IOMM AGR AGR 055A through 100A 89
Trouble Analysis for the AGR MicroTech Controller
Microprocessor Control Board
The Microprocessor Control Board (MCB) is shown in Figure 36. It contains a microprocessor that
is preprogrammed with the software required to monitor and control the chiller. The various MCB
connections and components are described below.
Figure 36, Microprocessor Control Board (MCB)
RUNNING
RESET
ACTIVE OUTPUT 0
CPU
STATUS
POWER FUSES
[BUSSMAN GDC-T2A]
POWER IN
[18-24 VCT]
AC AC GND GND
AUX/OUT
DIGITAL OUTPUTS
ANALOG INPUTS DIGITAL INPUTS
HI
ADDRESS
LO
KEYPAD/LCD DISPLAY
COMMUNICATIONS
PORT A PORT B
[FUSE: BUSSMAN MCR-1/4]
FUSE 1
2
3
4
Hex switches
Microprocessor status LED's
EXPANSION BUS
Digital Inputs Connection
The MCB receives digital inputs from the Analog Digital Input (ADI) board through the Digital
Inputs connector via a plug-in ribbon cable. These inputs are conditioned by the ADI board.
Analog Inputs Connection
The MCB receives conditioned analog inputs from the ADI board through the Analog Inputs
connector via a plug-in ribbon cable. These inputs are conditioned by the ADI board. After having
been conditioned, all analog inputs enter the MCB through the Analog Inputs port as 0–5 Vdc
signals.
Digital Outputs Connection
After processing all input conditions, the MCB sends the appropriate output signals to output
devices through the Digital Outputs port via a plug-in ribbon cable.
Power In Connector
The MCB receives 18 Vac, center-tapped power from transformer T4 through the Power In
connector. This power drives all logic and communications circuitry.
Power Fuses
Two identical 2-amp fuses are located to the right of the Power In connector. These fuses are in the
MCB power supply circuit.
Microprocessor Status LEDs
The green, red, and amber LEDs on the MCB provide information about the operating status of the
microprocessor. The amber LED also indicates the existence of alarm conditions.
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