Principles of Operation
Service Manual 6-5
Speaker
The unit’s speaker is located inside the front enclosure (see Figure 10-27 on
page 10-37). The speaker generates alert tones (such as when POST passes),
alarm tones, and key clicks. It is connected to and driven by the power PCBA.
There is no external speaker opening.
UI PCBA
The UI PCBA is located inside the front enclosure below the operator’s panel
(see Figure 10-10 on page 10-12). It contains the UI microprocessor which is
responsible for all user interface functions. The UI microprocessor displays
information and menus on the LCD and receives user input from the keypad.
It sends commands based on the input to the A/D microprocessor on the
power PCBA which controls the unit’s power, fan, and heating functions.
The UI PCBA also contains a real-time clock (RTC) that allows filter use to be
tracked and log/code entries to be time-stamped. The replaceable battery for
the RTC is located on the UI PCBA.
The USB connector on the UI PCBA supports software updates, error log
downloads, and other service functions performed at Covidien Service
Centers.
Power PCBA
The power PCBA is located inside the front enclosure (see Figure 10-24 on
page 10-31). It contains the A/D microprocessor and control circuitry for the
fan, heater, and thermostat.
The power PCBA has power input connections from the AC power inlet and
power supply, and output connections to the heater, fan, thermostat, and
speaker. The power PCBA converts the 48VDC output from the power supply
to various voltages required to power components throughout the system. The
power circuits are protected by redundant fuses located on the PCBA.
The A/D microprocessor maintains a communication channel with the UI
microprocessor and controls power to the UI PCBA and display. It also receives
input from the thermistor and relays that input to the UI microprocessor which
displays the temperature readings on the LCD.
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