Out-Of-Lock Condition; Fgu Troubleshooting Aids; Table 4-5. Aux Output Frequency Requirements - Motorola ASTRO XTL 1500 Detailed Service Manual

Troubleshooting Procedures: VHF (136–174 MHz) Band Main Board Troubleshooting
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
Table 4-5, 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.
Frequency
Range
4.6.4

FGU Troubleshooting Aids

The following illustrations are additional service aids for troubleshooting the frequency generation
unit.
• Figure 4-1 on page 4-8
unit.
• Figure 4-2 on page 4-9
• Table 4-6 on page 4-9
• Figure 4-3 on page 4-11
U3751.
6815854H01-A

Table 4-5. AUX Output Frequency Requirements

AUX 1 AUX 2
HI LOW
LOW HI
LOW LOW
LOW LOW
is a block diagram of the DC distribution for the frequency generation
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
AUX 3 AUX 4
LOW LOW 136–155 MHz
LOW LOW 155–174 MHz
HI LOW 245.65–264.65 MHz
LOW HIGH 264.65–283.65 MHz
Output Frequency
June 15, 2005
4-7