Printhead Drive Circuit - OKIDATA ML395C Service Manual

Page: 18
Service Guide ML395/395C
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 pulse width.
The pulse width of the HD ON signal varies with the number of pins being driven.
Printhead Drive Time
The drive time increases as more pins are driven.
The drive time decreases as less pins are driven.
The drive time also increases if the head gap lever is placed in positions 4 through 9.
An RC circuit also is used to compensate for the fluctuation of drive voltage (+38 vdc).2-1-04B.pcx
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