Synthesizer Troubleshooting; Table 9-7. Synthesizer Troubleshooting Chart - Motorola ASTRO SPECTRA Service Manual

9-12
NOTE: The P501 pins can be probed on the extender cable (see the P501 Extender Cable
9.7

Synthesizer Troubleshooting

The following table can help you troubleshoot problems that might occur in the synthesizer section of
your radio.
Symptom
Does Not Lock
on Any
Channel
Does Not Lock
on Some
Channels
Does Not Lock
in Tx (or
Talkaround
February 3, 2003
diagram on page 10-6 ).

Table 9-7. Synthesizer Troubleshooting Chart

Possible Cause
VCO
Reference Oscillator/RF
Board
VOCON Board
Programming
VCO
RF Board
RF Board
VCO
Basic Troubleshooting: Synthesizer Troubleshooting
Correction or Test (Measurements
Taken at Room Temperature)
With radio in receive mode, measure pin 1
of J601 using a high impedance probe.
Measured level should be -5 dBm ±6 dB,
and the frequency should be 370 to
380MHz.
If not, replace the VCO board.
Is there >1.5 Vp-p of 2.1 MHz on pin 21 of
J500?
If not, replace the RF board.
Do both the chip select lines (pins 16 & 20
of J500) go low during mode changes?
Is there data on the clock & data lines
going into the RF board (pins 18 & 19 of
J500)?
If not, replace the VOCON board.
Check the mode programming information
to ensure that the correct frequency
programming information has been
entered.
With the radio in receive mode; unplug the
loop feedback coax from the VCO board
to the RF board.
Measured level should be -5 dBm ±5 dB,
and the frequency should be 370 to 380
MHz.
If not, replace the VCO board.
Replace the RF board.
Check the Aux bit states (pin 9 & 11 J601).
When changing from receive to transmit to
talkaround, pin 9 and 11 of J601 should
alternate between a high voltage (>8V)
and a low voltage (<1V).
If either pin does not alternate between
these voltages, replace the RF board.
Replace the VCO board.
6881076C20-E