Motorola ASTRO SPECTRA Service Manual page 141

Basic Troubleshooting: Synthesizer Troubleshooting
Symptom
Synthesizer
Malfunctioning
6881076C20-E
Table 9-7. Synthesizer Troubleshooting Chart (Continued)
Possible Cause
Synthesizer Not Locked
Reference Oscillator
Not On Frequency/
Working
VOCON Board
Programming
(EEPROM)
RF Board
Correction or Test (Measurements
Taken at Room Temperature)
Check the synthesizer lock line (pin 14 of
J500).
If > 1 V, then the synthesizer is not locked.
Go to Does Not Lock on Some Channels
above.
1. Check the reference oscillator
frequency.
It should be 16.8 MHz ±4 Hz.
THIS MUST BE MEASURED @ 25° C
(77° F) TO BE ACCURATE.
2. Retune the reference oscillator if
frequency is incorrect.
If the reference oscillator will not tune on
frequency, is reference control voltage (pin
2 of J500) tuning 1.5 to 3.0 volts, and is
the 5 volt supply 5 V ±.2 V? If not, replace
the VOCON board.
Check mode programming information to
ensure that the correct frequency
programming information has been
entered.
Replace the RF board.
9-13
February 3, 2003