Control Heater Dac, Driver Circuitry, And Valve Driver Circuitry; Power System Status Circuitry, Diagnostic Leds, And Switches - Bayer HealthCare RapidPoint 400 Series Service Manual

Control Heater DAC, Driver Circuitry, and Valve Driver Circuitry

This section Main board contains IC U25, which is an AD7247 dual DAC.
This IC takes digital data from the 68332 and creates two analog voltages
with a resolution of 12 bits. These heater voltages are sent to operational
amplifier U54, which multiplies the voltage by four and drives power
transistors Q4 and Q3.
Section A of DAC IC is for the block heater and section B is for the
preheater. These signals leave the Main board on connector J7 and are
sent to the heater resistance pads on the measurement block assembly.
Thermistor R229 is mounted near the power transistor heatsinks and
monitors for failures such as air flow restrictions). When R229 detects a
failure, it notifies the DAS section.
This section Main board also contains IC U28, which takes digital latched
signals from RTP CPLD U38 and forms the proper sequencing signals to
drive the luer position motor located in the equipment wall module. These
driver signals exit the Main board through J3.

Power System Status Circuitry, Diagnostic LEDs, and Switches

This section Main board contains the MC34161 power supply monitors:
ICs U39, U40, and U43. These ICs are voltage window comparators, which
verify if the ±12 and +24 V power supplies are within the rated tolerance.
The 68332 reads signals ±12 V_STS and +24 V_STS from the RTP data
bus through transparent latch U12.
This section Main board also contains IC U44, which is a dual comparator
that checks the motor power supply. U44 ensures that motors are
operational by measuring the voltage drop across resistors R188. The
68332 reads signals MOTOR_STS from the RTP data bus through
transparent latch U38.
This section Main board has eight diagnostic light-emitting diodes (LEDs),
CR2 to CR9, that are latched by U59 onto the RTP data bus. There is also
an eight position dip switch, SW1, which is read by the RTP data bus
through transparent latch U50.
Rev. C Electronic System Overview 89