Printhead Drive Circuit - OKIDATA ML380 Service Manual

Page: 18
Service Guide ML380
Chapter 2 Principles of Operation

2.1.05 Printhead Drive Circuit

This circuit is used to drive the 24 print wires. The signals HD1 through HD24 control the individual print
wires. The HD ON signal (even/odd trigger) enables the drive circuit when printing is desired. The head
drive duration is determined by an RC integrating circuit which modifies the HD ON pulsewidth. The
pulsewidth of the HD ON signal varies with the number of pins being driven. The drive time increases as
more pins are driven, and decreases as fewer pins are driven. The RC circuit compensates for the
fluctuation of drive voltage (+35 vdc).
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