No Rx Audio - Motorola ASTRO Digital Spectra Service Manual

5-14
Isolate and
repair problems,
See Chart C.5.
During a mode change,
verify an ABACUS
programming sequence
occurs per Fig. W4,
probing on the
ABACUS carrier.
Verify SBI signal
connection between
No
ADSIC and ABACUS ABACUS is
programmed?
ICs; repair as necessary.
If connection is good
replace U406.
Yes
Fault lies with RF
board. Refer to
appropriate section,
Chart C.1.
Chart C.19 No RX Audio
July 1, 2002
No Receive Audio
Set radio to test mode CSQ.
Inject a 1KHz modulated
signal at the carrier.
Frequency at -60dBm level
with 3KHz deviation.
Verify standard
bias per Table 6.
Check for continuity between
U405 and U406 of the
signals depicted in Fig. W2
and the 8KHz IRQB.
No
Standard
bias OK?
Yes
Verify signals present at
ADSIC (U406) per Fig. W10
and Fig. W5. Note DOUT
and DOUT* are low-level
voltage signals.
Repair connections.
No
Signals
present?
No
Yes
Fig. W7-
Yes
Trace 3 or 4
Trace 2
Verify signals per
present or in
present?
Fig. W7 at points
indicated.
Yes
Check for continuity
from U406 to C412.
Fig. W7-
No
Signals Check for shorts and
Trace 1
present? check C412.
present?
Yes No
Replace U406.
Verify signals per
Fig. W2 at points
indicated.
No
Signals
Replace U406.
present?
Yes
Perform radio functions,
Yes
Connections
which causes an alert
good?
tone to be generated.
No
Yes
Alert tone
Replace U406.
audible?
No
Replace U405.
Fig. W7-
Yes
phase?
No
Verify signal
at output of
U524 pin 2.
Verify signal
No
Signal
at input of
present?
U524 pin 1.
Yes
Yes
Signal
Verify control
Verify signal
present?
lines to U524.
present at
U450 pin 2.
No
Signals
Repair connection
present?
from C412 to U524.
Check for
No
Signal
Yes
continuity from
present?
U524 to U450.
Replace U524.
Yes
Verify signals
present at U450
pins 11 and 13.
This failure indicates a lack of
received audio with the fault lying
with the VOCON or Command
board. It assumes a functional
transceiver and no power
Repair connection
Yes
Signals
up fail codes were displayed.
from U450 to
present?
Since all received signal modes
speaker terminals.
occur through this same path,
this failure applies to digital/
No
PL,DPL, etc. Failure modes are
as follows:
1) Missing DSP IRQB interrupt.
Verify control
2) Lack of 2.4 REF clock and/or
and supply
data from ABACUS.
for U450.
3) Missing clock or data on SSI
port from ADSIC.
4) Non-functional control of or
faulty Audio PA.
5) Faulty ADSIC.
Signals Yes
Replace U450.
present?
No
Troubleshoot
control or
supply lines.
Troubleshooting Charts
Troubleshoot
No
control or
supply lines.
Synopsis
MAEPF-26075-O
68P81076C25-C