3/6/08 888-2463-001 4-11
WARNING: Disconnect primary power prior to servicing.
Section 4 Theory of Operation
Diamond Series™
4.6 Control Cabinet Detailed Circuit Description
4.6.1 Main Controller
The Main Controller consists of programming in a 32-bit micro processor chip. The
control functions are divided into six parallel processes. Some of these processes also
have sub-processes under them.
• Communications Process
• Input Signal Process
• Control Process
• Fault Process
• Interrupt and Timer
• System Maintenance
4.6.2 Life Support
The Life Support board allows transmitter operation when there has been a loss of the
Main Controller board. The transmitter will operate at full power but with limited
system level protection. The Cabinet Controllers still maintain full protection of the
cabinet level components.
4.6.2.1 AC Fail
Upon AC failure, each PA Cabinet Controller in the PA Cabinets will send an active
LOW signal to its corresponding pin on J1 pins 12-14 and 16-17 of the Life Support
Board. Any failure of a single phase AC input to the PA Cabinet will cause the
AC_FAIL at this input, illuminate DS13 on the Life Support board and will report to the
complex programmable logic device (CPLD) U10.
The AC Fail detector receives a DC voltage proportional to the AC line voltage from
the Low Voltage Power Supply at J1-18. This voltage goes to two comparator circuits at
U44. The AC Fail circuit will turn the transmitter OFF by sending an OFF command to
the Main Controller in addition to reporting to the CPLD, which sends a command
through the parallel bus to the rest of the system. The Low Voltage Power Supply will
also send an AC_OK_L signal at J1-19 which will do the same as the detector circuit as
a back-up to turn the transmitter OFF.
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