Nautel NX15, Руководство по устранению неисправностей

Страница: 81 / 274

NX25/NX15 Troubleshooting Manual Detailed Circuit Descriptions
Issue 5.0 2016-05-06 Page 2-3
Synchronization input selection
Various synchronization inputs (1 PPS, 1 kHz and 10 MHz) can be applied to the control/interface
PWB. Selection circuits determine which sources (A or B, then internal or external) provide the
signals applied to the digital AM exciter PWBs via connectors J17 (exciter A) and J19 (exciter B).
1 PPS, 1 kHz and 10 MHz inputs from the optional GPS sync PWBs [A11A5 (A) and A11A6 (B)] are
applied to connectors J5A and J5B respectively. Multiplexer U44 selects which sync inputs are passed
based on the status of the
Select Sync B input on U44-1. Shorting jumper E1 must be installed in the
EXT
position (shorting pins 1 and 2).
Multiplexer U45 selects either internal or external sync inputs based on the status of the Select Sync Int
input on U45-1. For internal input selection, the inputs from the selected GPS sync PWB (from
multiplexer U44) are applied to the digital AM exciter PWBs. For external input selection, the
externally sourced 1 PPS (J9) and 10 MHz (J8) inputs are applied to the digital AM exciter PWBs.
Remote inputs and outputs
The user can interface with up to 16 pre-defined digital inputs, 16 digital outputs and four analog
outputs via the remote interface PWB (A11A4) (see
“Remote interface PWB (NAPI106)” on page 2-
8 ). The control/interface PWB configures these inputs and outputs based on customer interface with
the AUI. These inputs and outputs may be user-defined or factory defaulted (see the NX300
Installation Manual for default settings).
Digital inputs
RFI filtering is provided on all digital input lines to ensure transmitter operation is not interrupted
due to RF pick up on control lines. Opto-couplers buffer/isolate the external circuits and prevent
unwanted transients from affecting transmitter operation. The digital inputs on connector J24 are
shifted in through shift registers U76 and U74. These values are then relayed to microcontroller U57
over the SPI bus.
Digital outputs
Shift registers U77 and U78, controlled by microcontroller U57 over the SPI bus, control the status
of the digital outputs applied to connector J23. Digital output logic levels are configured through the
AUI.
Analog outputs
Digital samples of the selected (or defaulted) analog outputs are applied to DAC U72 by
microcontroller U57 over the SPI bus. The analog outputs of DAC U72 are applied to connector J23,
via operational amplifiers U79:A through U79:D.