OPTIMOD-AM DIGITAL TECHNICAL DATA
6-11
normally. Please note any such messages and be ready to report them to Orban Cus-
tomer Service.
The DSP chips are located on the DSP board — see the drawings starting on page 6-
52. U701 and U702 are local voltage regulators on the DSP board that derive the
+3.3V supply for the DSP chips from the system digital 5V bus.
Power Supply
Warning! Hazardous voltages are present in the power supply when it is connected
to the AC line.
The power supply converts an AC line voltage input to various power sources used
by the 9400. To ensure lowest possible noise, four linear regulators provide 15VDC
and 5VDC for the analog circuits. A switching regulator provides high current
+5VDC for the digital circuits. An unregulated voltage powers the fan and feeds lo-
cal regulators.
The power supply circuits are straightforward and no explanation is required be-
yond the schematic itself. Be aware that C1, C4, C5, and C12 in the
switching regulator are premium-quality low-ESR capacitors and must be
replaced with equivalent types to ensure proper operation of the switch-
ing supply.
The output of the power supply is monitored by the power-indicator LED circuit,
which causes the power LED to flash according to a preset code to diagnose prob-
lems with the various power supplies in the 9400. See step (2.B) on page 4-8.
Abbreviations
Some of the abbreviations used in this manual may not be familiar to all readers:
A/D (or A to D) analog-to-digital converter
AES Audio Engineering Society
AGC automatic gain control
A-I analog input
A-O analog output
BAL balanced (refers to an audio connection with two active conductors and one shield sur-
rounding them).
BBC British Broadcasting Corporation
BNC a type of RF connector
CALIB calibrate
CIT composite isolation transformer
CMOS complementary metal-oxide semiconductor
COFDM Coded Orthogonal Frequency Division Multiplex — a robust type of digital modulation using
many narrow-bandwidth, low data rate, mutually non-interfering carriers to achieve an ag-
gregate high data rate with excellent multipath rejection.
COM serial data communications port
D/A (or D to A) digital-to-analog converter
dBm decibel power measurement. 0 dBm = 1mW applied to a specified load. In audio, the load
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