Oki MICROLINE 390 Maintenance Manual

Also see for Microline 390: Handbook Product update Service manual User guide Product update

3.2 Mechanical Operation3.2.1 The printhead mechanism and its operation (See Figure 3.3.)The printhead is a spring charged type 24-pin driving head utilizing a permanent magnet. It isattached to the carriage and moves parallel with the platen.(1)(2)Figure 3-2 Arrangement of the head pins(View from the tip of the printhead)The printhead is composed of the following parts:(a) Wire guide(b) Print wires(c) Armature assembly(d) Yoke(e) S p r i n g(f) S p a c e r(g) Magnet assembly(h) Thermistor(i) Printed circuit boardOperation of printheadWhen the printhead is inactive, the armature is attracted to a permanent magnet and thespring attached to the armature is compressed. The print wires attached to each armature arethus concealed inside the wire guide.When a signal for a character to be printed is detected, current flows through the coil. Themagnetic fluxes (caused by the permanent magnet which is situated between the armatureand the poles) are canceled, removing the attracting force. The armature is driven in thedirection of the platen by the force of the armature spring expanding. The print wire attachedto the armature protrudes from the tip of the wire guide, striking the ribbon and prints a doton the paper.After the character has been printed, the armature is attracted to the permanent magnetagain and the print wires are concealed inside the wire guide.3-12