Service manual

108 Technical Overview Welch Allyn Propaq Encore Vital Signs Monitor
Expansion Module and Printer
The printer shares battery power with the monitor, but contains its own power supply. The
printer processor communicates with the monitor's processor through the expansion
connector and cable.
The Expansion Module is designed to house the Propaq Encore Printer and other circuit
boards for additional parameters. The main circuit board in the Printer is the Printer Main
Board. An additional circuit board (key panel) in the expansion module with printer front
chassis contains the push buttons.
The Printer Main Board is attached to the thermal printer mechanism and should be
replaced as a unit with the printer mechanism if repair is needed.
The Printer Main Board connects to the expansion connector, the battery pack, the push
buttons on the expansion module front panel, the printer mechanism (motor and print
head), and the paper out and head up sensors.
The printer’s microprocessor receives print data and control information from the Propaq
Encore and sends data to the Encore. Communication between the two systems (Encore
and printer CPUs) is done by sending and receiving data packets over serial
communication lines.
The print head assembly contains 5 segments consisting of 64 thermal printing dots each
for a total of 320 dots, which cover the width of the paper. As the paper moves under the
print head, the system enables each segment energizing the thermal dots as necessary.
The Printer Main board consists of five functional blocks: Printer CPU, Printer Driver,
Printer Logic, System Power, and Printer Power. These blocks are interconnected by
several control lines and buses. External to the Printer Main board are the key panel,
housed in the expansion module front chassis, and the printer motor and print head, both
parts of the printer mechanism.
The Printer CPU block receives data and control information from the Propaq Encore
through the Printer Logic block. The Printer CPU sends data to other printer circuits to
control printer functions and sense printer conditions.
Through the Printer Driver the CPU controls the stepper motor and detects when the
paper has run out.
The CPU loads print data into the Printer Logic block and, through this block, controls the
individual printhead segments. The CPU also interfaces with the Propaq Encore through
this circuitry.
The System Power block provides several dc power supplies to the printer.
The Printer Power block provides the +24V printer power supply.