Main sections of a Dot-Matrix Printers are:
-Mechanical Section of Printer
-Electronic Section of Printer
Mechanical Section
While Printing the moving parts of the Printers are called as Mechanical Section. The main parts of the Mechanical section are:
-Carriage motor
-Paper feed motor
-Gears
-Head
-Belt Roller
-Home and Paper sensor
-Ribbon
-Ribbon Cartridge
-Cartridge Assembly
Electronic Section
This section is divided into three parts:
-Power supply section
-CPU section (Logic Board)
-Interface Section
Printers by different companies have different IC’s used in these sections. Some Printers have all these sections on separate PCB board and some printers have two sections on a single board and third section on a separate board.
Printing Process
When Printers are switched on, different regulated DC voltages from power supply sections are supplied to the logic sections.
The CPU reads the information from DIP-switch setting and then supplies signal to the gate/array IC.
This is called Printer Initialization. When Printer head moves to the column one position, home sensor senses the printer head and supplies the signal to the gate/ array IC to stop further movement of its head. Now if the paper is in the Printer comes in ready and online position. When the print command or job from Computer is supplied to the printer is supplied to the gate/array IC, RAM and CPU through the buffer IC.
The computer supplies the data, control signals and selected font information to the printers. The Printer’s CPU supplies to gate/array IC according to the selected font.
The main function of gate/array IC is to control stepper motor, carriage motor and print head.
The gate/array IC supplies signal for first character to the printer’s head for printing at column one.
After printing first character the gate/array IC supplies signal to the line driver/stepper driver to move the paper up by one line.
Next, gate/array IC supplies signal to the carriage controller to move the head to the left at home position.
Now again the above process is repeated to print the next line.
When the paper ends, the paper end sensor supplies to signal to gate/array IC. The gate/array IC supplies this signal to the computer to stop supplying the data.
When the paper is placed into the printer, the previous data stored in the Printer’s RAM is printed first, then the newdata from Computer is printed.
Different Parts of the Dot-Matrix Printers
The main parts of the Dot-Matrix Printers are:
1. Front panel/Controlpanel
2. Microprocessor
3. Peripheral Controller/Gate Array IC
4. RAM
5. ROM
6. Carriage driver/controller
7. Stepper driver/controller
8. Pin/Needle driver
9. Buffer IC
10. Fonts
11. DIP Switches or Jumper
Printers Troubleshooting
If there is a fault in the printer then user has to first check whether the fault is in:
1. Computer Section
2. Computer Interface Section
3. Printer Section
If there is no printing of data receive from the Computer then check the following:
1. Computer Section
First check the port of the Computer into which printer is connected. Check the address of the port and check the signal output from the board.
2. Computer Interface Section A parallel interface cable is used to connect the the printer with parallel port of the computer. This cable has 25-pin male type connector on one side and 36-pin edge type connector is connected to printer interface.
3. Printer Section
The printer can be testing by following two ways:
a) Self Test
Each printer has a self test facility. The self-test is taken after disconnecting the printers from Computer. While printing the self-test page all parts of the Printer is operated except buffer. If the the self-test page printing is OK then it means Printer is OK.
b) Test Page by Computer
While printing test page from Computer all parts of the Printers are dead then check the printers are dead then check the Printer Circuit.
