Motorola ASTRO Digital Spectra Plus Service Manual page 237

Troubleshooting Charts
Inject a 1kHz tone into MIC
with sufficient amplitude to
produce 3kHz of deviation,
PTT radio
Amplitude of
Measure waveform at
Waveform
TP208, should match
may vary
Figure 6-13
Measure waveform at R208
No
Waveform
(left) should match Figure 6-13
Correct?
Yes
Amplitude of
Waveform
may vary
Measure waveform at
Amplitude of
TP209, should match
Waveform
Figure 6-13
may vary
Waveform
Correct?
No
Yes
Measure waveform at J501-49
should match Figure 6-13 Measure waveform at C203
and C204, should match
Figure 6-14 Traces 1 and 2
Amplitude of
Waveform
may vary
Waveform No Inspect and repair
Correct?
J501
Yes
Amplitude of
Measure waveform at J501-48
Waveform
should match Figure 6-13
may vary
Inspect and repair
J501
No
Keyed 9.4V
Waveform
Correct?
Check for 5V at
J501-45
Yes
6881076C25-D
Inspect and Repair
Check 5V supply of U202-8
and GND U202-4
Yes
Waveform No
Measure waveform at
Correct?
should match Figure 6-13
Amplitude of
Waveform
may vary
Check 5V supply of U202-8
and GND U202-4
Yes
Waveform No
Correct?
Inspect J501
No
connections
No
Yes
Check for GND
Present? Present?
at J501-14
U202
No
Make sure the following components
Yes are placed and soldered correctly:
OK?
U202, R207, R208, C216, R209, R226,
C223, C217
Yes
Check that 3V is present at
No
U201-9
Waveform
U201-45, 31, 27, 3. Check
Correct? GND at U201-30, 28, 4
Inspect and repair
U202
No
Make sure the following components
Yes
are placed and soldered correctly:
OK?
U202, R202, R231, and C215
Check that 3V is present at
U201-45, 31, 27, 3. Check GND
at U201-30, 28, 4
Repair J501
No
OK?
Replace proper
components
Make sure the following parts
Yes
are the correct value: R207, Correct?
R208, R209, R226, R202,
R231, C216, C215
Repair proper
components
No
Yes
Replace U202
OK?
Yes
OK?
No
Repair U201
Repair proper
components
No
Yes
OK? Replace U202
Yes
OK?
No
Repair U201
Yes Continued on
B
next page
Replace proper
components
No
Make sure the following parts
Yes
are the correct value: R401,
Correct?
R408, R405, C405, C403,
R400, R407, C402, R438,
R437, R406, C404
Chart C.27 ASTRO Spectra Plus VOCON TX Modulation Failure Sheet 1 of 4
5-21
Continued on
A
next page
No
Yes
No trouble
found
October 28, 2002