Sensor Calibration; Joint Board; Psu And Voltage Indicator - Digital Equipment LB12 Field Support Manual

Sensor calibration

2.1.12

Joint board

2.1.13

PSU and voltage indicator

9710
The threshold values are calibrated for each opto-sensor at each power-ON to compensate
for component degradation and variations in component characteristics. A calibration
reference is made by running a special calibration function (see Chapter 3, Maintenance ).
During calibration, all sensors are set to their WHITE or OPEN state. The sensor outputs
are then transferred, one at a time, to the comparator. For each sensor, the CPU changes
the threshold voltage until the SENSE signal changes to HIGH level. That threshold voltage
is then multiplied with a factor to obtain the calibrated threshold voltage to be used.
The joint board connects the carriage motor to the main board. The joint board contains
only connectors.
Voltage conversion is achieved in two steps on the PSU board. The first step is an AC/DC
conversion, which generates +36 V used for the motors and the needle drive circuits on the
printhead board.
The second step is a DC/DC conversion from +36 V to +5 V and –12 V. A +12 V voltage is
generated on the main board by a voltage regulator supplied from the +36 V. Only the +5 V
is provided with a LED indicator (ON lamp) located at the front of the printer.
LB12/LB15 Field Support Manual
(See Figure 2-27)
2-23