Motorola ASTRO SPECTRA Service Manual page 134

9-6
Symptom
No Modulation
Distorted
Modulation
February 3, 2003
Table 9-5. Transmitter Troubleshooting Chart (Continued)
Possible Cause
VCO Board
Command Board
VOCON Board
Bandwidth
Compensation Not Set/
Working
(DPL Distorted)
VOCON Board
Command Board
VCO Board
Basic Troubleshooting: Transmitter Troubleshooting
Correction or Test (Measurements
Taken at Room Temperature)
1. All modulation testing should be done
with the radio keyed and 1Vrms on the
microphone high line of the microphone.
2. Is radio properly tuned? (See Chapter
6. Radio Alignment Procedure.)
3. Is there > 400 mVrms at J500 pin 11?
If so, replace the VCO board.
If there is > 400 mVrms (ac coupled) at
P501 pin 49 and not at J500 pin 11,
replace the command board.
If there is >200 mVrms modulation at J501
pin 39 and no modulation at J501 pin 49,
replace the VOCON board.
Is the correct bandwidth selected (use the
appropriate radio programming software)?
Is radio properly tuned?
Chapter 6: Radio Alignment
(See
Procedure
.)
Check compensation setting.
If compensation won't adjust, go to Can't
Set Compensation below.
With 80 mVrms on the mic high line, is the
signal on pin 49 of P501 distorted (ac
coupled)?
If so, replace the VOCON board.
With 80 mVrms on the mic high line, is the
output of the command board VCO Mod
(pin 11 of J500) distorted?
If so, replace the command board.
Replace VCO board.
6881076C20-E