Printer power board maintenance
The thermal protector in the power transformer fusesAs mentioned earlier, the power transformer buck type power circuit has a heat protector in the primary winding of the power transformer, and if it fuses, it will cause the transformer primary winding to open and can not supply power. After the short circuit fault of the input and output terminals of the power transformer is excluded, the following methods can be used for restoration.
The printer adopts low voltage power supply mode, mainly has two kinds of logic power supply and drive power supply. Logic power supply is usually DC +5V, providing power for various control chips. If it is a serial port printer, the logic power also includes a DC +12V to provide a working voltage for the serial chip. Drive power supply is usually DC +35V (some models are 36V or 24V), mainly for word car, motor, paper fed motor, printed needle driver to provide working power.
There are many ways to examine and repair the power circuit. It can not be generalized. The following common methods are introduced. Printer power system typical faults are: after power up, the panel indicator light is not bright, the whole machine does not respond; a certain set of abnormal voltage output and power transformer damage. Here, on the basis of an analysis of the causes of these failures, the details are presented
The rear panel power indicator light does not shine, the non response under normal circumstances to the printer power and boot, power operation panel indicator light should be lit, the car returned to the left word initial position, and then began to print the normal operation of the. The power indicator light is supplied by an internal +5V DC power supply, and the +5V power supply is also used for all logic circuits, as well as for "high voltage drive, low voltage lock" motors. If there is no +5V power or +5V power abnormal, the operation panel will not turn on the lights, the logic circuit does not work, the inevitable occurrence of words can not return to the left of the car, the printer does not respond to any fault. The common causes of such failures are the following.
+5V loop DC fuse fuseSome of the switching regulator circuit without power transformer, the +5V voltage regulator circuit input or output is also provided with a DC fuse, if the insurance tube fuse, can also cause such failures, usually due to short-circuit point of logic circuit.