectively using transistor D1579 and D1789 as their respective words car motor driver, while in the DLQ-2000K, AR-4400 and CR-3240 printer with SLA7026M as the word car motor driver, if these devices are damaged, the word car can not work normally. Only damaged components can be replaced.
7. Gate Array circuit faults of the Motor Drive Circuit
By the CPU through a dedicated gate circuit (such as E05A09BA in a LQ-1600K printer) or I/O interface circuit (such as E05A24GA IN A DLQ-2000K printer and AR-3200 IN A XBL-2 printer) the motor driving circuit of the car is controlled. If this part of the circuit is damaged, it will affect the normal operation of the car, and even when the printer is powered on, the car does not return the initial position.
Although the word car fault can be attributed to the above five parts, from the perspective of maintenance, it should be analyzed and diagnosed according to the various fault phenomena of the printer. The inspection sequence is generally: printer car mechanism (mechanical fault) --- car motor (resistance and torque of each phase coil) --- The resistance value of the output socket driven by the car motor (positive and reverse resistance) --- the power supply voltage of the motor drive --- the ground resistance of the input and output ends of the driving circuit --- the Phase Control Circuit of the motor.
The following is an example of Fault Analysis and troubleshooting:
1, CR-3240 printer boot after the word car operation is not normal
Fault Phenomenon: After the CR-3240 printer boot word car can return to the initial position, and the printing process of the word car to the right when the printer "dead ".
Diagnosis and Elimination: when a car returns to the initial position, the control logic of the printer is normal, and the control signal of the motor is normal, mainly because the torque of the motor is insufficient. The reason for the insufficient torque of the motor of the car is not only due to the lack of phase operation of the motor, there are two reasons: first, the low voltage of the drive power supply, second, the iron-steel part of the motor is demagnetized due to its long-term use of the motor due to vibration. If the fault possibility of SLA7026M motor drive circuit and its peripheral circuit is ruled out, replace the motor with a replacement method to resolve the fault.
2, AR-3200 printer boot after the word car operation is not normal
Fault Phenomenon: AR-3200 printer after the boot of the word car on the original location jitter, with a hand push word car moving a distance after the stop alarm.
Diagnosis and troubleshooting: From the fault phenomenon analysis, it refers to the word car fatigue, generally the printer's word car mechanism and the word car motor control and driving circuit fault. In the inspection order, first check the word car organization and eliminate this part of the fault. Then measure the resistance of each phase coil of the motor. Each phase is 5 Ω, which is a normal value. Then use the replacement method to check the torque of the car motor (the torque of the car motor of the AR-3200 printer will decrease after a period of time), the torque does not change, thus eliminating the possibility of failure of the car motor. Measure the drive output of the motor of the car on the main control circuit board to remove the positive and reverse resistance of each foot of CN5, and measure the short circuit between 2nd feet and the ground. Follow this end to check and find the phase signal output end (9 feet) of the SLA4030 (TA7) motor driving circuit to short the ground. Then, it is determined that SLA4030 is damaged. After SAL4030 is replaced, troubleshooting.
3, LQ-1900K printer after the boot of the word car jitter, with a hand push word car can move.
Diagnosis and Analysis: There are two reasons: one is the mechanical fault of the printer, and the other is the fault of the motor and its control and driving circuit, in addition, a phase of the motor is not working properly. For the mechanical failure of the printer, the left and right displacement of the car should be smooth and stable under normal circumstances, so that after the printer is powered on, no matter where the car was originally parked, it can return to the initial position. If there is too much dirt in the structure of the car, or the Bushing of the frame is seriously worn, shake the frame on its axis, this will cause the text car to fail to return to the initial position smoothly due to excessive resistance during the moving process, or the return to the initial position is not in place. The solution is to remove the structure of the car for cleaning, and replace the bushing for the frame with serious wear. After the above check, the motor drive circuit fault of the car is preliminarily diagnosed. Static Measurement of the DC resistance of each phase coil of the motor. The measured resistance is about 5 Ω, which indicates that the motor is normal. Use an oscilloscope to observe the output waveform of each input (,) of the SLA7024M drive circuit of the car motor. Static Measurement of the positive and reverse resistance of the 8-pin to the ground. The measured positive and reverse resistance values are 1kb. The normal positive resistance value should be ∞, and the reverse resistance value should be 7.5kb, this indicates that SLA7024M's 8 feet are damaged. After replacement, the fault is rectified.