Maintenance
PSM-500/500L/500LT SCPC Satellite Modem
Page 4-6
PSM-500/500L/500LT - Rev. 0.91
Possible Cause
: The FIFO automatically re-centers when an overrun or under-run
condition occurs.
Action:
Check that the proper clocking options are used and the FIFO buffer is set large
enough to handle the expected satellite Doppler shift over a 24 hour period. No amount
of buffering will correct for different clocks on the input and output of the FIFO.
Possible Cause
: Receive signal or clock inverted.
Action:
Check the current state of the Demod Clock Phase. Try inverting the phase.
4.2.1 Onboard Diagnostic Indicators
There are 8 LEDs on the main PWB which provide diagnostic information about the status of
various functions:
1.
DS1
-
MBIT FAULT-
(Red) – Indicates that the transmit bit timing is not
synchronized. The most common reason for this fault should be that the modem is
set for external Transmit Timing input and either none is present or the applied signal
is off frequency.
2.
DS2
- MOD ENABLE
-
(Green) – Indicates that the modulator hardware has
enabled the transmit carrier.
3.
DS3
- Modulator FPGA program fault
-
(Red) – Indicates that the modulator
FPGA failed to program correctly.
4.
DS4
-
MSTP FAULT-
(Red) – Indicates that the transmit step synthesizer is
unlocked. Normally this would result only from an onboard fault.
5.
DS5
-
REF FAULT-
(Red) – Indicates that the onboard TCXO reference oscillator
is not phase locked when set to an external reference input.
6.
DS6
- System Clock Alarm
-
(Red) – Indicates that the 80 MHz clock hardware has
failed.
7.
DS7
-
DEM LOCK-
(Green) – Indicates that the demod hardware has locked to an
incoming carrier.
8.
DS8
-
DSTP FAULT-
(Red) – Indicates that the receive step synthesizer is unlocked.
Normally this would result only from an onboard fault.
9.
DS9
- Demodulator FPGA program fault
-
(Red) – Indicates that the demodulator
FPGA failed to program correctly.
10.
DS10
- I channel FPGA program fault
-
(Red) – Indicates that the I channel filter
failed to program correctly.
11.
DS11
- Q channel FPGA program fault
-
(Red) – Indicates that the Q channel
filter failed to program correctly.
12.
DS12
-
MLO FAULT-
(Red) – Indicates that the transmit Local Oscillator synthesizer
is unlocked. Normally this would result only from an onboard fault.
13.
DS13
-
DLO FAULT-
(Red) – Indicates that the receive Local Oscillator synthesizer
is unlocked. Normally this would result only from an onboard fault.
14.
DS14
- Front Panel FPGA program fault
-
(Red) – Indicates that the front panel
FPGA failed to program correctly.
