OKIDATA ML393C Plus, Руководство по обслуживанию

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Service Guide ML393/ML393CPlus
Chapter 2 Principles of Operation
2.2 MECHANICAL OPERATION
2.2.01 Printhead Mechanism
The printer uses a highly efficient stored energy type printhead. Power is not consumed until the printwires
are activated. This extends printhead life to approximately 200 million characters.
The printhead uses 24 printwires (two columns of 12 wires each). Each wire is welded to an armature.
Behind this armature is a spacer ring.
Each of the 24 printwire armatures have a permanent magnet behind them. The magnets attract the
armatures, drawing the printwires into the wire guide. This keeps the wires inside the printhead. A coil is
wrapped around each of the permanent magnets.
When a dot is to be printed, current passes through the appropriate coil. This creates an electromagnetic
field which opposes the magnetic field of the permanent magnet. The armature springs forward. The print
wire (which is attached to the armature) strikes the ribbon and prints a dot on the paper.
When current is removed from the coil, the magnetic field of the permanent magnet attracts the armature,
retracting the printwire into the wire guide.
The printhead contains a built-in thermistor used to monitor the printhead temperature.
The parts listed below make up the printhead.
Wire Guide
Print Wires
Armature Assembly
Spacer
Permanent Magnet Assembly
Thermistor
Printed Circuit Board with Coils
Head Gap Adjusting
The head gap adjusting mechanism adjusts the gap between the platen and printhead.
Move the adjusting lever on the left side of the printer mechanism to change the head gap.
When the lever is moved, the carriage shaft rotates. The carriage shaft is attached to the printer
mechanism with eccentric collars. As the carriage shaft rotates, the distance between the platen and
carriage shaft changes.
Two items factor into printhead gap information.
1. Printhead Gap Adjustment
This is a SERVICE ADJUSTMENT made by a technician.
It is covered in Section 3.3 of this Service Handbook.
The Adjustment measures 0.017, +/- 0.001 inches (0.43, +/- 0.03 mm).