APEX
™
Exciter Incorporating FLO
™
Technology
Exciter Troubleshooting
Maintenance and Troubleshooting
26
04s50
0.fm
03/08/07
888-2604-001
Page: 5-19
WARNING: Disconnect primary power prior to servicing.
Additional information about the transport stream can be found at the Status > Digital
Processing > Flo FPGA Registers > Flo FPGA Status 3/5 Transport Stream Status screen.
If the quality of the input signal is suspect, a bitstream analyzer should be used to analyze
it, or a known good ASI transport signal source should be connected to the ASI input of the
exciter.
5.8
Exciter Troubleshooting
5.8.1
Frequency Error
Frequency accuracy is dependant on the accuracy of the 1st and 2nd local oscillators (LOs)
in the PLL board, which get their reference from the 10 MHz reference oscillator. The PLL
board 10 MHz oscillator is locked the external GPA 1PPS signal which enters the FPGA
modulator board. If a large frequency error exists, check the PLL status screen (second of
four IF & RF processing status screens). On this screen, the supply voltages should be
within tolerance (they will show a red fault or yellow warning if not in tolerance). Also
check the status of the IF PLL Lock (1st LO) and RF PLL Lock (2nd LO). They should
both be locked. The 10 PLL Lock and the 10 kHz reference statuses will read N/A since the
10 MHz oscillator is locked to the 1PPS signal via the FPGA modulator board, the
controller board, and the PLL board DAC.
If a fault exists in one or more of the PLLs and the power supply voltages are ok, a board
replacement should be tried.
If one or more of the supply voltages show warnings or faults, the problem may be on the
PLL board, UDC interface board, or power supply. Refer to Section 5.8.3 for additional
power distribution trouble shooting information.
Frequency measurement is covered in Section 5.1.2, Measuring PLL Board Frequencies,
on page 5-6.
5.8.2
Dark Screen
This problem assumes that the AC power is present, the power switch is on, and the fan is
operating.
The exciter display is completely dark and touching the display will not cause it to illumi-
nate (screen saver check) perform the following:
Note
The front panel display is controlled by the controller board (A8)
and the front panel display board (A10).
1
Check for the presence of supply voltages on the controller board by observing the fol-
lowing LEDs.
DS4 (green) indicates presence of +5 Vdc supply and DS1 (green) indicates the on
board regulator is pro3.3 Vdc. DS2 (red) indicates a 3.3 Vdc fault when illu-
minated. Further power supply voltage checks can be made by referring to Section
5.8.3, Power Supply Voltages on page 5-20.
2
Change the controller and/or the display boards.
