6815854H01-A
June 15, 2005
Troubleshooting Procedures
: VHF (136–174 MHz) Band Main Board Troubleshooting
4-7
4.6.3
Out-of-Lock Condition
The probable cause of an out-of-lock condition is a failure in the synthesizer circuit. If the voltages on
the AUX 1*, AUX 2*, AUX3*, and AUX4* lines do not conform to required output frequency in
, troubleshoot the synthesizer.
If the AUX 1* to AUX 4* voltages are correct but the synthesizer feedback level is not within the
range indicated, troubleshoot the feedback path.
If the AUX 1* to AUX 4* voltages are correct and the synthesizer feedback level is correct but an
out-of-lock condition persists, troubleshoot the synthesizer.
4.6.4
FGU Troubleshooting Aids
The following illustrations are additional service aids for troubleshooting the frequency generation
unit.
•
is a block diagram of the DC distribution for the frequency generation
unit.
•
is a block diagram of the frequency generation unit.
•
describes the function of pins on the LV Frac-N IC U3751.
•
is a waveform representation during programming of the LV Frac-N IC
U3751.
Table 4-5. AUX Output Frequency Requirements
Frequency
Range
AUX 1
AUX 2
AUX 3
AUX 4
Output Frequency
HI
LOW
LOW
LOW
136–155 MHz
LOW
HI
LOW
LOW
155–174 MHz
LOW
LOW
HI
LOW
245.65–264.65 MHz
LOW
LOW
LOW
HIGH
264.65–283.65 MHz
Содержание XTL 1500
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