Epson LQ-1170 Service Manual page 87

4.2 BIDIRECTIONAL PRINT POSITION ADJUSTMENT
This section describes how to adjust the bidirectional print position to ensure correct printing alignment.
4.2.1 Overview of Bidirectional Print Position Adjustment
This printer prints characters when the carriage is moving in either direction (i.e., from left to right or
from right to left). Adjustment is necessary to ensure that the printing of characters in one direction
is properly aligned with the printing of characters in the opposite direction. For example, if the the print
position is out of alignment, printing of a vertical line shows staggering because of the skew effect.
It is important to readjust the bidirectional print position if anything has been done to the gear
arrangement that might affect this printing alignment. By making the timing lag slightly during printing
while the carriage moves from right to the left, it is possible to line up printing done in this direction
so that it will match printing done in the left-to-right direction. The procedure to alter the timing is called
the bidirectional print position adjustment.
The degree of bidirectional prin~ng skew differs, depending on the unique characteristics of each
printer mechanism. For this reason, there is no standard skew correction value that can be applied to
each printer. The unique skew correction value for each printer has to be written to EEPROM on the
main board.
Whenever the printer mechanism, or the main board itself, is changed during servicing, the bidirectional
print position must be readjusted and a new bidirectional skew correction value must be written to
4.2.2 Bidirectional Print Position Adjustment Procedure
Initial operation
Before performing the bidirectional alignment adjustment, complete the initial operation below:
Position the adjustment lever at position O.
Verify that the DIP switch setting for high-speed draft is off (DIP switch 1-6 is on).
Verify that the DIP switch setting for country is U.S. (DIP switches 1-1, 1-2, and 1-3 are on, and 1-4
is off).
Load paper.
Feed at least 10 lines.
Turn the printer off.
NOTE: The printer enters unidirectional printing mode automatically from the top of form to the line
10 position on the paper, because
perform the bidirectional alignment
Adjustment operation
The alignment procedure is as follows:
1. Turn the printer power on while pressing the ALT, LF/FF, and LOAD\ EJECT buttons.
2. The printer enters draft mode and prints the reference value and "1" characters for 4
.
this improves paper-feed accuracy. Therefore, you must
adjustment after 10 lines or more have been fed.
4 - 4
lines.